JPH0764911B2 - Method for producing high molecular weight epoxy resin - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a high molecular weight epoxy resin used for adhesives, insulating materials, paints, molded products, films and the like.

(Prior Art) A method for producing a high molecular weight epoxy resin using a relatively low molecular weight difunctional epoxy resin and a bifunctional phenol as a raw material is generally called a two-step method. No. 2,615,008 and Japanese Patent Publication No. 28494/28. According to the description in this publication, a high molecular weight epoxy resin having an epoxy equivalent of 5,600 is obtained by reacting at 150 to 200 ° C. in the absence of solvent using sodium hydroxide as a polymerization catalyst. The average molecular weight of this resin can be estimated to be about 11,000. There is no example using a solvent in these documents.

Documents describing the use of a solvent include U.S. Pat.No. 3,306,872, JP-A-54-52200, JP-A-60-118757, JP-A-60-144323, and There is a bulletin such as Kaisho 60-144324. The solvents described in these publications are methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, ethylene glycol monoethyl ether, ethylene glycol monomethyl ether, and the like. These solvents are classified into ketone type and ether type (cellosolve type) solvents.

According to US Pat. No. 3,306,872, either methyl ethyl ketone or ethylene glycol monomethyl ether is used as a solvent, and the solid content concentration of the solution is 20 to
60%. As a catalyst, a hydroxide or phenolate of alkali metal or benzyltrimethylammonium is used. The polymerization reaction temperature is set to 75 to 150 ° C, and the weight average molecular weight of the produced high molecular weight epoxy resin is at least
The reaction continues until it reaches 40,000 or more. The average molecular weight is determined by the viscosity method and measured as 50,000 to 1,000,000. However, it is known that the calculated value of the viscosity method greatly depends on the setting of parameters used for calculation. Therefore, it cannot be said that the method for measuring molecular weight is accurate.

An example in which a high molecular weight epoxy resin is considered to be obtained by polymerizing in a solvent is described in JP-A-
In 54-52200, using ethylene glycol monoethyl ether as a solvent, a high-molecular-weight epoxy resin having an average molecular weight of 45,500 was obtained, and in JP-A-60-118757, methyl isobutyl ketone, cyclohexanone was used as a solvent. With ethylene glycol monoethyl ether,
It was found that a high molecular weight epoxy resin having an average molecular weight of up to 31,000 was obtained, and JP-A-60-1443223 discloses that methyl ethyl ketone was used as a solvent to obtain a high molecular weight epoxy resin having an average molecular weight of 53,200. In the 60-144324 publication,
Using methyl ethyl ketone as a solvent, the average molecular weight is 66,000
It is described that a high molecular weight epoxy resin of
In each of the above-mentioned four publications, the average molecular weight is measured by gel permeation chromatography, but the measurement conditions and calculation method are not described. The molecular weight obtained by gel permeation chromatography varies greatly depending on the measurement conditions such as the type of filler used and the type of eluent and the calculation method, and it is difficult to obtain an accurate value.

In any of the above-mentioned documents, there is no description to the effect that the obtained high molecular weight epoxy resin film is formed. Further, since the obtained epoxy resin is dissolved in a solvent other than an amide-based solvent, the so-called high molecular weight polymerized linearly to have a film forming ability of sufficient strength by the methods described in these documents. It is clear that no epoxy resin has been obtained.

A problem with the conventional technique is that the polymerization reaction time becomes considerably long when a general polymerization reaction solvent is used in producing a high molecular weight epoxy resin. Even in the examples of the aforementioned patents, the reaction time when using a ketone-based or ether-based solvent is often 10 to 24 hours, and the polymerization reaction time when a solvent is not used during the polymerization reaction is 1.5 to 10 hours. It is significantly longer than

(Problems to be Solved by the Invention) The present invention compares an ultra-high molecular weight epoxy resin linearly polymerized to have a film forming ability with sufficient strength, which was not obtained by the conventional method, with a conventional method. It is an object of the present invention to provide a method which can be manufactured in a remarkably short time.

(Means for Solving the Problem) The method for producing a high molecular weight epoxy resin of the present invention is a method of producing a high molecular weight epoxy resin by heating a bifunctional epoxy resin and a bifunctional phenol in a polymerization reaction solvent in the presence of a catalyst for polymerization. In the method for producing a resin, the compounding equivalent ratio of a bifunctional epoxy resin and a bifunctional phenol is set to epoxy group / phenolic hydroxyl group = 1: 0.9 to 1.0, and lithium hydride, sodium hydride, in an amide solvent, One or more kinds of catalysts selected from lithium borohydride and sodium borohydride catalysts are used, and the solid content concentration during the polymerization reaction is set to 30% or less for the polymerization.

