JPH0920819A - Modified phenol novlak resin, epoxy resin, epoxy resin composition and its cured product - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject resins, capable of providing a cured product having both adhesion and water resistance and useful as a molding, a casting, a laminating and a coating materials, an adhesive, a resist, etc., by carrying out the addition reaction of phenol novolaks with dicyclopentadiene in the presence of an acidic catalyst. SOLUTION: This modified phenol novolak resin of formula II (P is H or CH2 ) is obtained by carrying out the addition reaction of phenol novolaks of formula I [(n) is a positive number and an average value; R is H, a halogen, a 1-8C alkyl or an aryl] with dicyclopentadiene in the presence of an acidic catalyst. The hydroxyl groups thereof are glycidyl etherified to afford an epoxy resin.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a curing agent for an epoxy resin, an epoxy resin and an epoxy resin composition which give a cured product having high adhesiveness and low water absorption.

[0002]

2. Description of the Related Art Heretofore, epoxy resin compositions containing an epoxy resin, a phenol novolac resin, and a curing accelerator as main components have been widely used in the field of encapsulating materials for electric / electronic parts and ICs. The high density and high integration of ICs in recent years have made it necessary for the sealing material to have high adhesiveness and low water absorption. In particular, the harsh condition of immersion in a solder bath in high-density mounting of ICs further increases the demand for cured products with high heat resistance, high adhesion, and low water absorption.

[0003]

However, in the conventional epoxy resin composition for encapsulant, the cresol novolac type epoxy resin generally used as an epoxy resin has high heat resistance, but it has high adhesiveness and water absorption. It has the disadvantage of being inferior in terms.

On the other hand, the phenol novolac resin, which is generally used as a curing agent, is still insufficient in terms of adhesiveness and water absorption rate, and satisfactory results are obtained under the above severer conditions. Absent.

[0005]

In view of these circumstances, the present inventors have earnestly studied for an epoxy resin composition that gives a cured product having excellent adhesiveness and low water absorption, and as a result,
An epoxy resin composition containing a modified phenol novolac resin having a specific molecular structure and an epoxy resin obtained by glycidyl etherification thereof is a cured product having high adhesiveness and low water absorption while maintaining heat resistance. The present invention has been completed by discovering that it indicates

That is, the present invention is based on the equation (1)

[0007]

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(In the formula, n represents an average and represents a positive number. R represents a hydrogen atom, a halogen atom, an alkyl group having 1 to 8 carbon atoms,
The individual R's representing any of the aryl groups may be the same or different from each other. ) A phenol novolak represented by the formula (2) obtained by addition-reacting dicyclopentadiene in the presence of an acid catalyst.

[0009]

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(Wherein R represents the same meaning as in formula (1), and P represents a hydrogen atom or --CH _2- ).

A modified phenol novolac resin having a bond represented by

(2) Epoxy resin obtained by glycidyl etherification of hydroxyl groups of the modified phenol novolac resin represented by the above formula (1), (3) (a) epoxy resin (b) modified phenol described in (1) above. An epoxy resin composition containing a novolac resin, (4) (a) an epoxy resin composition according to (2) above, and an epoxy resin composition containing a curing agent (b),

(5) (a) Epoxy resin described in (2) above. (B) Epoxy resin composition containing the modified phenol novolac resin described in (1) above. (6) Above containing a curing accelerator. (3), (4) or the epoxy resin composition according to (5), (7) the epoxy according to (3), (4), (5) or (6) above, containing an inorganic filler and a curing accelerator. A resin composition, (8) a cured product obtained by curing the epoxy resin composition according to the above (3), (4), (5), (6) or (7).

The modified phenol novolac resin in the present invention can be obtained by addition reaction of phenol novolacs with dicyclopentadiene in the presence of an acid catalyst. In this reaction, since the aromatic ring of the phenol novolac of the formula (1) is added to the double bond of dicyclopentadiene, the modified phenol novolac resin of the present invention is represented by, for example, the following formulas (A) to (C). Contains molecules.
The molecule represented by the formula (A) is an example of a molecule in which P is a hydrogen atom in the formula (2), and the formulas (B) and (C) are examples of a molecule in which P is —CH ₂ —. is there.

[0015]

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[0016]

[Chemical 6]

[0017]

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(R and n in formulas (A) to (C) have the same meanings as in formula (1), and m represents a positive number.)

