JP7553271B2 - Polyhydric hydroxyl resin, its production method, epoxy resin composition containing same, and cured epoxy resin product - Google Patents

Description

The present invention relates to polyhydric hydroxyl resins, their manufacturing methods, and epoxy resin compositions and cured epoxy resin products using them. More specifically, the present invention relates to polyhydric hydroxyl resins that are useful as insulating materials for electric and electronic components such as semiconductor encapsulation, laminates, and heat dissipation substrates, and that have excellent handleability as a solid at room temperature, low viscosity during molding, and solvent solubility, their manufacturing methods, and epoxy resin compositions, as well as cured epoxy resin products obtained by curing them and that have excellent thermal conductivity, heat resistance, and low thermal expansion.

In recent years, electronic devices have been designed to achieve high-density mounting of semiconductor packages, high integration and high speed of LSIs, and so materials with higher dimensional stability are required. Furthermore, with the progress of single-sided mounting of packages, reducing package warpage has become an important issue, and the development of resins with lower thermal expansion is required. In response to the above trends, heat dissipation measures for heat generated by elements have become a very important issue. In particular, in the field of power devices, heat generation from electronic circuits has increased, and the heat dissipation properties of cured resins used in insulating parts have become an issue. Conventionally, this heat dissipation was achieved by the thermal conductivity of the filler, but in order to achieve even higher integration, there is a demand for improving the thermal conductivity of the matrix resin itself.

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 whose essential components are a biphenol-type epoxy resin and a polyhydric phenol resin curing agent, and discloses that the composition has excellent stability and strength at high temperatures and can be used in a wide range of fields such as adhesion, casting, sealing, molding, and lamination. Patent Document 2 discloses an epoxy compound that has two mesogenic structures linked by a bent chain in the molecule. Furthermore, Patent Document 3 discloses a resin composition that contains an epoxy compound with a mesogenic group.

However, epoxy resins with such mesogenic structures have a high melting point, and when they are mixed, the high melting point component is difficult to dissolve and remains undissolved, resulting in problems with reduced curability and heat resistance. Also, high temperatures are required to mix such epoxy resins uniformly with the curing agent. At high temperatures, the curing reaction of the epoxy resin proceeds rapidly and the gelation time is shortened, so the mixing process is severely restricted and handling is difficult. If a soluble third component is added to compensate for this drawback, the melting point of the resin decreases and uniform mixing becomes easier, but the cured product has a problem of reduced thermal conductivity.

As a highly thermally conductive resin 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 solubility in solvents, and their applications are limited.

Patent Document 6 discloses an epoxy resin composition using a phenolic compound having a diphenyl ester structure, but because of its high melting point, it is difficult to melt and knead uniformly, and fine pulverization by jet mill grinding or the like is necessary. Also, because of its poor solvent solubility, it is difficult to apply it to substrates or sheets that require varnish formation. In addition, Patent Document 7 discloses a bifunctional ester group-containing phenol of hydroquinone and p-hydroxybenzoic acid, but because of its high crystallinity, there are problems with solvent solubility and melt kneadability.

Japanese Unexamined Patent Publication No. 7-90052 Japanese Patent Application Publication No. 9-118673 Japanese Patent Application Publication No. 11-323162 WO2009/110424 JP 2010-43245 A JP 2010-184993 A US4762901 publication

The object of the present invention is therefore to provide a polyhydric hydroxyl resin that can be used to solve the above problems, has excellent handleability as a solid at room temperature, and has low viscosity during molding and 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 that has excellent reliability, a method for producing the same, an epoxy resin composition containing the same, and a cured epoxy resin product.

Through extensive research, the inventors have discovered that a polyhydric phenol resin having a specific ester group is expected to solve the above problems, and that the cured product exhibits an effect on thermal conductivity.

〔ここで、ＸはＯＨ基または式（ａ）で表される一価の置換基を表し、ｎは０より大きく２０以下の数を示す。〕

（ここで、Ｙは炭素数６～１２の芳香族炭化水素基を示し、Ｒは水素原子または炭素数１～６の炭化水素基を示し、ｐは１～３の数を示す。） That is, the present invention relates to a polyhydric hydroxy resin represented by the following general formula (1), which contains at least one ester structure.