Hereinafter, the present invention will be described in detail.

The bifunctional epoxy resin in the present invention may be any compound as long as it is a compound having two epoxy groups in the molecule, for example, bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, Alicyclic epoxy resins, aliphatic chain epoxy resins, and other difunctional phenol diglycidyl ether compounds, difunctional alcohol diglycidyl ether compounds, and their halides and hydrogenated products. The molecular weight of these compounds may be any. Several kinds of these compounds can be used in combination. Further, components other than the bifunctional epoxy resin may be included as impurities.

The bifunctional phenols in the present invention may be any compounds having two phenolic hydroxyl groups, for example, monocyclic bifunctional phenols such as hydroquinone, resorcinol, catechol and polycyclic bifunctional phenols. Bisphenol A and these halides,
There are alkyl group-substituted products and the like. The molecular weight of these compounds may be any. Several kinds of these compounds can be used in combination. Further, components other than the bifunctional phenols may be included as impurities.

The alkali metal hydride and alkali metal borohydride catalysts used in the present invention are compounds having a catalytic ability to accelerate the etherification reaction of the epoxy group and the phenolic hydroxyl group, and include lithium hydride, sodium hydride and borohydride. Lithium hydride, sodium borohydride and the like.
These catalysts can be used in combination. Further, it may be used in combination with a catalyst such as an amine compound or an imidazole compound.

The solvent in the present invention dissolves the epoxy resin and the phenols, which are the raw materials, and is preferably an amide solvent. Examples of the amide solvent include formamide, N-methylformamide, N, N-dimethylformamide, acetamide, N-methylacetamide, N, N-dimethylacetamide, N, N, N ′, N′-tetramethylurea, 2 -Pyrrolidone, N-methylpyrrolidone, carbamic acid ester and the like. These amide solvents can be used in combination. Further, it may be used in combination with another solvent represented by a ketone type or an ether type.

As the production conditions in the present invention, the compounding equivalent ratio of the bifunctional epoxy resin and the bifunctional phenol is preferably epoxy group / phenolic hydroxyl group = 1: 0.9 to 1.1.
If the amount is less than 0.9 equivalent, the polymer does not linearly increase in molecular weight, and a side reaction occurs to crosslink and become insoluble in the solvent. If the amount is more than 1.1 equivalent, the molecular weight does not increase.

The amount of the catalyst compounded is not particularly limited, but generally 0.0001 to 0.2 mol of the catalyst is contained with respect to 1 mol of the epoxy resin.
If the amount is less than this range, the high molecular weight reaction is remarkably slow, and if it is more than this range, side reactions increase and the linear molecular weight does not increase.

The synthetic reaction temperature during production is preferably 60 to 150 ° C. If the temperature is lower than 60 ° C, the high molecular weight reaction is extremely slow,
If the temperature is higher than ℃, side reactions will increase and the polymer will not linearly increase in molecular weight. Generally, it is desirable that the solid content concentration in the synthetic reaction during production is 30% or less. When the concentration is higher than this range, there are many side reactions and the molecular weight does not linearly increase.

Epoxy resin obtained by the present invention is an ultra-high molecular weight epoxy resin having film forming ability, compared to conventional high molecular weight epoxy resin, less branching, it is considered that further high molecular weight is advanced, It has a film forming ability of various strengths.

The obtained film has properties that cannot be realized by a film formed using a conventional high molecular weight epoxy resin. That is, the strength is remarkably large and the elongation is remarkably large.

Another feature of the present invention is that by selecting an alkali metal hydride or an alkali metal borohydride as a polymerization reaction catalyst, the polymerization reaction proceeds remarkably faster than when other catalysts are used. To be

(Example) Hereinafter, the present invention will be described in detail based on examples, but the present invention is not limited thereto.

