JPH0434565B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a high molecular weight cresol novolak epoxy resin suitable for casting materials, resin varnishes for reinforcing glass fibers, and resins for powder coatings, and a method for producing the same. Since the cured product of the resin of the present invention has high heat resistance and mechanical strength, the resin of the present invention is useful as an electrical equipment sealant and an aircraft structural material. [Prior Art] Epoxy resins have excellent heat resistance, mechanical strength, and electrical properties, and are therefore widely used in fields such as paints, electrical insulation materials, casting materials, and structural materials. These epoxy resins are generally bisphenol A
Diglycidyl ether of bisphenol A, which has about two epoxy groups in one molecule and is produced from epichlorohydrin and epichlorohydrin, is widely used (Japanese Patent Application Laid-open Nos. 55-118920, 58-74726, and 58-74727).
No., Special Publication No. 32-1548, British Patent No. 1001364, etc.). In recent years, with the development of small electrical appliances, LSI, IC, and aerospace equipment, there has been a demand for epoxy resins that provide cured products with higher heat resistance and mechanical strength. Multifunctional epoxy resins have come into use. When a polyfunctional epoxy resin is used, the crosslinking density after the curing reaction becomes high, so that mechanical properties and electrical properties are improved. As such multifunctional epoxy resins, tetraepoxide of methylene dianiline, tetraepoxide of diaminodiphenylmethane, tetraglycidyl ether of tetraphenolethane, etc. are known, but these epoxy resins have a low molecular weight, and each molecule contains The number of epoxy groups is at most 4, and only cured products with a heat resistance temperature of slightly over 200°C have been obtained. Furthermore, epoxy resins having amino groups in their molecules have poor storage stability, tend to gel, and have high water absorption. Further, as the polyfunctional epoxy resin, polyepoxide of phenol novolac resin (for example, Epicoat 154 Yuka Ciel Epoxy Co., Ltd. trade name),
Ortho-cresol novolac resin polyepoxide (e.g. EOCN104S Nippon Kayaku Co., Ltd. trade name)
These materials have been put to practical use in insulating paints, semiconductor encapsulation materials, FRTP structural materials, printed wiring boards, etc. that require heat resistance and high strength. The number average molecular weight of phenol novolac or cresol novolac, which is a raw material for these epoxy resins, is 250 to 1000 and is expressed by the following formula. [In the formula, R is H or _CH3 , and m is 1 to 3
] Since the epoxy resin has a trinuclear to pentanuclear structure, the molecular weight of this epoxy resin is about 1,400 at most. Therefore, the heat resistance temperature of cured products of these epoxy resins is also high.
200℃, and the reality is that there is a desire for an epoxy resin with higher heat resistance. [Problems to be Solved by the Invention] An object of the present invention is to provide a polyfunctional epoxy resin that has heat resistance of 230° C. or higher and provides a cured product with excellent mechanical strength. [Solutions to solve the problem] In order to improve the heat resistance of the cured product, based on the knowledge that if the raw material cresol novolac is more polynuclear, an epoxy resin with more epoxy groups can be obtained. , a linear novolac resin with a number average molecular weight of 1500 or more and a softening point of 120°C or more that is soluble in organic solvents such as ethers and ketones (Japanese Patent Application No. 116510/1989), which the present inventor previously filed an application for. 59-131864) as a polyphenol raw material and reacting it with epichlorohydrin in the presence of caustic soda, it is possible to provide an epoxy resin that provides a cured product with excellent heat resistance, which is the object of the present invention. [Configuration of the Invention] The first aspect of the present invention is a linear high molecular weight cresol novolak having an epoxy equivalent of 176 to 280 and a number average molecular weight of 2000 to 7000 as measured by vapor pressure method in an N,N-dimethylacetamide solvent. It provides epoxy resins. The epoxy resin of the present invention can be represented by the following formula. [In the formula, R is bonded at the ortho or para position
CH ₃ and n is the number of repetitions.] The second aspect of the present invention is that the softening point is 120°C or higher, N, N
- An epoxy equivalent of 176 to 280 is obtained by reacting a linear high molecular weight cresol novolak resin with a number average molecular weight of 1500 or more as measured by vapor pressure method in a dimethylacetamide solvent and epihalohydrin in the presence of an alkali metal hydroxide. The present invention provides a method for producing a linear high molecular weight cresol novolak epoxy resin having a number average molecular weight of 2000 or more as measured by vapor pressure method in a N,N-dimethylacetamide solvent. (Cresol novolac resin) Cresol novolac resin, which is a raw material for epoxy resin, is made of ortho-cresol or ortho-cresol and para-cresol in a molar ratio of 10:0 to 1:9, as described in the specification of the earlier application. A mixture of cresol and aldehyde mixed in a proportion selected from aliphatic alcohols having 3 to 12 carbon atoms, glycol ethers having 3 to 6 carbon atoms, benzyl alcohol, and aliphatic carboxylic acids having 2 to 6 carbon atoms A linear polymer obtained by polycondensation in a solvent in the presence of an acidic catalyst, with a softening point of 120°C or higher and a number average molecular weight of 1500 or higher as measured by vapor pressure method in an N,N-dimethylacetamide solvent. It is. (Cresol) Even if the cresol to be reacted with aldehyde is orthocresol alone, less than 90 mol% of it,
