JPH04275317A - New novolak type resin and its production - Google Patents

Abstract

PURPOSE:To obtain the subject resin, containing a specific amount of a compound having a specified structure, excellent in resistance to moisture and heat and operating efficiency, etc., and useful as an epoxy resin for electrical and electronic materials such as sealing media by reacting a dimethylol compound with naphthols. CONSTITUTION:One mol compound (e.g. 4,6-dimethylol-2-methylphenol) expressed by formula I (R2 is 1-4C alkyl; R3 and R4 are H or 1-4C alkyl) and preferably 3.5-6mol compound (e.g. 1-naphthol) expressed by formula II (R1 is H or 1-4C alkyl) are subjected to dehydrating condensation reaction in the presence of an acid catalyst such as hydrochloric acid in an amount of preferably 0.1-30wt.% (based on the compound expressed by formula I) in water, etc., to provide the objective resin expressed by formula III [(n) is 0-6]. The compound expressed by formula III [(n) is 0] in an amount of >=30% is contained in the resin expressed by formula III. The aforementioned resin expressed by formula III is then reacted with an epihalohydrin in the presence of dimethyl sulfoxide to afford a resin, expressed by formula IV and containing >=30% compound expressed by formula III [(n) is 0].

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention is a novel method for producing novolak-type resins and epoxy resins, which provides cured products with excellent moisture resistance and heat resistance, and has low viscosity, which is extremely advantageous in terms of workability. Regarding.

0002

[Prior art] Generally, epoxy resin has adhesive properties, heat resistance,
Because of its excellent electrical and mechanical properties, it is widely used as a material for electrical and electronic components such as adhesives, paints, electrical insulation materials, sealants, and various composite materials.

Among them, cresol novolac type epoxy resins are widely used, especially as materials for electrical and electronic parts such as sealants, because of their well-balanced properties such as heat resistance of the cured products.

[0004] However, in recent years, when mounting an IC using the surface mounting method, the IC package is directly immersed in a solder bath, which exposes it to severe temperature conditions. As a result, the problem of cracks occurring in the IC package has arisen, and a cured epoxy resin is required to have heat resistance and low water absorption.

[0005]

[Problems to be Solved by the Invention] In order to achieve these heat resistance and low water absorption properties at the same time, various studies have been made, and a naphthol novolac type epoxy resin has been proposed in Japanese Patent Publication No. 62-20206. It is disadvantageous in terms of workability, especially in terms of viscosity, and in terms of moldability when actually making packages.

[0006] The present invention provides a novel novolac type resin which is excellent in terms of heat resistance, low water absorption, and workability, and a method for producing it.

[0008]

[Means for Solving the Problems] As a result of intensive studies to solve these problems, the present inventors have found that these problems can be solved by creating a specific structure when introducing naphthol. This finding led to the completion of the present invention.

That is, the present invention provides formula (1) (A)

0
010]

[C5]

(In the formula, R2 is an alkyl group having 1 to 4 carbon atoms, R1, R3 and R4 are each independently a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and n is a value of 0 to 6. Novolac type resin represented by (respectively shown),

0
(2) Formula (B)

[0013]

[C6]

A dimethylol compound represented by (wherein R2 represents an alkyl group having 1 to 4 carbon atoms, and R3 and R4 each independently represent a hydrogen atom or an alkyl group having 1 to 4 carbon atoms) Formula (C)

[0015]

[C7]

(In the formula, R1 is a hydrogen atom or a carbon number of 1 to
4 shows the alkyl group. ) A novolak type resin containing 30% by weight or more of a compound where n=0 in the above formula (A).

(3) Formula (D)

[0018]

[Chemical formula 8]

(In the formula, R2 is an alkyl group having 1 to 4 carbon atoms, R1, R3 and R4 are each independently a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and n is a value of 0 to 6. epoxy resin represented by (respectively shown),

002
(4) An epoxy resin obtained by reacting the novolac type resin described in (2) above with epihalohydrin and containing 30% by weight or more of a compound where n=0 in the above formula (D),

(5) The above (3) characterized in that the novolac type resin described in the above (1) or (2) is reacted with epihalohydrin in the presence of dimethyl sulfoxide.
) or the method for producing the epoxy resin described in (4) above.