The epoxy resin in the present invention can be obtained, for example, by reacting the above-mentioned modified phenol novolac resin with epihalohydrin in the presence of an alkali metal hydroxide.

The phenol novolaks represented by the formula (1) can be obtained by subjecting phenols and formalin to a condensation reaction in the presence of an acid catalyst. Equation (1)
Where n is a positive number and represents an average value, preferably n =
0.01-10, especially preferably n = 0.05-5.

The above-mentioned phenols include compounds having at least one phenolic hydroxyl group.
Specific examples of phenols that can be used include phenol,
Various o-, m-, p- of alkylphenols such as chlorophenol, bromophenol or cresol, ethylphenol, n-propylphenol, isobutylphenol, t-butylphenol, octylphenol, nonylphenol, xylenol, methylbutylphenol and di-t-butylphenol. Isomers or various o-, m-, p-isomers of vinylphenol, allylphenol, propenylphenol, ethynylphenol, or cycloalkylphenols such as cyclopentylphenol, cyclohexylphenol, cyclohexylcresol, or substituted phenols such as phenylphenol And halogen-substituted products thereof. These phenols may be used alone or in combination of two or more.

When carrying out the condensation reaction, any known method can be used. The amount of formalin used is usually 0.01 to 0.95 mol, preferably 0.1 to 0.9 mol, relative to 1 mol of phenols.

In the above condensation reaction, it is usually preferable to use an acid catalyst, and various acid catalysts can be used. Specific examples of usable acid catalysts include hydrochloric acid, sulfuric acid, p-toluenesulfonic acid, oxalic acid and the like. Examples thereof include inorganic or organic acids or Lewis acids such as boron trifluoride, anhydrous aluminum chloride and zinc chloride, and p-toluenesulfonic acid and oxalic acid are preferable. When using a gas such as hydrogen chloride that is in a gas state at room temperature, the reaction may be performed while blowing the gas into the reaction mixture. The amount of these acid catalysts used is not particularly limited, but is 0.001 to 0.1 mol per mol of the phenols.

The above condensation reaction can be carried out without solvent or in the presence of an organic solvent. Specific examples of the organic solvent that can be used include toluene, xylene, and methyl isobutyl ketone. The amount of the organic solvent used is usually 50 to 30 with respect to the total weight of the raw materials charged.
It is 0% by weight, preferably 100 to 250% by weight. The reaction temperature is usually in the range of 20 to 200 ° C.
0 ° C. is preferred. The reaction time is usually 1 to 30 hours, preferably 2 to 20 hours. Further, it is preferable to distill off the water generated during the reaction to the outside of the system in order to smoothly carry out the reaction.

After completion of the reaction, washing treatment is carried out until the pH of the washing liquid becomes 3 to 7, preferably 5 to 7. When performing a water washing treatment, sodium hydroxide, alkali metal hydroxides such as potassium hydroxide, calcium hydroxide, alkaline earth metal hydroxides such as magnesium hydroxide, ammonia, sodium dihydrogen phosphate and further diethylenetriamine,
The treatment may be carried out by using an organic amine such as triethylenetetramine, aniline or phenylenediamine, or a basic substance such as sodium oxalate as a neutralizing agent. The washing process may be performed according to a conventional method. For example, water in which the neutralizing agent is dissolved is added to the reaction mixture, and the separation and extraction operation is repeated.

After washing with water, unreacted phenols and solvent are distilled off under reduced pressure heating to concentrate the product,
It is possible to obtain the phenol novolaks represented by the formula (1). When R in the formula (1) is a halogen atom, the obtained phenol novolacs may be halogenated by a known method.

As the addition reaction of phenol novolacs to the double bond of dicyclopentadiene, conventionally known addition reaction of phenols to olefin can be applied. For example, a method of adding dicyclopentadiene to a phenol novolak in a heated and molten state in the presence of an acid catalyst can be mentioned.

The dicyclopentadiene used in the above addition reaction is usually in the proportion of 0.01 to 1 double bond of dicyclopentadiene to one aromatic ring to which a phenolic hydroxyl group is bonded in phenol novolacs. The amount used is preferably 0.05 to 0.95.