Preferably 30 to 70 mol% may be replaced by para-cresol. The use of para-cresol contributes to improving the heat resistance of the resin, but reduces the solubility of the resin in solvents. (Aldehyde) As the aldehyde, formaldehyde or trioxane or paraformaldehyde, which generates formaldehyde by thermal decomposition, is used. In particular, trioxane or paraformaldehyde is preferred in order to reduce the water content in the reaction system. Formaldehyde is used in a ratio of 0.7 to 1.5 mol, preferably 0.9 to 1.3 mol, per 1 mol of phenols. If the aldehyde content is low, only low molecular weight cresol novolak resins can be obtained. Also,
If used in large quantities, the resin tends to gel. (Solvent) The alcohol used as the reaction solvent is suitably one with a high boiling point and good solubility for the novolak resin, and glycol ethers such as propanol, butanol, amyl alcohol, hexanol, methoxyethanol, ethoxyethanol, and butoxyethanol. , benzine alcohol, etc. Examples of organic carboxylic acids include formic acid, acetic acid, propionic acid, butyric acid, and the like. The solvent is 150 to 100 parts by weight of cresol.
Used in a proportion of 300 parts by weight. (Acidic Catalyst) As the catalyst, protonic acids such as hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid, toluenesulfonic acid, oxalic acid, methanesulfonic acid, and perchloric acid are used. Unexamined Japanese Patent Publication 1987-
Lewis acids such as boron trifluoride, boron trifluoride ether complex, aluminum trichloride, tin tetrachloride, and zinc chloride, which are preferred in Japanese Patent No. 113 and No. 56-92908, are unsuitable. The catalyst is 0.01 to 100 parts by weight of cresol.
It is used in a proportion of 20 parts by weight, preferably 1 to 15 parts by weight. (Polycondensation reaction) The reaction is carried out by charging the raw materials cresol, aldehyde, solvent and catalyst into a reaction vessel and slowly heating them while stirring to reach the reaction temperature, or by charging the raw materials cresol, reaction solvent and catalyst. After the reaction temperature is reached, a solution of aldehyde and a catalyst dissolved in an alcohol or carboxylic acid solvent is added, or the raw materials cresol, aldehyde, and solvent are placed in a reaction vessel and heated to near the reaction temperature while stirring. , by dropping a solvent in which the catalyst or acid catalyst is dissolved, or by any of the following methods. When producing a random copolymer resin of ortho-cresol and para-cresol, it is necessary to thoroughly mix both cresols in advance. The reaction is carried out at 95°C or higher, preferably 105°C to 150°C. At low temperatures, the reaction progresses slowly, and at high temperatures, gel components are likely to occur. If there is a lot of water in the reaction system, formaldehyde will be consumed in side reactions, the amount used for polymerization will decrease, and the molecular weight will not increase. Furthermore, if a high molecular weight novolac resin has a high water content, it will become insoluble in a solvent and will precipitate, resulting in a heterogeneous reaction, making it difficult to convert into a polymer. The reaction is carried out at a water content of 15% by weight or less, preferably 10% by weight or less. It is also effective to carry out the reaction using a solvent such as n-butanol, which is azeotropic with water and can be separated, while refluxing to remove water produced along with the reaction. (Purification) To separate the cresol novolac resin after the reaction is complete, if a water-soluble solvent such as methoxyethanol, ethoxyethanol, acetic acid, or formic acid is used as the solvent, it should be poured into 10 to 20 times the amount of water. Then, it is reprecipitated and recovered as a water-insoluble resin. Further, when a water-insoluble solvent is used as the solvent, the catalyst is removed by washing with water or neutralization, and then the solvent is distilled off and the molten resin is recovered by extraction. (Cresol novolak resin) Orthocresol novolak resin is made of carboxylic acids such as acetic acid and propionic acid; alkyl alcohols such as methanol, ethanol, and butanol; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; ethyl acetate, It is easily soluble in esters such as butyl acetate; ethers such as tetrahydrofuran and dioxane; and glycol ethers such as methoxyethanol and butoxyethanol. Furthermore, the resin obtained is a linear polymer because it is easily soluble in these various solvents and no insoluble gel content is observed. The number average molecular weight measured by VPO using methyl ethyl ketone as a solvent was 1500 to 5000, and the ratio Q of weight average molecular weight to number average molecular weight was measured using gel permeation chromatography using tetrahydrofuran as a solvent, and it was 1.5 to 12. . In addition, this resin was determined to be 120°C by the softening point measurement method, which measures the temperature at which the resin powder flows and becomes transparent under a microscope.