The epoxy resin of the present invention has reduced hydrolyzable chlorine, which is a requirement in terms of reliability, and can provide a cured product with heat resistance and low water absorption, and is easy to work with. It is also extremely advantageous in terms of.

The present invention will be explained in detail below. Formula (A)
The novolac type resin (A) can be produced by reacting (dehydration condensation) a dimethylol compound (B) of formula (B) and a naphthol (C) of formula (C) in the presence of an acid catalyst. Can be done.

Specific examples of the dimethylol compound (B) include 4,6-dimethylol-2-methylphenol, 4,
, 6-dimethylol-2,3,5-trimethylphenol, 4,6-dimethylol-2-t-butylphenol, 4,6-dimethylol-2-t-butyl-5-methylphenol, 4,6-dimethylol-2 , 3-dimethylphenol, 4,6-dimethylol-2,5-dimethylphenol, and the like.

Specific examples of naphthols (C) include 1
-naphthol, 2-naphthol, 1-methyl-2-naphthol, 2-methyl-1-naphthol, and the like. Specific examples of acid catalysts include hydrochloric acid, sulfuric acid, phosphoric acid, p-
Toluenesulfonic acid, oxalic acid, etc. can be used.

It is preferable to use 2 to 8 moles of naphthols (C) per mole of dimethylol compound (B),
It is particularly preferable to use 3.5 to 6 mol. The acid catalyst is preferably used in an amount of 0.1 to 30% by weight of the dimethylol compound (B).

The reaction may be carried out in the presence of water, or
Alcohols and ketones such as acetone may be used as the solvent. A reaction temperature of 40 to 85°C is sufficient, and
The reaction time may be 1 to 10 hours.

After the reaction is completed, the acid catalyst used is neutralized or washed with water to return it to neutrality, and unreacted naphthol is removed by heating distillation under reduced pressure.

In this way, novolac type resin (A)
However, considering the viscosity in terms of workability, the above (
As described in 2), in the reaction product of dimethylol compound (B) and naphthols (C), n=0 in formula (A)
The content of the compound is preferably 30% by weight or more, particularly preferably 35% by weight or more.

[0030] Such a novolak type resin according to the above (2), in which the content of the compound where n=0 in formula (A) is 30% by weight or more, is obtained by controlling the reaction temperature to 40 to 85% by weight as described above.
℃, and removing unreacted naphthol by heating distillation under reduced pressure.

[0031] From the viewpoint of the heat resistance of the cured epoxy resin obtained by further epoxidation, or the heat resistance of the cured product when used as a curing agent, the novolak type resin described in (2) above is used. Formula (E) contained in

[0032]

[Chemical formula 9]

(wherein R2, R3, and R4 have the same meanings as above), substituted phenols, naphthols, etc. having a molecular weight lower than that of the compound where n=0 in formula (A) The total content of compounds having phenolic hydroxyl groups is preferably 10% by weight or less, particularly 7% by weight or less.
It is preferably less than % by weight.

The above-mentioned (1) or (
The epoxy resin described in (3) or (4) above can be obtained by reacting the novolac type resin described in 2) with epihalohydrin. At this time, by performing the reaction in the presence of dimethyl sulfoxide, the resulting epoxy resin has significantly reduced hydrolyzable chlorine and can achieve improved reliability.

Specific examples of epihalohydrin include epichlorohydrin and epibromohydrin, and epichlorohydrin is preferably used industrially.

The reaction is carried out by combining the novolac type resin described in (1) or (2) above with epihalohydrin as it is or by adding dimethyl sulfoxide, and adding a quaternary ammonium salt such as tetramethylammonium chloride or tetramethylammonium bromide or water. The reaction is carried out in the presence of an alkali metal hydroxide such as sodium oxide or potassium hydroxide, and when a quaternary ammonium salt is used, the reaction stops at the ring-opening addition reaction stage, so the above alkali metal hydroxide is then reacted. is added to cause a ring-closing reaction. In addition, when adding an alkali metal hydroxide to the reaction from the beginning,
A ring-opening addition reaction and a ring-closing reaction are performed at once.

Epihalohydrin is usually used in an amount of 1 to 50 mol, preferably 3 to 1 mol of hydroxyl group in the novolak resin.
It is used in a range of 15 moles. In addition, when dimethyl sulfoxide is used, the amount used is 10% of the novolac type resin.
It is preferably 20 parts by weight to 200 parts by weight relative to 0 parts by weight.