Example 1 177.5 g of bisphenol A type epoxy resin (epoxy equivalent: 177.5) as a bifunctional epoxy resin and bisphenol A (hydroxyl equivalent: 115.5) as a bifunctional phenol 115.5
g, 0.24 g of lithium hydride as an etherification catalyst
It was dissolved in 684.2 g of dimethylacetamide to make the solid content concentration in the reaction system 30%. While stirring this mechanically,
Keep the temperature in the reaction system at 120 ° C in a 125 ° C oil bath,
It was kept as it was for 4 hours. As a result, the viscosity is 7,850 mPa
A high molecular weight epoxy resin solution of s was obtained. The weight average molecular weight of this epoxy resin was 128,000 as a result of measurement by gel permeation chromatography and 92,000 as a result of measurement by a light scattering method. Also, the reduced viscosity of this dilute solution of high molecular weight epoxy resin is (0.742dl / g)
Met. This high molecular weight epoxy resin solution was applied to a glass plate and dried at 200 ° C. for 1 hour to obtain an epoxy resin film having a thickness of 30 μm. The tensile strength of this film
The elastic modulus was 36.8 MPa, the elongation was 52.0%, and the tensile elastic modulus was 425 MPa. The glass transition temperature is 104 ° C and the thermal decomposition temperature is 345 ° C.
Met.

Example 2 177.5 g of bisphenol A type epoxy resin (epoxy equivalent: 177.5) as a bifunctional epoxy resin and bisphenol A (hydroxyl equivalent: 115.5) as a bifunctional phenol 115.5
g, lithium borohydride 0.65 g as an etherification catalyst N,
It was dissolved in 1,175 g of N-dimethylformamide to adjust the solid content concentration in the reaction system to 20%. While mechanically stirring this, the temperature in the reaction system was kept at 120 ° C. in an oil bath at 125 ° C. and kept as it was for 4 hours. As a result, the viscosity is 1,650 m
A high molecular weight epoxy resin solution of Pa · s was obtained. The weight average molecular weight of this epoxy resin was 115,000 as a result of measurement by gel permeation chromatography and 102,000 as a result of measurement by a light scattering method. The reduced viscosity of this dilute solution of high molecular weight epoxy resin is 0.742 (d
l / g). This high molecular weight epoxy resin solution was applied to a glass plate and dried at 200 ° C. for 1 hour to obtain an epoxy resin film having a thickness of 27 μm. This film has a tensile strength of 32.8MPa, an elongation of 42.5% and a tensile modulus of 410MP.
It was a. The glass transition temperature is 102 ° C and the thermal decomposition temperature is
It was 340 ° C.

Example 3 177.5 g of bisphenol A type epoxy resin (epoxy equivalent: 177.5) as a bifunctional epoxy resin and bisphenol A (hydroxyl equivalent: 115.5) as a bifunctional phenol 115.5
g, 1.13 g of sodium borohydride as an etherification catalyst were dissolved in 882.4 g of N-methylpyrrolidone to make the solid content concentration in the reaction system 25%. While stirring this mechanically 12
The temperature in the reaction system was kept at 120 ° C. in an oil bath at 5 ° C., and kept as it was for 4 hours. As a result, the viscosity is 3,680 mPas
A high molecular weight epoxy resin solution was obtained. The weight average molecular weight of this epoxy resin was 108,000 as a result of measurement by gel permeation chromatography and 87,000 as a result of measurement by a light scattering method. The reduced viscosity of this dilute solution of the high molecular weight epoxy resin was 0.805 (dl / g). This high molecular weight epoxy resin solution was applied to a glass plate and dried at 200 ° C. for 1 hour to obtain an epoxy resin film having a thickness of 33 μm. The tensile strength of this film is 3
The tensile modulus was 7.2 MPa, the elongation was 55.0%, and the tensile modulus was 410 MPa. The glass transition temperature was 103 ° C and the thermal decomposition temperature was 345 ° C.

Example 4 173.2 g of a bisphenol A type epoxy resin (epoxy equivalent: 173.2) as a bifunctional epoxy resin, 55.3 g of hydroquinone (hydroxyl equivalent: 55.3) as a bifunctional phenol, and 0.24 g of lithium hydride as an etherification catalyst were N-methyl. Dissolve pyrrolidone in 915.0 g and adjust the solid content concentration in the reaction system to 20
%. While mechanically stirring this, keep the temperature in the reaction system at 100 ° C in an oil bath at 110 ° C, and
Held for hours. As a result, a high molecular weight epoxy resin solution having a viscosity of 2,875 mPa · s was obtained. The weight average molecular weight of this epoxy resin was 123,000 as a result of measurement by gel permeation chromatography and 88,500 as a result of measurement by a light scattering method. The reduced viscosity of the dilute solution of the high molecular weight epoxy resin was 0.850 (dl / g).
Apply this high molecular weight epoxy resin solution to a glass plate and
After drying at 0 ° C. for 1 hour, an epoxy resin film having a thickness of 33 μm was obtained. The tensile strength of this film is 29.5MPa,
The elongation was 46.5% and the tensile elastic modulus was 395 MPa. The glass transition temperature was 82 ° C and the thermal decomposition temperature was 350 ° C.