An acid catalyst is usually used in the above addition reaction. Although various kinds of acid catalysts can be used, boron trifluoride or a complex thereof with ethers, Lewis acids such as anhydrous aluminum chloride, zinc chloride, sulfuric acid and titanium chloride are preferable, and boron trifluoride or this is particularly preferable. And a complex of ethers and anhydrous aluminum chloride are preferred. The acid catalyst may be used alone or in combination of two or more kinds. The amount of the acid catalyst used is not particularly limited, but is usually 0.001 to 0.1 mol per equivalent of double bond of dicyclopentadiene. It is also possible to add these acid catalysts to the heated melt of the phenol novolacs in advance, or dilute them with an appropriate solvent, for example, a solvent inert to the reaction described below, and add them gradually.

Since many of the phenol novolacs used in this reaction are easily oxidized, it is preferable to purge the inside of the reaction vessel with nitrogen gas or the like during a series of reaction operations. Furthermore, this addition reaction is often accompanied by a large amount of heat, and the above acid catalyst is usually added to the heated melt or solvent melt of phenol novolacs in advance, and dicyclopentadiene is introduced into the reaction vessel while checking the reaction temperature. Preferably.

The addition reaction is usually 40 to 180 ° C., preferably 80 to 160 ° C., and the reaction time is usually 0.5 to 10 hours. Further, these reactions can be carried out in the presence of a solvent inert to the reaction such as nitrobenzene, diphenyl ether, dichlorobenzene and carbon disulfide. Further, the reaction product thus obtained is neutralized, or after repeatedly washing with water in the presence of a solvent, water is separated and drained, and then the solvent is removed under reduced pressure by heating to obtain the modified phenol novolac resin of the present invention. Obtainable.

As a method for obtaining the epoxy resin of the present invention from the modified phenol novolac resin of the present invention, a known method can be adopted. For example, to a dissolved mixture of the obtained modified phenol novolac resin and an excess of epichlorohydrin, epihalohydrin such as epibromhydrin, or while adding an alkali metal hydroxide such as sodium hydroxide or potassium hydroxide, 20 to 120 ° C. 1 to 1 at the temperature of
The epoxy resin of the present invention can be obtained by reacting for 0 hours.

In the reaction for obtaining the epoxy resin of the present invention, an aqueous solution of the alkali metal hydroxide may be used, in which case an aqueous solution of the alkali metal hydroxide is continuously added to the reaction mixture. Alternatively, water and epihalohydrin may be continuously distilled off under reduced pressure or atmospheric pressure, and liquid separation may be performed to remove water and epihalohydrin may be continuously returned to the reaction mixture.

Further, a quaternary ammonium salt such as tetramethylammonium chloride, tetramethylammonium bromide and trimethylbenzylammonium chloride is added as a catalyst to a dissolved mixture of phenol novolac and epihalohydrin, and the mixture is reacted at 50 to 150 ° C. for 1 to 5 hours. A solid or aqueous solution of an alkali metal hydroxide may be added to the halohydrin etherified product of the phenolic novolac obtained as described above, and the mixture may be reacted again at a temperature of 20 to 120 ° C. for 1 to 10 hours to dehydrohalogenate (ring closure). . In this case, the amount of the quaternary ammonium salt used is usually 1 to 10 g per 1 equivalent of the hydroxyl group of the phenol novolacs.
It is preferably 2 to 8 g.

The amount of epihalohydrin used in these reactions is usually 1 to 20 mol, preferably 2 to 10 mol, based on 1 equivalent of hydroxyl group of phenol novolacs. The amount of the alkali metal hydroxide used is 0.8 to 1.5 mol, preferably 0.9 to 1.1 mol, per equivalent of the hydroxyl group of the phenol novolak. Further, in order to allow the reaction to proceed smoothly, it is preferable to carry out the reaction by adding an aprotic polar solvent such as dimethyl sulfone or dimethyl sulfoxide in addition to alcohols such as methanol and ethanol.

When alcohols are used, the amount used is usually 2 to 20% by weight, preferably 4 to 15% by weight, based on the amount of epihalohydrin. When an aprotic polar solvent is used, it is usually 5 to 100% by weight, preferably 10 to 90% by weight, based on the amount of epihalohydrin.