The amount of alkali metal hydroxide used is preferably 0.8 to 1 mole of hydroxyl group in the novolak resin.
1.5 mol, particularly preferably in the range of 0.9 to 1.3 mol, and when a quaternary ammonium salt is used, the amount used is usually 0 to 1 mol of hydroxyl group of the novolac type resin.
．． The amount ranges from 0.001 to 1 mol, preferably from 0.005 to 0.5 mol.

The reaction temperature is usually 30 to 130°C, preferably 30 to 100°C. Moreover, the reaction can also be allowed to proceed while removing water produced in the reaction from the reaction system.

After completion of the reaction, the by-produced salt or dimethyl sulfoxide is removed by washing with water or the like, and excess epihalohydrin is distilled off to obtain the epoxy resin described in (3) or (4) above.

Further, in order to further remove impurities, the obtained epoxy resin may be further subjected to the following treatment. That is, an epoxy resin is dissolved in a solvent such as methyl isobutyl ketone, and reacted in the presence of an alkali metal hydroxide such as sodium hydroxide at 50 to 100°C for 0.5 to 3 hours, and after the reaction is completed, washing with water is repeated. , return the aqueous phase to neutrality,
The epoxy resin described in (3) or (4) above can be obtained by distilling off a solvent such as methyl isobutyl ketone under reduced pressure, and by further providing such a treatment step, a higher purity epoxy resin can be obtained. is obtained.

At this time, the amount of the alkali metal hydroxide such as sodium hydroxide used is preferably in the range of 0.01 to 0.2 mol per 1 mol of hydroxyl group of the novolak resin.

In this way, the epoxy resin (D) is obtained, but considering the viscosity in terms of workability, the above (4)
As described in , in the reaction product of a novolac type resin and epihalohydrin, the content of the compound of formula (D) where n = 0 is preferably 30% by weight or more, particularly preferably 35% by weight or more. .

The epoxy resin described in (4) above, in which the content of the compound where n=0 in formula (D) is 30% by weight or more, uses the novolac type resin described in (2) above as a raw material. This can be obtained by

In addition, from the viewpoint of heat resistance of the cured product, the above (4)
Formula (F) contained in the epoxy resin described in )

[0046]

[Chemical formula 10]

(In the formula, R2, R3, R4 have the same meanings as above), substituted phenols, glycidylated naphthols, etc., of the formula (D)
The total amount of compounds with lower molecular weight than the compound with n=0 is 10
It is preferably at most 7% by weight, particularly preferably at most 7% by weight.

The epoxy resin of the present invention can be used alone or in combination with other epoxy resins, and can be used in the same way as ordinary epoxy resins.
Polyamine-based cured products such as aliphatic polyamines, aromatic polyamines, and polyamide polyamines; acid anhydride-based curing agents such as hexahydrophthalic anhydride and methyltetrahydrophthalic anhydride; phenol-based curing agents such as phenol novolak and cresol novolac; It can be hardened using a Lewis acid such as boron fluoride or a salt thereof, a hardening agent such as dicyandiamide, or the like. Moreover, various compounding agents such as a curing accelerator and an inorganic or organic filler can be added as necessary.

The novolac type resin of the present invention can be used as a curing agent for the epoxy resin of the present invention, and can also be used as a curing agent for other known epoxy resins.

The epoxy resin or novolak type resin of the present invention provides a cured product with excellent heat resistance and low water absorption, and therefore can be used in a wide range of fields where these properties are required. Specifically, insulating materials, laminates, sealing materials, molding materials, composite materials, etc. can be exemplified.

The novolac type resin and epoxy resin of the present invention have low melt viscosity and are therefore excellent in workability. In particular, since it has an alkyl group (R2) at the o-position of the benzene nucleus, it has a great advantage of having a lower melt viscosity than those having no alkyl group at the o-position.

[0052]

[Examples] The present invention will be explained below with reference to Examples. Example 1 (Novolac type resin synthesis step) 108 g (1 mol) of orthocresol is charged into a glass container equipped with a thermometer, a stirrer, and a cooling tube, and dissolved while maintaining the temperature at 30 to 35°C.

After dissolution, 30% sodium hydroxide aqueous solution 1
34 g (1 mol as sodium hydroxide) was added dropwise while being careful not to generate heat. During this time, the reaction temperature was maintained at 30°C. Thereafter, the reaction was continued for 1 hour while maintaining the reaction temperature.