[wherein, X represents an OH group or a monovalent substituent represented by formula (a), and n represents a number greater than 0 and less than or equal to 20.]

(Here, Y represents an aromatic hydrocarbon group having 6 to 12 carbon atoms, R represents a hydrogen atom or a hydrocarbon group having 1 to 6 carbon atoms, and p represents a number from 1 to 3.)

The polyhydroxy resin preferably has a number average molecular weight of 3,000 or less.

（ここで、ｎは０より大きく２０以下の数を示す。）

（ここで、Ｙは炭素数６～１２の芳香族炭化水素基を示し、ＲおよびＲ^１はそれぞれ独立して水素原子または炭素数１～６の炭化水素基を示し、ｐは１～３の数を示す。） The present invention also relates to a method for producing the above-mentioned polyhydric hydroxy resin, which comprises reacting 0.1 to 0.7 moles of an OH-containing ester represented by general formula (3) with 1 mole of OH groups of the polyhydric hydroxy resin represented by general formula (2).

(Here, n is a number greater than 0 and less than or equal to 20.)

(wherein Y represents an aromatic hydrocarbon group having 6 to 12 carbon atoms, R and ^R1 each independently represent a hydrogen atom or a hydrocarbon group having 1 to 6 carbon atoms, and p represents a number from 1 to 3.)

The present invention also relates to an epoxy resin composition comprising an epoxy resin and a curing agent, characterized in that any of the polyhydric hydroxyl resins described above is used as an essential component as part or all of the curing agent.

The epoxy resin in the epoxy resin composition of the present invention is preferably a bifunctional crystalline epoxy resin.

The present invention further relates to an epoxy resin cured product obtained by curing the above-mentioned epoxy resin composition.

The polyhydric hydroxy resin of the present invention and the epoxy resin composition using the same have excellent solvent solubility, moldability, and reliability, and the cured product exhibits excellent high thermal conductivity. In addition, by suppressing crystallinity, the yield is improved, which is advantageous in terms of production. Furthermore, it has been found that the hydroquinone-based polyhydric hydroxy resin, which is the basic skeleton, has the effect of suppressing the increase in molecular weight due to self-polymerization during esterification. This makes it possible to control the molecular weight and esterification ratio, which is usually difficult.

FIG. 1 is a GPC chart of the ester group-containing polyhydric hydroxy resin (Example 1). FIG. 2 is an IR chart of the ester group-containing polyhydric hydroxy resin (Example 1). FIG. 3 is an FD-MS spectrum of the ester group-containing polyhydric hydroxy resin (Example 1).

The present invention is described in detail below.

The polyhydric hydroxy resin of the present invention is represented by the above general formula (1) and contains at least one ester structure represented by formula (a). n is the number of repetitions (number average) and is a number greater than 0 and less than 20. The component with n=0 has the strongest crystallinity and excellent orientation, but low solvent solubility, so it is preferably a mixture of components with different n values. Furthermore, components with large n have high viscosity, reduce fluidity, and require a long time to dissolve in a solvent due to self-aggregation, so it is more preferable to use a mixture of components with n greater than 0 and less than 10. The molecular weight is preferably 3,000 or less in number average molecular weight.

The ester structure, which is a monovalent substituent, is represented by the above formula (a), where Y represents an aromatic hydrocarbon having 6 to 12 carbon atoms, R represents a hydrogen atom or a hydrocarbon group having 1 to 6 carbon atoms, and p represents a number from 1 to 3. Preferred structures for Y are a benzene ring, a naphthalene ring, and a biphenyl structure. Furthermore, the more rigid the polycyclic aromatic, the more it contributes to orientation and thermal stability, but the more the solvent solubility decreases and it becomes difficult to achieve both with reactivity, so a more preferred structure is a benzene ring. In structures where the number of OH groups in the monovalent substituent is 2 or more, the reaction control becomes complicated and abrupt, and it is also difficult to universally supply raw materials, so p is more preferably 1.