Example 5 173.2 g of a bisphenol A type epoxy resin (epoxy equivalent: 173.2) as a bifunctional epoxy resin, 55.3 g of hydroquinone (hydroxyl equivalent: 55.3) as a bifunctional phenol, and 0.65 g of lithium borohydride as an etherification catalyst were added to N, It was dissolved in 687.5 g of N-dimethylacetamide to make the solid content concentration in the reaction system 25%. While stirring this mechanically, 110
The temperature in the reaction system was kept at 100 ° C in an oil bath at ℃, and kept as such for 4 hours. As a result, the viscosity is 4,080 mPas
A high molecular weight epoxy resin solution was obtained. The weight average molecular weight of this epoxy resin was 106,000 as a result of measurement by gel permeation chromatography and 88,000 as a result of measurement by a light scattering method. The reduced viscosity of the dilute solution of the high molecular weight epoxy resin was 0.790 (dl / g). This high molecular weight epoxy resin solution was applied to a glass plate and dried at 200 ° C. for 1 hour to obtain an epoxy resin film having a thickness of 32 μm. The tensile strength of this film is 3
The elongation was 8.3 MPa, the elongation was 42%, and the tensile elastic modulus was 390 MPa. The glass transition temperature was 82 ° C and the thermal decomposition temperature was 340 ° C.

Example 6 173.2 g of a bisphenol A type epoxy resin (epoxy equivalent: 173.2) as a bifunctional epoxy resin, 55.30 hydroquinone (a hydroxyl group equivalent: 55.3) as a bifunctional phenol, and 1.13 g of sodium borohydride as an etherification catalyst N, N -Dissolved in 535.8 g of dimethylformamide, the solid content concentration in the reaction system was adjusted to 30%. While stirring this mechanically, 11
The temperature in the reaction system was kept at 100 ° C. in an oil bath at 0 ° C., and kept as such for 4 hours. As a result, the viscosity is 6,890 mPas
A high molecular weight epoxy resin solution was obtained. The weight average molecular weight of this epoxy resin was 96,700 as measured by gel permeation chromatography and 82,500 as measured by light scattering method. The reduced viscosity of the dilute solution of this high molecular weight epoxy resin was 0.825 (dl / g). This high molecular weight epoxy resin solution was applied to a glass plate and dried at 200 ° C. for 1 hour to obtain an epoxy resin film having a thickness of 33 μm. The tensile strength of this film is 38.3
MPa, elongation was 45.8%, and tensile elastic modulus was 385 MPa. The glass transition temperature was 82 ° C and the thermal decomposition temperature was 345 ° C.

Example 7 171.3 g of a bisphenol A type epoxy resin (epoxy equivalent: 171.3) as a bifunctional epoxy resin, 55.4 g of resorcinol (a hydroxyl equivalent: 55.4) as a bifunctional phenol, and 1.13 g of lithium hydride as an etherification catalyst. -Dissolved in 683.5 g of dimethylformamide, the solid content concentration in the reaction system was adjusted to 25%. While stirring this mechanically, 115 ℃
The temperature in the reaction system was maintained at 110 ° C. in the oil bath described in (1) and maintained as it was for 4 hours. As a result, a high molecular weight epoxy resin solution having a viscosity of 3,054 mPa · s was obtained. The weight average molecular weight of this epoxy resin was 114,000 as measured by gel permeation chromatography and 84,600 as measured by light scattering method. The reduced viscosity of this dilute solution of the high molecular weight epoxy resin was 0.812 (dl / g). This high molecular weight epoxy resin solution was applied to a glass plate and dried at 200 ° C. for 1 hour to obtain an epoxy resin film having a thickness of 34 μm. The tensile strength of this film is 42.0
MPa, elongation was 48.0%, and tensile elastic modulus was 370 MPa. The glass transition temperature was 80 ° C and the thermal decomposition temperature was 345 ° C.