After washing the reaction products of these epoxidation reactions with or without washing with water, under heating and reduced pressure, 110 to 250 ° C.
The epihalohydrin and the solvent are removed at a pressure of 10 mmHg or less. In order to further reduce the amount of hydrolyzable halogenated epoxy resin, the obtained epoxy resin is dissolved in a solvent such as toluene or methyl isobutyl ketone, and an aqueous solution of an alkali metal hydroxide such as sodium hydroxide or potassium hydroxide is used. In addition, further reactions can be performed to ensure ring closure. In this case, the amount of the alkali metal hydroxide used is usually 0.01 to 0.3 mol, preferably 0.05 to 0.2 mol, relative to 1 equivalent of the hydroxyl group of the phenol novolac used in the epoxidation. The reaction temperature is usually 50 to 120 ° C, and the reaction time is usually 0.5 to 2 hours.

After the completion of the reaction, the formed salt is removed by filtration, washing with water and the like, and the solvent such as toluene and methyl isobutyl ketone is distilled off under heating and reduced pressure to obtain the epoxy resin of the present invention.

The epoxy resin composition of the present invention can be obtained by using the epoxy resin of the present invention and / or the modified phenol novolac resin of the present invention as an essential component, and further adding a curing accelerator and the like if necessary. (3),
In the epoxy resin composition of the present invention described in (5), (6) and (7), the modified phenol novolac resin of the present invention can be used alone or in combination with other curing agents. When used in combination, the proportion of the modified phenol novolac resin of the present invention in the total curing agent is preferably 30% by weight or more, and particularly preferably 40% by weight or more. Specific examples of the curing agent that can be used in combination with the modified phenol novolac resin of the present invention include amine compounds such as diaminodiphenylmethane, diethylenetriamine, triethylenetetramine, diaminodiphenylsulfone, isophoronediamine and dicyandiamide, dimers of linolenic acid and ethylenediamine. Polyamide resin synthesized from and phthalic anhydride, trimellitic anhydride, pyromellitic anhydride, maleic anhydride, tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, methylnadic acid anhydride, hexahydrophthalic anhydride, methylhexahydro Phthalic anhydride, pheno
Examples thereof include novolak resins such as lunovolac and cresol novolac and modified products thereof, imidazole, BF ₃ -amine complex, and guanidine derivative. These curing agents may be used alone or in combination of two or more.

In the epoxy resin composition of the present invention described in (4), (5), (6) and (7), the epoxy resin of the present invention is used alone or in combination with other epoxy resins. You can When used in combination, the proportion of the epoxy resin of the present invention in the total epoxy resin is preferably 30% by weight or more, and particularly preferably 40% by weight or more. In this case, the epoxy resin used is not particularly limited as long as it is a compound having two or more epoxy groups in one molecule and is generally used for electronic devices. Specific examples of epoxy resins that can be used in combination include phenol novolac type epoxy resins, cresol novolac type epoxy resins, naphthol novolac type epoxy resins and other novolac type epoxy resins, bisphenol A type epoxy resins, bisphenol F type epoxy resins, bisphenol AD type resins. Epoxy resins obtained from aromatic dihydric phenols such as epoxy resins, bisphenol S type epoxy resins, bisphenol I type epoxy resins, biphenyl type epoxy resins, etc. Obtained by reacting polybasic acids such as phthalic acid and dimer acid with epihalohydrin Examples include glycidyl ester type epoxy resins, glycidyl amine type epoxy resins obtained by reacting polyamines such as diaminodiphenylmethane and isocyanuric acid with epihalohydrin. That. These epoxy resins may be used alone or in combination of two or more.

In the epoxy resin composition described in (3), (6) and (7), examples of the epoxy resin include the epoxy resins of the present invention and the other epoxy resins described above. In the epoxy resin composition described in (4), (6) and (7), examples of the curing agent include the above-mentioned other curing agents in addition to the modified phenol novolac resin of the present invention.

The amount of the curing agent used in the epoxy resin composition of the present invention is preferably 0.7 to 1.2 equivalents relative to 1 equivalent of epoxy groups of the epoxy resin. If the amount is less than 0.7 equivalent or more than 1.2 equivalent to 1 equivalent of the epoxy group, the curing may be incomplete and good cured physical properties may not be obtained.

A curing accelerator may be added to the epoxy resin composition of the present invention. Specific examples of the curing accelerator that can be used include imidazoles such as 2-methylimidazole, 2-ethylimidazole and 2-ethyl-4-methylimidazole, 2- (dimethylaminomethyl) phenol, 1,8-diaza-. Examples thereof include tertiary amines such as bicyclo (5,4,0) undecene-7, phosphines such as triphenylphosphine, and metal compounds such as tin octylate. The curing accelerator is epoxy resin 100
If necessary, 0.1 to 5.0 parts by weight is used with respect to parts by weight.