The polyhydric hydroxy resin containing an ester structure represented by the above general formula (1) can be obtained by reacting the polyhydric hydroxy resin represented by the above general formula (2) with the OH group-containing ester represented by the above general formula (3) under an acid catalyst. For this reaction, normal esterification conditions can be appropriately adopted. Here, the polyhydric hydroxy resin represented by the general formula (2) can be obtained from a condensation reaction of hydroquinone and formaldehyde. The manufacturing method is a general phenol resin manufacturing method, and paraform or formalin may be used as formaldehyde, and the reaction may be carried out under an acid catalyst. The ratio of formaldehyde used as a condensation agent to 1 mole of OH groups of hydroquinone is preferably in the range of 0.1 to 0.5 moles, more preferably in the range of 0.2 to 0.4 moles. If it is more than 0.5 moles, the viscosity increases and the solvent solubility decreases, making it difficult to handle. If the amount is less than 0.1 mol, the amount of the polymerizable component is small, and a large amount of unreacted monomer remains, which may result in a decrease in the heat resistance, thermal conductivity, mechanical strength, etc. of the cured product. In addition, when removing a large amount of unreacted hydroquinone, a high-temperature and high-pressure process is required, which is also a problem in terms of production, so the above range is preferable. In addition, the OH group-containing ester represented by the general formula (3) includes p-hydroxybenzoic acid, 4-hydroxy-2-methylbenzoic acid, 4-hydroxy-3-methylbenzoic acid, 2,4-dihydroxybenzoic acid, 3,4-dihydroxybenzoic acid, 6-hydroxy-2-naphthoic acid, 3,5-dihydroxy-2-naphthalenecarboxylic acid, and 4-(4-hydroxyphenyl)benzoic acid, and the carboxylic acid ester includes methyl p-hydroxybenzoate, ethyl p-hydroxybenzoate, methyl 6-hydroxy-2-naphthoate, ethyl 6-hydroxy-2-naphthoate, and methyl 4'-hydroxy[1,1'-biphenyl]-4-carboxylate, and the like, with p-hydroxybenzoic acid and methyl p-hydroxybenzoate being preferred in terms of reactivity and solvent solubility. As the modification rate of the esterification in these reactions, it is preferable to react 0.1 to 0.7 moles of the OH group-containing ester represented by the general formula (3) with 1 mole of OH group of the polyhydric hydroxy resin represented by the general formula (2). If the amount is less than 0.1 mol, the effect of promoting orientation is small, and improvement in thermal conductivity during curing cannot be expected. On the other hand, if the amount is more than 0.7 mol, steric hindrance becomes large, which is one of the factors that causes irregular orientation, and is not preferable. In addition, partial esterification is preferable because self-polymerization of OH-containing carboxylic acids is likely to occur as a side reaction. More preferably, the range of 0.4 to 0.6 mol is preferable from the viewpoint of improving the thermal conductivity of the cured product.

The epoxy resin composition of the present invention is an epoxy resin composition containing an epoxy resin and a curing agent, and is formulated with a polyhydric hydroxyl resin represented by the above general formula (1) as an essential component as part or all of the curing agent.

The amount of epoxy resin to be used is determined by taking into consideration the equivalent balance with the OH groups of the curing agent. For 1 equivalent of epoxy groups, the OH groups of the curing agent generally range from 0.5 to 2.0 equivalents, and preferably ranges from 0.7 to 1.5 equivalents. Outside this range, unreacted monomers will remain, which may reduce the heat resistance, thermal conductivity, mechanical strength, etc. of the cured product.