Next, 60 g (2
mol) was added thereto, and the mixture was reacted for 1 hour at a reaction temperature of 30°C and further for 2 hours at a reaction temperature of 45°C.

Next, the reaction solution was cooled to 20°C to 25°C, and 91.3 g of concentrated hydrochloric acid (0.95 mol as pure hydrochloric acid) was added.
was added dropwise, being careful not to generate heat. 250 ml of methanol and 576 g (4 mol) of 1-naphthol were added to the reaction solution containing the dimethylolated product of orthocresol (4,6-dimethylol-2-methylphenol) thus obtained.

Then, the reaction temperature was raised to 50° C., and 10 g of concentrated hydrochloric acid (0.1 mol as pure hydrochloric acid) was immediately added dropwise. After the dropwise addition, the reaction temperature was maintained at 60° C. for 2 hours, and the mixture was further heated to 80° C. and reacted for 1 hour.

After the reaction was completed, in order to remove the acid catalyst, it was dissolved in 1000 ml of methyl isobutyl ketone and washed with water repeatedly. The methyl isobutyl ketone phase, which has been returned to neutrality by repeated washing with water, is heated and distilled under reduced pressure to distill off methyl isobutyl ketone and unreacted 1-naphthol. R2 = CH3, R1
=H, R3 =H, R4 =H, average value of n is 3.8
] 400g was obtained.

Softening temperature (JI) of the obtained resin (A-1)
S K2425 ring and ball method) at 104°C, hydroxyl equivalent (
g/mol) was 141. In addition, we performed GPC analysis,
In formula (A) determined from the retention time of standard polystyrene, n=
0 component was separated, and a mass spectrum (
FAB-MS).

As a result, M+ 420 was obtained, so this component can be expressed as R2 = CH3, R1 =
It was confirmed that the components were H, R3 = H, R4 = H, and n = 0. Also, from the GPC peak, the content of this component in the resin (A-1) was 53% by weight, and the total amount of components with lower molecular weight than this component was 5% by weight, and gas chromatography showed that 1- The amount of naphthol was found to be less than 1% by weight.

(Epoxy resin synthesis step) 141 g of the resin (A-1) obtained in the novolak type resin synthesis step, 460 g of epichlorohydrin, and 230 g of dimethyl sulfoxide were charged into a 1 liter reactor equipped with a thermometer and a stirring device, and the atmosphere was replaced with nitrogen. After this, 40 g of sodium hydroxide was gradually added in a 30°C water bath.

[0061] At 30°C for 5 hours, being careful not to generate heat,
The reaction was carried out at 0°C for 2 hours and then at 70°C for 1 hour. Then, water was added to wash the aqueous phase until it became neutral. Thereafter, epichlorohydrin and dimethyl sulfoxide were removed from the oil layer under reduced pressure.

[0062] Then 400g of methyl isobutyl ketone
and redissolved. Add 20g of 20% sodium hydroxide solution to the obtained methyl isobutyl ketone solution and raise the reaction temperature to 7.
The reaction was carried out at 0°C for 2 hours. After the reaction, washing with water was repeated and methyl isobutyl ketone was removed from the methyl isobutyl ketone phase under reduced pressure to form a yellow solid (D-1) [in formula (D), R2 = CH3, R1 = H, R3 = H, R
4 = H, average value of n is 3.8] 167 g was obtained.

The product (D-
The softening temperature of 1) is 84℃ and the epoxy equivalent (g/mol)
was 212. In addition, GPC analysis was performed in the same manner as above, and a peak that seemed to be the component of n = 0 in formula (D) was fractionated, and when analyzed by mass spectrometry (FAB-MS), M+ 588 was obtained. Therefore, this component has the formula (D
), R2 = CH3, R1 = H, R3 = H, R4
It was confirmed that the component was =H and n=0.

[0064] Also, from the GPC peak, the content of this component in the product (D-1) was 45% by weight, and the total amount of components with lower molecular weight than this component was 4.5% by weight. . Also, the product (D-1) at 150°C with an ICI viscometer
The melt viscosity was 4 poise. Also, product (D-1)
The amount of hydrolyzable chlorine was measured and found to be 170 ppm.

[0065] In this example and the following examples, GPC analysis and measurement of the amount of hydrolyzable chlorine were carried out by the following method.