Further, the epoxy resin composition of the present invention is
It contains an inorganic filler as needed. Specific examples of the inorganic filler that can be used include silica, alumina, and talc. The proportion of the inorganic filler in the epoxy resin of the present invention is usually 0 to 90% by weight. Furthermore, various compounding agents such as a silane coupling agent, a release agent, and a pigment can be added to the epoxy resin composition of the present invention, if necessary.

The epoxy resin composition of the present invention can be obtained by uniformly mixing the above-mentioned components in a predetermined ratio.
The epoxy resin composition of the present invention can be easily made into a cured product by a method similar to a conventionally known method. For example, an epoxy resin and a curing agent, if necessary an inorganic filler, a curing accelerator and other compounding agents, if necessary, an extruder,
An epoxy resin composition is obtained by sufficiently mixing with a kneader, a roll or the like until it becomes uniform, and the epoxy resin composition is melted and then molded using a casting or transfer molding machine, The cured product can be obtained by heating at 80 to 200 ° C. for 2 to 10 hours.

Further, the epoxy resin composition of the present invention is dissolved in a solvent such as toluene, xylene, acetone, methyl ethyl ketone, methyl isobutyl ketone and the like to prepare glass fiber, carbon fiber, polyester fiber, polyamide fiber, alumina fiber, paper and the like. A prepreg obtained by impregnating a base material with heating and drying can be hot-press molded to obtain a cured product. In this case, the solvent is usually 10 to 10 in the mixture of the epoxy resin composition of the present invention and the solvent.
It is used in an amount of 70% by weight, preferably 15 to 65% by weight.

[0047]

EXAMPLES The present invention will now be described more specifically with reference to examples and comparative examples. In the following, parts are by weight unless otherwise specified.

Example 1 A flask equipped with a thermometer, a dropping funnel, a cooling tube, a fractionating tube, and a stirrer was charged with the following formula (3).

[0049]

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(In the formula, n is 0.91 (average value).)
Phenol novolac 2 with a softening point of 46.0 ° C
Charge 00 parts and blow 120 in an oil bath while blowing nitrogen.
The temperature was raised to ° C and the mixture was stirred. Then, 1 part of boron trifluoride diethyl ether complex was added, and 66 parts of dicyclopentadiene was added dropwise over 90 minutes. Then another 12
The reaction was performed at 0 ° C. for 3 hours. After completion of the reaction, 500 parts of methyl isobutyl ketone was added and completely dissolved, 20 parts by weight of sodium dihydrogen phosphate aqueous solution of 20 parts was added for neutralization, and further washing with water was repeated several times, and then the solvent was removed from the organic layer. Removed by heating under reduced pressure, and the following formula (4) in the molecule

[0051]

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(In the formula, P represents a hydrogen atom or --CH _2- )

247 parts of the modified phenol novolac resin (A) of the present invention having a bond represented by The softening point of the obtained modified phenol novolac resin is 94.7 ° C,
The hydroxyl equivalent was 133 g / eq.

Example 2 Compound 133 obtained by the above reaction while purging a flask equipped with a thermometer, a condenser and a stirrer with nitrogen gas
Parts, 370 parts of epichlorohydrin, and 26 parts of methanol were charged and dissolved. Further, the mixture was heated to 70 ° C., and 40.4 parts of flaky sodium hydroxide (99% pure content) was refluxed under reflux.
The mixture was added in portions over a period of time, and then the mixture was further reacted at 70 ° C. for 70 minutes. After completion of the reaction, 150 parts of warm water was added and washed with water, the oil layer was concentrated at 130 ° C. under reduced pressure to distill away epichlorohydrin, and 380 parts of methyl isobutyl ketone was added to the residue to dissolve it.

Further, this methyl isobutyl ketone solution is heated to 70 ° C. and a 30% by weight aqueous sodium hydroxide solution 1 is added.
After adding 0 part and reacting for 1 hour, washing with water was repeated 3 times to make the pH of the washing solution neutral. Further, the aqueous layer was separated and removed, and methyl isobutyl ketone was distilled off from the oil layer under heating and reduced pressure using a rotary evaporator to obtain 176 parts of the epoxy resin (B) of the present invention. The obtained epoxy resin had a softening point of 73.5 ° C. and an epoxy equivalent of 209 g / eq.