In addition to the polyhydric hydroxyl resin of the present invention represented by the general formula (1), other types of curing agents may be blended in the epoxy resin composition as a curing agent component, and all commonly known curing agents can be used. Examples of such other types of curing agents include dicyandiamide, polyhydric phenols, acid anhydrides, aromatic and aliphatic amines, etc. Specific examples of polyhydric phenols include dihydric phenols such as bisphenol A, bisphenol F, bisphenol S, fluorene bisphenol, 4,4'-biphenol, 2,2'-biphenol, hydroquinone, resorcin, 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 by condensing dihydric phenols such as phenols, naphthols, bisphenol A, bisphenol F, bisphenol S, fluorene bisphenol, 4,4'-biphenol, 2,2'-biphenol, hydroquinone, resorcin, and naphthalenediol with formaldehyde, acetaldehyde, benzaldehyde, p-hydroxybenzaldehyde, and p-xylylene glycol.

Acid anhydrides include phthalic anhydride, tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, hexahydrophthalic anhydride, methylhexahydrophthalic anhydride, methylhimic anhydride, nadic anhydride, trimellitic anhydride, etc.

Furthermore, the amines 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.
In the resin composition of the present invention, one or more of these curing agents can be used in combination. In the case of the epoxy resin composition of the present invention, the amount of the polyhydric hydroxyl resin represented by the general formula (1) is preferably in the range of 5 to 100 wt %, and more preferably 60 to 100 wt %, of the total amount of the curing agent. From the viewpoint of reliability and thermal conductivity of the cured product, the other curing agent is preferably a dihydric phenol, and more preferably 4,4'-biphenol, 2,2'-biphenol, hydroquinone, resorcin, naphthalenediol, or 4,4'-dihydroxydiphenyl ether.

As the epoxy resin component in the epoxy resin composition of the present invention, any ordinary epoxy resin having two or more epoxy groups in the molecule can be used. 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, resorcinol, catechol, t-butyl catechol, etc. 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 Naphthalene, allyl or polyallyl products of the above dihydroxynaphthalene, dihydric 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-tetrakis Examples of such epoxy resins include glycidyl ethers derived from trivalent or higher phenols such as (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-based resins, or halogenated bisphenols such as tetrabromobisphenol A. These epoxy resins can be used alone or in combination of two or more.

To obtain a cured product with excellent thermal conductivity, bifunctional epoxy resins with strong crystallinity are preferred. For example, glycidyl ethers derived from dihydric phenols such as 4,4'-biphenol, 2,2'-biphenol, hydroquinone, resorcinol, and 4,4'-dihydroxyphenyl ether. In particular, those containing epoxidized 4,4'-biphenol are preferred.

In the epoxy resin composition of the present invention, oligomers or polymeric compounds such as polyester, polyamide, polyimide, polyether, polyurethane, petroleum resin, indene resin, indene-cumarone resin, and phenoxy resin may be appropriately blended as other modifiers. 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.

Additives such as inorganic fillers, pigments, flame retardants, thixotropy agents, coupling agents, and flow improvers can be blended into the epoxy resin composition of the present invention. Examples of inorganic fillers include silica powders such as spherical or crushed fused silica and crystalline silica, alumina powders, glass powders, mica, talc, calcium carbonate, alumina, and alumina hydrate. When used as a semiconductor encapsulant, the preferred blending amount is 70% by weight or more, and more preferably 80% by weight or more.

Pigments include organic or inorganic extender pigments, scaly pigments, etc. Thixotropic agents include silicone-based, castor oil-based, aliphatic amide wax, oxidized polyethylene wax, organic bentonite-based, etc.

Furthermore, a curing accelerator can be used in the epoxy resin composition of the present invention as needed. Examples of the organic phosphines include amines, imidazoles, organic phosphines, Lewis acids, and the like. Specific examples of the organic phosphines include tertiary 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; organic phosphines such as tributylphosphine, methyldiphenylphosphine, triphenylphosphine, diphenylphosphine, and phenylphosphine; tetra-substituted phosphonium tetra-substituted borates such as tetraphenylphosphonium tetraphenylborate, tetraphenylphosphonium ethyltriphenylborate, and tetrabutylphosphonium tetrabutylborate; and 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.

If necessary, the epoxy resin composition of the present invention may further contain 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, stress reducers such as silicone oil, and lubricants such as calcium stearate.