Example 8 171.3 g of a bisphenol A type epoxy resin (epoxy equivalent: 171.3) as a bifunctional epoxy resin and resorcinol (a hydroxyl group of 5 g was dissolved in 53-0.5 g of N-methylpyrrolidone as a bifunctional phenol) to obtain a solid content concentration in the reaction system. The temperature in the reaction system was kept at 110 ° C in an oil bath at 115 ° C for 4 hours while mechanically stirring it, and the temperature was kept as it was for 4 hours, as a result, a high molecular weight having a viscosity of 5,580 mPa · s was obtained. An epoxy resin solution was obtained, and the weight average molecular weight of this epoxy resin was 103,000 as measured by gel permeation chromatography and 72,400 as measured by the light scattering method. The reduced viscosity of the solution was 0.785 (dl / g).
After drying for 1 hour, an epoxy resin film having a thickness of 32 μm was obtained. The tensile strength of this film is 32.6 MPa.
The tensile modulus was 40.0% and 375 MPa. The glass transition temperature was 80 ° C and the thermal decomposition temperature was 340 ° C.

Example 9 171.3 g of bisphenol A type epoxy resin (epoxy equivalent: 171.3) as a bifunctional epoxy resin, resorcinol (hydroxyl equivalent: 55.4) 55.4 g as a bifunctional phenol,
As an etherification catalyst, 0.72 g of sodium hydride was dissolved in 919.7 g of N-methylpyrrolidone to adjust the solid content concentration in the reaction system to 20%. While stirring this mechanically, 115 ℃
The temperature in the reaction system was maintained at 110 ° C. in the oil bath described in (1) and maintained as it was for 4 hours. As a result, a high molecular weight epoxy resin solution having a viscosity of 1.54 mPa · s was obtained. The weight average molecular weight of this epoxy resin was 108,000 as a result of measurement by gel permeation chromatography, and 92,400 as a result of measurement by a light scattering method. The reduced viscosity of this dilute solution of high molecular weight epoxy resin was 0.752 (dl / g). This high molecular weight epoxy resin solution was applied to a glass plate and dried at 200 ° C. for 1 hour to obtain an epoxy resin film having a thickness of 29 μm. The tensile strength of this film is 36.3
The MPa. Elongation was 41.5% and the tensile elastic modulus was 380 MPa.
The glass transition temperature was 79 ° C and the thermal decomposition temperature was 345 ° C.

Comparative Example 1 The compounding amount of bisphenol A in Example 1 was changed from 115.5 g (1.00 equivalent to the epoxy resin) to 80.9 g (0.70 equivalent to the epoxy resin), and the compounding amount of N, N-dimethylacetamide was 686.5 g. Example 1 was repeated except that the amount was changed to 605.7 g. As a result, it gelated after 1 hour and became insoluble in the solvent.

Comparative Example 2 The compounding amount of bisphenol A in Example 1 was changed from 115.5 g (1.00 equivalent to the epoxy resin) to 80.9 g (0.70 equivalent to the epoxy resin), and the compounding amount of N, N-dimethylacetamide was 686.5 g. The same procedure as in Example 1 was carried out except that the amount was changed to 605.7 g, but heating was stopped before gelation to obtain a high molecular weight epoxy resin solution having a viscosity of 890 mPa · s. The weight average molecular weight of the obtained resin was 93,000 as a result of measurement by gel permeation chromatography and 68,000 as a result of measurement by a light scattering method. The reduced viscosity of this dilute solution of high molecular weight epoxy resin is 0.490 (dl /
g). This high molecular weight epoxy resin solution was applied to a glass plate and dried at 200 ° C. for 1 hour, but an epoxy resin film of 100 μm or less having sufficient strength for handling was not obtained.

Comparative Example 3 The procedure of Example 1 was repeated except that methyl ethyl ketone was used instead of N, N-dimethylacetamide in Example 1, but the viscosity was 2.6 mPa · s 8 hours after the start of heating. The weight average molecular weight of the obtained resin is 1,500 in the result measured by gel permeation chromatography,
It could not be measured by the light scattering method. This high molecular weight epoxy resin solution was applied to a glass plate and dried at 200 ° C. for 1 hour, but no epoxy resin film was obtained.

Comparative Example 4 The procedure of Example 1 was repeated except that the N, N-dimethylacetamide in Example 1 was changed to ethylene glycol monomethyl ether, but the viscosity after 8 hours from the start of heating was 78.2 mPa · s. It was The weight average molecular weight of the obtained resin was 29,300 as measured by gel permeation chromatography and 23,000 as measured by light scattering method.
Met.

Apply this high molecular weight epoxy resin solution to a glass plate and
It was dried at 0 ℃ for 1 hour, but 100μ of sufficient strength for handling.
No epoxy resin film having a thickness of m or less was obtained.