Examples 3 to 5 and Comparative Example 1 As Example 3, the epoxy resin was added to the o-cresol novolac type epoxy resin EOCN1020 (epoxy equivalent 20).
0 g / eq, manufactured by Nippon Kayaku Co., Ltd., a modified phenol novolac resin (A) as a curing agent, an epoxy resin (B) as an epoxy resin in Example 4, and a phenol novolac (a hydroxyl equivalent of 106 g / a) as a curing agent. eq, softening point 83 ° C,
Manufactured by Nippon Kayaku Co., Ltd., epoxy resin (B) as an epoxy resin as Example 5, modified phenol novolac resin (A) as a curing agent, and EOCN1020 as an epoxy resin and a curing agent as Comparative Example 1. Triphenylphosphine (TP) as a curing accelerator
P) and compounded in the composition shown in the column of composition of Table 1 and kneaded with a roll at 70 ° C. for 15 minutes to obtain an epoxy resin composition, which is 150 ° C. and molding pressure 50 kg.
/ Cm ² in to 180 seconds transfer molding, 2 hours then 160 ° C., further create a 8 hours curing allowed test piece at 180 ° C., was measured glass transition point, peel strength, water absorption. The results are shown in Table 1. The conditions for measuring the glass transition point, peel strength, and water absorption are as follows. Also, in the table, the numerical values in the column of the composition of the blend indicate parts by weight.

Glass transition temperature thermomechanical measuring device (TMA): manufactured by Vacuum Riko Co., Ltd. TM-
7000 Temperature rising rate: 2 ° C / min Water absorption rate Test piece (cured product): Diameter 50 mm Thickness 3 mm Disk Weight increase rate (%) after boiling in 100 ° C water for 20 hours Peel strength Peel strength 35 μm thick copper foil The epoxy resin composition was poured into a shiitake mold and this was heated at 160 ° C for 2 hours + 180 ° C for 8 hours.
Maximum value of strength when a copper foil of a cured product obtained by time curing is pulled at a constant rate in the direction of 180 ° C. Tensile tester: Orientec Tensilon Tension rate: 200 mm / min

[0058]

[Table 1] Table 1 Actual Example Comparative Example 3 4 5 1 Composition of composition EOCN1020 100 100 Modified phenol novolac resin (A) 67 Epoxy resin (B) 100 100 Phenol novolac 51 64 53 TPP 1 1 1 1 1 Cured product Physical properties Glass transition point (℃) 155 156 158 154 Peel strength (kg / cm) 2.81 2.93 3.01 2.61 Water absorption rate (%) 1.09 0.98 0.89 1.27

As shown in Table 1, the cured products of the modified phenol novolac resin and epoxy resin of the present invention showed high adhesiveness and low water absorption while maintaining a high glass transition point.

[0060]

The modified phenol novolac resin or epoxy resin of the present invention can give a cured product having excellent adhesiveness and water resistance, and can be used as a molding material, casting material,
It is extremely useful for a wide range of applications such as laminated materials, paints, adhesives and resists.

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Claims (8)

[Claims] (1) Formula (1) (In the formula, n is a positive number and represents an average value. R is a hydrogen atom,
Each R represents a halogen atom, an alkyl group having 1 to 8 carbon atoms or an aryl group, and each R may be the same or different. ) A phenol novolac represented by the formula (2) embedded image obtained by addition reaction of diphenol pentadiene in the presence of an acid catalyst. (In the formula, R represents the same meaning as in formula (1), P represents a hydrogen atom or —CH ₂ —) and a modified phenol novolac resin having a bond in the molecule. 2. An epoxy resin obtained by glycidyl etherification of the hydroxyl groups of the modified phenol novolac resin according to claim 1. 3. An epoxy resin composition comprising (a) an epoxy resin and (b) the modified phenol novolac resin according to claim 1. 4. An epoxy resin composition comprising (a) the epoxy resin according to claim 2 and (b) a curing agent. 5. An epoxy resin composition comprising (a) the epoxy resin according to claim 2 and (b) the modified phenol novolac resin according to claim 1. 6. The epoxy resin composition according to claim 3, 4 or 5 containing a curing accelerator. 7. The epoxy resin composition according to claim 3, which contains an inorganic filler. 8. A cured product obtained by curing the epoxy resin composition according to claim 3, 4, 5, 6 or 7.