The epoxy resin composition of the present invention can be made into a varnish state by dissolving an organic solvent in it, and then impregnating it into a fibrous material such as glass cloth, aramid nonwoven fabric, or polyester nonwoven fabric made of liquid crystal polymer, etc., followed by removing the solvent to form a prepreg. In some cases, it can also be made into a laminate by applying it onto a sheet-like material such as copper foil, stainless steel foil, polyimide film, or polyester film.

The epoxy resin composition of the present invention can be heated and cured to produce the cured resin of the present invention. This cured product can be obtained by molding the epoxy resin composition using known methods such as casting, compression molding, and transfer molding. The temperature used for this is usually in the range of 100 to 220°C.

The present invention will be specifically explained below with reference to synthesis examples, working 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 % by weight. In addition, the measurements were performed by the following methods.

1) Measurement of OH equivalent: Approximately 6 mg/eq of sample was precisely weighed into a 100 mL stoppered flask, 3 mL of a mixed reagent of acetic anhydride/pyridine = 3/1 (volume ratio) was added, a cooling tube was attached, the mixture was heated to reflux on a hot plate for 5 minutes, and after cooling for 5 minutes, 1 mL of water was added. The solution was titrated potentiometrically with a 0.5 mol/L KOH/MeOH solution to calculate the OH equivalent.

2) Measurement of epoxy equivalent: Using a potentiometric titrator, methyl ethyl ketone was used as a solvent, and a tetraethylammonium bromide acetate solution was added. The epoxy equivalent was measured using a 0.1 mol/L perchloric acid-acetic acid solution in the potentiometric titrator.

3) Melting point The DSC peak temperature was determined using a differential scanning calorimeter (EXSTAR6000 DSC/6200 manufactured by SII NanoTechnology Inc.) at a temperature rise rate of 5° C./min. That is, this DSC peak temperature was defined as the melting point of the resin.

4) Melt Viscosity The melt viscosity was measured at 150° C. using a CAP2000H rotational viscometer manufactured by BROOKFIELD.

5) Softening point: Measured by the ring and ball method in accordance with JIS-K-2207.

6) GPC Measurement A main body (HLC-8220GPC, manufactured by Tosoh Corporation) equipped with columns (TSKgel G4000HXL, TSKgel G3000HXL, TSKgel G2000HXL, manufactured by Tosoh Corporation) in series was used, and the column temperature was set to 40°C. Tetrahydrofuran (THF) was used as the eluent, the flow rate was set to 1 mL/min, and a differential refractive index detector was used as the detector. The measurement sample was 50 μL of a sample obtained by dissolving 0.1 g of sample in 10 mL of THF and filtering through a microfilter. Data processing was performed using GPC-8020 Model II Version 6.00 manufactured by Tosoh Corporation. The number average molecular weight (Mn) was also determined from a calibration curve using standard polystyrene.

7) Glass transition temperature (Tg)
The Tg was determined using a thermomechanical measurement device (EXSTAR6000TMA/6100 manufactured by SII NanoTechnology Inc.) at a temperature increase rate of 10° C./min.

8) 10% weight loss temperature (Td10), carbon residue ratio Using a thermogravimetric/differential thermal analyzer (EXSTAR6000TG/DTA6200, manufactured by SII Nano Technology), the 10% weight loss temperature (Td10) was measured under conditions of a nitrogen atmosphere and a heating rate of 10°C/min. The weight loss at 700°C was also measured and calculated as the carbon residue ratio.

9) Thermal Conductivity The thermal conductivity was measured by a non-steady hot wire method using a NETZSCH LFA447 type thermal conductivity meter.

10) Infrared Absorption (IR) Measurement The absorbance at wave numbers of 400 to 4000 cm ⁻¹ was measured by the attenuated total reflection method (ATR method) using a Fourier transform infrared spectrophotometer (Frontier Gold FT-IR Spectrometer, manufactured by Perkinelmer Inc.).

11) Field desorption ionization mass spectrometry (FD-MS)
The measurement was performed using a mass spectrometer JMS-T100GCV (manufactured by JEOL Ltd.) The sample was dissolved in acetone and subjected to the measurement.