GPC analysis GPC device; Shimadzu (column; TSK-G-3000XL (1 piece) + TSK
-G-2000XL (2 bottles) Solvent: Tetrahydrofuran 1ml/min test
Out; UV

Amount of hydrolyzable chlorine: Dissolve the epoxy resin in dioxane, add a 1N KOH ethanol solution, boil under reflux for 30 minutes, and then quantify by potentiometric titration using a silver nitrate solution.

Example 2 (Novolac type resin synthesis step) Novolac type resin (A-2) [ In formula (A), R2 = CH3, R
1 = H, R3 = H, R4 = H, the average value of n is 3.
6] 405g was obtained.

The softening temperature of the resin (A-2) obtained was 98
℃, and the hydroxyl equivalent was 142. In addition, GPC analysis and mass spectrum (FAB-MS) were performed in the same manner as in Example 1, and the component of M+ 420 [R2 = CH3 in formula (A)]
, R1 = H, R3 = H, R4 = H, n = 0] in the resin (A-2) at a content of 61% by weight.

Further, the total amount of components having a lower molecular weight than this component was 5% by weight, and the amount of 1-naphthol was determined by gas chromatography to be 1% by weight or less.

(Epoxy resin synthesis step) In the epoxy resin synthesis step of Example 1, 141 g of product (A-1)
Product (D-2) [in formula (D), R
2 = CH3, R1 = H, R3 = H, R4 = H
, the average value of n was 3.6] 171 g was obtained. The softening temperature of the product (D-2), which is an epoxy resin, was 78°C and the epoxy equivalent was 213.

[0072] Also, by the same analysis as in Example 1, M+5
88 was obtained, and this component is represented by formula (D), R2 = CH3, R
It was confirmed that the components were 1 = H, R3 = H, R4 = H, and n = 0. The content of this component in the product (D-2) was 55% by weight, and the total amount of components with lower molecular weight than this component was 4.3% by weight. Further, the viscosity (150° C.) measured by an ICI viscometer was 3.2 poise, and the amount of hydrolyzable chlorine was 165 ppm.

Example 3 (Epoxy resin synthesis step) In the epoxy resin synthesis step of Example 1, the amount of dimethyl sulfoxide used was 70 g.
By the same operation except for
=H, R4 =H, average value of n is 3.8] 170 g was obtained. The product (D-3), which is an epoxy resin, had a softening temperature of 85°C and an epoxy equivalent of 215.

[0074] Also, by the same analysis as in Example 1, M+5
88 was obtained, and this component is represented by formula (D), R2 = CH3, R
It was confirmed that the components were 1 = H, R3 = H, R4 = H, and n = 0. The content of this component in the product (D-3) was 44% by weight, and the total amount of components with lower molecular weight than this component was 5% by weight. In addition, the viscosity (150°C) with an ICI viscometer is 4 poise, and the amount of hydrolyzable chlorine is 2.
It was 30 ppm.

Example 4 (Epoxy resin synthesis step) 141 g of the product (A-1) obtained in the novolac resin synthesis step of Example 1 and 460 g of epichlorohydrin were added to a thermometer, a stirring device, a dropping funnel, and a produced water separation device. After purging the 1-liter reactor with nitrogen, 85 g of a 48% aqueous sodium hydroxide solution was added dropwise over 5 hours.

During the dropping, the reaction temperature was 60°C and the pressure was 100~1
Under conditions of 50 mmHg, the produced water and the water in the aqueous sodium hydroxide solution were continuously removed from the reaction system by azeotroping with epichlorohydrin, and epichlorohydrin was returned to the system.

[0077] After recovering excess unreacted epichlorohydrin under reduced pressure, 500% of methyl isobutyl ketone was recovered.
ml and washed with 100 ml of water until the aqueous phase became neutral. Methyl isobutyl ketone was removed from the methyl isobutyl ketone phase under reduced pressure, and then 400 g of methyl isobutyl ketone was added again to dissolve it again.

2 to the obtained methyl isobutyl ketone solution.
Add 20g of 0% sodium hydroxide solution and reaction temperature: 70℃
It reacted for 2 hours. After the reaction was completed, washing was repeated with water until the aqueous phase became neutral.