Comparative Example 5 The average molecular weight of phenoxy resin YP50P (Toto Kasei), which is a high molecular weight epoxy resin, was measured. Styrene equivalent weight average molecular weight by gel permeation chromatography is 68,000,
The average molecular weight by light scattering method was 77,000. The resin dissolved readily in methyl ethyl ketone. The viscosity of a 20% solution of N, N-dimethylacetamide was 206 mPa · s. An attempt was made to prepare an epoxy resin film by coating this high molecular weight epoxy resin solution on a glass plate and heating and drying in a drier, but a film having a thickness of 100 μm or less was not obtained.

Details of the experimental methods in the above Examples and Comparative Examples are shown below. The phenol compounding equivalent is the compounding equivalent of phenols to 1.000 equivalents of the epoxy resin. Viscosity is EMD
It was measured using a viscometer (Tokyo Keiki Co., Ltd.). The column used for gel permeation chromatography (GPC) is TSKge1G60.
It is 00 + G5000 + G4000 + G3000 + G2000. The eluent is
Using N, N-dimethylacetamide, sample concentration is 2%
And After the relationship between the molecular weight and the elution time was obtained using styrene having various molecular weights, the molecular weight was calculated from the elution time to obtain the styrene-equivalent weight average molecular weight. As the light scattering photometer, DLS-700 manufactured by Otsuka Electronics Co., Ltd. was used. Tensile strength,
Tensilon manufactured by Toyo Baldwin was used for elongation and tensile modulus. The film sample size was 50 × 10 mm, and the pulling speed was 5 mm / min. The glass transition temperature (Tg) was measured using a 910 type differential scanning calorimeter (DSC) manufactured by DuPont. For the thermal decomposition temperature, the temperature reduction start temperature in air was used as the thermal decomposition temperature using a suggestive thermobalance TGD / 3000 manufactured by vacuum burying.

As shown in Comparative Examples 1 and 2, it is considered that when the compounding equivalent of the epoxy resin is excessive, there is a lot of branching, and the molecular weight is 90,000 or more, and the film has a high molecular weight of 100 μm or less. Could not be molded.

Further, as shown in Comparative Example 5, commercially available bisphenol A
Phenoxy resin, which is a type ultra-high molecular weight epoxy resin, also has a considerably high molecular weight, but is dissolved in methyl ethyl ketone, and the viscosity of the N, N-dimethylacetamide 20% solution is the ultra-high molecular weight epoxy resin solution of the present invention. It was significantly lower than the viscosity of. 100 for these resins
A film of less than μm could not be formed.

When the reaction was stopped halfway and the epoxy resin having a relatively low molecular weight was used in the same formulation as in Example 1, the film could be molded, but the strength was remarkably low.

In all of the examples, the polymerization reaction time was 4
Using the epoxy resin obtained as time, thickness 100μ
It is possible to obtain an epoxy resin film having a sufficient strength of m or less.

(Effect of the Invention) According to the method for producing an ultrahigh molecular weight epoxy resin of the present invention,
It is possible to obtain an ultrahigh molecular weight epoxy resin having an excellent film-forming ability which has never been obtained before in a very short reaction time.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Masami Arai, 1500 Ogawa, Shimodate, Ibaraki Shimodate, Hitachi, Ltd. Shimodate Research Laboratory (72) Ikuo Hoshi, 1500, Ogawa, Shimodate, Ibaraki Hitachi Chemical Co., Ltd. (56) Reference JP 59-136357 (JP, A) JP 58-149914 (JP, A) JP 60-262819 (JP, A) JP 63-30520 (JP, A) JP-A-62-242676 (JP, A) JP-A-1-121369 (JP, A) JP-B-49-35360 (JP, B1)

Claims (1)

[Claims] 1. A bifunctional epoxy resin and a bifunctional phenol are polymerized by heating in a polymerization reaction solvent in the presence of a catalyst,
In the method of producing a high molecular weight epoxy resin, the compounding equivalent ratio of the bifunctional epoxy resin and the bifunctional phenols,
Epoxy group / phenolic hydroxyl group = 1: 0.9 to 1.1, using one or more catalysts selected from lithium hydride, sodium hydride, lithium borohydride and sodium borohydride catalysts in amide solvents , Which does not dissolve in methyl ethyl ketone, which is characterized in that the solid content concentration during the polymerization reaction is 30% or less, and the reduced viscosity is 0.6 dl / g (30
C., N, N-dimethylacetamide) or higher.