Reference Example 1
In a flask equipped with a Dean-Stark tube, 300.0 g of hydroquinone, 28.9 g of paraformaldehyde, and 263.1 g of diethylene glycol dimethyl ether were charged, and the mixture was heated to about 100°C while stirring under a nitrogen stream to dissolve. Next, 0.33 g of p-toluenesulfonic acid was added, and the mixture was heated to 160°C and reacted for 6 hours while dehydrating to produce a polyhydric hydroxy resin. Diethylene glycol dimethyl ether was distilled off, methyl isobutyl ketone was added, and the mixture was neutralized, washed with water, and filtered, and then methyl isobutyl ketone was distilled off under reduced pressure to obtain 295.1 g of polyhydric hydroxy resin a according to general formula (2). The OH equivalent of this polyhydric hydroxy resin a was 59 g/eq. The number average molecular weight was 430, and it was a mixture with n (number average) of 0 to 5.

Example 1
50.0 g (about 0.85 mol) of the polyhydric hydroxy resin a obtained in Reference Example 1, 58.5 g (about 0.42 mol) of p-hydroxybenzoic acid, 200.0 g of chlorobenzene, and 1.9 g of p-toluenesulfonic acid were charged, and the mixture was heated to 120° C. under stirring under a nitrogen stream, and reacted for 5 hours while refluxing and dehydrating the water in the system. After cooling to room temperature, filtration, repeated washing with water, and drying under reduced pressure were performed to obtain 44.9 g of ester group-containing polyhydric hydroxy resin A in the form of a yellowish brown powder. The number average molecular weight was 484, and n (number average) was a mixture of 0 to 5. The content (GPC area%) of n=0 was 11 area%. The GPC chart is shown in FIG. 1, the IR chart is shown in FIG. 2, and the FD-MS spectrum is shown in FIG. 3. The melting point by DSC was confirmed to have three peak temperatures of 177° C., 193° C., and 247° C. The OH equivalent was calculated from the results of analyzing each component by the charging ratio, GPC and FD-MS, and was found to be 119 g/eq.

Example 2
The reaction was carried out in the same manner as in Example 1, except that 79.7 g (about 0.42 moles) of 6-hydroxy-2-naphthoic acid was used instead of p-hydroxybenzoic acid, to obtain 87.9 g of a brown powdery ester group-containing polyhydric hydroxy resin (polyhydric hydroxy resin B). The calculated OH equivalent of this resin was 156 g/eq.

Reference Example 2
In a flask equipped with a Dean-Stark tube, 50.0 g of hydroquinone, 39.9 g of p-hydroxybenzoic acid, 0.75 g of boric acid, 3.1 g of sulfuric acid, and 400 g of xylene were charged, and the mixture was heated to 130°C under stirring under a nitrogen stream, and reacted for 5 hours while refluxing and dehydrating the water in the system. After cooling to room temperature, the mixture was filtered and neutralized, and then repeatedly washed with water, and further washed with methanol, followed by drying under reduced pressure to obtain 54.1 g of white crystals. The calculated OH equivalent was 115 g/eq., and the melting point by DSC was 240°C.

Reference Example 3
50.0 g of hydroquinone and 100.0 g of 4,4'-dihydroxybiphenyl were dissolved in 1000 g of epichlorohydrin and 150 g of diethylene glycol dimethyl ether, and 16.5 g of 48% sodium hydroxide was added at 60°C and stirred for 1 hour. Then, 148.8 g of 48% aqueous sodium hydroxide solution was added dropwise over 3 hours under reduced pressure (about 130 Torr). During this time, the water generated was removed from the system by azeotropy with epichlorohydrin, and the distilled epichlorohydrin was returned to the system. After the dropwise addition was completed, the reaction was continued for another 1 hour to dehydrate, and then epichlorohydrin was distilled off, 600 g of methyl isobutyl ketone was added, and salt was removed by washing with water. Then, 13.5 g of 48% sodium hydroxide was added at 85°C, stirred for 1 hour, and washed with 200 mL of warm water. Thereafter, water was removed by separation, and methyl isobutyl ketone was distilled off under reduced pressure to obtain 224 g of a white crystalline modified epoxy resin (epoxy resin A). The epoxy equivalent was 138, the hydrolyzable chlorine content was 320 ppm, and the melting point by the capillary method was 10
The temperature ranged from 4°C to 141°C, and the viscosity at 150°C was 3.4 mPa·s.