Next, methyl isobutyl ketone was removed from the methyl isobutyl ketone phase under reduced pressure to obtain the product (D-4).
) [In formula (D), R2 = CH3, R1 = H,
R3 = H, R4 = H, average value of n is 3.8] 170
I got g. The product (D-4), which is an epoxy resin, had a softening temperature of 84°C and an epoxy equivalent of 217.

[0080] Also, by the same analysis as in Example 1, M+5
88 was obtained, and this component is represented by formula (D), R2 = CH3, R
It was confirmed that the components were 1 = H, R3 = H, R4 = H, and n = 0. The content of this component in the product (D-4) was 43% by weight, and the total amount of components with lower molecular weight than this component was 4% by weight. In addition, the viscosity (150°C) with an ICI viscometer is 4 poise, and the amount of hydrolyzable chlorine is 5.
It was 30 ppm.

Application Examples and Comparative Examples Application Examples 1 to 4 Phenol novolac (Nippon Kayaku (Nippon Kayaku)
Co., Ltd., softening temperature 85°C, hydroxyl equivalent (g/mol) 1
05), a composition obtained by blending the epoxy resins (D-1) to (D-4) of the present invention obtained in Examples 1 to 4 and triphenylphosphine (TPP) as a curing accelerator.
Roll kneading was carried out at ~80°C for 15 minutes, then cooled, pulverized, and formed into a doublet. After molding using a transfer molding machine, precuring was carried out at 160°C for 2 hours, and post-curing was performed at 180°C for 8 hours to obtain a cured product ( A test piece) was obtained.

Comparative Example 1 As Comparative Example 1, a cresol novolak type epoxy resin containing no naphthalene core (manufactured by Nippon Kayaku Co., Ltd.; EOCN-1020, softening temperature 70°C, epoxy equivalent (g /mol) 200), phenol novolak and triphenylphosphine (TPP) similar to the application example.
) was blended and heated and cured in the same manner as in Application Examples 1 to 4 to prepare test pieces.

The glass transition temperature (T
g) The water absorption rate was measured and an adhesion test was performed. The conditions for measuring the glass transition temperature and water absorption, and the conditions for conducting the adhesion test are as follows.

Glass transition temperature thermomechanical measuring device (TMA); manufactured by Shinku Riko Co., Ltd. TM
-7000 Temperature increase rate: 2°C/min

Water absorption test piece Diameter: 50 mm, thickness: 3 mm, disk condition Water absorption rate (weight %) based on weight increase after boiling in water at 100°C for 50 hours

Adhesion Test Adhesive strength was evaluated by tensile shear according to ASTM D1002. The following criteria were used as a guideline for adhesion.

[0087]

[0088]

[Effects of the Invention] The novolac type resin and epoxy resin of the present invention not only have a low melt viscosity and are good in terms of workability, but also the cured products obtained using the resin of the present invention have high heat resistance and It is a resin with great industrial value as it has low water absorption and satisfies strict requirements for heat resistance and moisture resistance. or,
According to the production method of the present invention, an epoxy resin with a small amount of hydrolyzable chlorine can be obtained.

Claims (5)

[Claims] Claim 1: Formula (A) [Formula 1] (wherein, R2 is an alkyl group having 1 to 4 carbon atoms, R1
, R3 and R4 each independently represent a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and n represents a value of 0 to 6. ) Novolac type resin. Claim 2: Formula (B) [Formula 2] (wherein, R2 is an alkyl group having 1 to 4 carbon atoms, R3
and R4 are each independently a hydrogen atom or a carbon number of 1 to
4 alkyl groups are shown respectively. ) and a naphthol compound represented by formula (C) (wherein R1 represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms). , the compound of formula (A) of claim 1 where n=0 is 3
Novolak type resin containing 0% by weight or more. Claim 3: Formula (D) [Image Omitted] (wherein, R2 is an alkyl group having 1 to 4 carbon atoms, R1
, R3 and R4 each independently represent a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and n represents a value of 0 to 6. ) Epoxy resin. 4. A compound obtained by reacting the novolak type resin according to claim 2 with epihalohydrin, and having the formula (D) according to claim 3.
An epoxy resin containing 30% by weight or more of a compound where n=0. 5. The method for producing an epoxy resin according to claim 3 or 4, characterized in that the novolak type resin according to claim 1 or 2 and epihalohydrin are reacted in the presence of dimethyl sulfoxide.