Examples 3 to 7, Comparative Examples 1 to 5
As the epoxy resin component, the epoxy resin of Reference Example 3 (epoxy resin A), an epoxidized product of 4,4'-dihydroxydiphenyl ether (epoxy resin B: manufactured by Nippon Steel Chemical & Material Co., Ltd., YSLV-80DE 163 g/eq.), a biphenyl-based epoxy resin (epoxy resin C: manufactured by Japan Epoxy Resins, YX-4000H, epoxy equivalent 188 g/eq.), or a phenol novolac-type epoxy resin (epoxy resin D: manufactured by Nippon Steel Chemical & Material Co., Ltd. Terial Co., Ltd., YDPN-638, epoxy equivalent 177 g/eq.) was used, and as the curing agent, the polyhydric hydroxy resin A of Example 1 (curing agent A), the polyhydric hydroxy resin B of Example 2 (curing agent B), the polyhydric hydroxy resin a of Reference Example 1 (curing agent C), hydroquinone (curing agent D), phenol novolac resin (curing agent E: hydroxyl equivalent 105, softening point 67°C), or the reaction product of hydroquinone and p-hydroxybenzoic acid of Reference Example 2 (curing agent F) was used. In addition, triphenylphosphine was used as a curing accelerator to obtain an epoxy resin composition with the formulation shown in Table 1. The numerical values in the table indicate the parts by weight in the formulation. This epoxy resin composition was used to mold at 175°C, and post-cured at 175°C for 5 hours to obtain a cured product test piece, which was then subjected to various physical property measurements.

As is clear from these results, the epoxy resin compositions obtained in the examples have excellent moldability, and the cured products thereof have good thermal conductivity, heat resistance and low thermal expansion, and are therefore suitable for use in power devices and automotive applications.

Claims (6)

A polyhydric hydroxy resin represented by the following general formula (1), characterized in that it contains at least one ester structure:

[wherein, X represents an OH group or a monovalent substituent represented by formula (a), at least one of which is represented by formula (a); n represents the repeat number (number average) and indicates a mixture of components greater than 0 and not greater than 20 ; and the proportion of n=0 components in GPC measurement is 11 area % or less .]

(Here, Y represents an aromatic hydrocarbon group having 6 to 12 carbon atoms, R represents a hydrogen atom or a hydrocarbon group having 1 to 6 carbon atoms, and p represents a number from 1 to 3.) The polyhydric hydroxyl resin according to claim 1, having a number average molecular weight of 3,000 or less. A method for producing the polyhydric hydroxy resin according to claim 1 or 2, comprising the steps of:
A method for producing a polyhydric hydroxy resin, comprising reacting 0.1 to 0.7 moles of an OH group-containing ester represented by general formula (3) with 1 mole of OH groups of a polyhydric hydroxy resin represented by general formula (2).

(Here, n is the repeat number (number average) and indicates a mixture of components greater than 0 and not greater than 20 , and the amount of n=0 components in GPC measurement is 11 area % or less .)

(wherein Y represents an aromatic hydrocarbon group having 6 to 12 carbon atoms, R and ^R1 each independently represent a hydrogen atom or a hydrocarbon group having 1 to 6 carbon atoms, and p represents a number from 1 to 3.) An epoxy resin composition comprising an epoxy resin and a curing agent, the epoxy resin composition being characterized in that the polyhydric hydroxyl resin according to claim 1 or 2 is used as part or all of the curing agent. The epoxy resin composition according to claim 4, characterized in that the epoxy resin is a difunctional crystalline epoxy resin. An epoxy resin cured product obtained by curing the epoxy resin composition according to claim 4 or 5.

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