It exhibited a softening point of ~300°C. On the other hand, cresol novolak resin obtained from a mixture of ortho-cresol and para-cresol is
It is a random copolymer of tetrahydrofuran,
The obtained resin is a linear polymer because it is soluble in ethers such as dioxane, dimethylacetamide, and dimethylformamide, and no insoluble gel components are observed. The solubility in a solvent varies depending on the molar ratio of ortho-cresol and para-cresol and the molecular weight. The higher the molar ratio of para-cresol and the higher the molecular weight, the less soluble it becomes. For example, resins with a molar ratio of para-cresol and orthocresol of 5/5 and a softening point of 145°C or higher include ketones such as acetone and methyl ethyl ketone; glycol ethers such as methoxyethanol and ethoxyethanol; and esters such as ethyl acetate. ; It is soluble in epichlorohydrin, but poorly soluble in alcohols such as methanol and ethanol. Polymerization of para-cresol in ethoxyethanol with paraformaldehyde and a sulfuric acid catalyst produces a linear high molecular weight para-cresol novolak resin with a softening point of over 300°C. However, this resin has poor solubility in solvents, and is hardly soluble in the above-mentioned solvents except tetrahydrofuran, dioxane, dimethylformamide, and dimethylacetamide. [Epoxy Resin] There are two methods for producing polyglycidyl ether by reacting the high molecular weight linear cresol novolac resin with epihalohydrin. (1) Cresol novolac resin and excess epihalohydrin are reacted in the coexistence of an alkali metal hydroxide, and the addition reaction of epihalohydrin to the cresol novolac resin and the ring-closing reaction to form an epoxy ring are simultaneously performed to produce polyester. One-step method for producing glycidyl ether (2) Cresol novolak resin and excess epihalohydrin are subjected to an addition reaction in the presence of a catalyst such as a phosphonium salt or a quaternary ammonium salt, and then an alkali metal hydroxide is added to perform a ring-closing reaction. A two-step process for producing polyglycidyl ether. Of these two methods, the latter two-stage method is preferable to the one-stage method because the yield is higher and the content of high molecular weight substances in the obtained polyglycidyl ether is lower. In said one-step process, the reaction is carried out at a temperature in the range of 60-150°C, preferably 80-120°C. Phenolic properties contained in cresol novolak resin
The amount of epihalohydrin to be blended is 2 to 20 times, preferably 8 to 12 times, by mole per equivalent of OH. The alkali metal hydroxide is used in an amount of at least equimolar, preferably 1.05 to 1.5 times the mole of the phenol hydroxyl group of the cresol novolak resin. In addition, in the latter two-stage method, the first stage addition reaction is carried out at 40 to 150 °C, preferably 70 to 140 °C,
The subsequent ring-closing reaction is carried out at 20-150°C, preferably 40-80°C.
Performed at °C. The amount of catalyst is 0.1 to 5 mol % based on the cresol novolak resin, and the amounts of epihalohydrin and alkali metal hydroxide are the same as in the one-stage process. The subsequent ring-closing reaction in the one-stage method and the two-stage method may be carried out under normal pressure or reduced pressure (50 to 200 mmHg) while continuously removing the produced water from the system by azeotroping with epihalohydrin. After the completion of these reactions, the reaction solution is filtered through a filter aid (for example, celite, etc.) to remove by-product salts, and unreacted epihalohydrin is recovered under reduced pressure to obtain a product or the reaction solution is filtered. After recovering unreacted epihalohydrin under reduced pressure, it is dissolved in an organic solvent that is sparingly soluble in water, such as methyl isobutyl ketone, cyclohexanone, etc., and this solution is brought into contact with water or hot water to remove inorganic impurities such as common salt from the aqueous phase. The organic solvent is then distilled off for purification.
Alternatively, the resin solution may be dechlorinated in a water-soluble solvent such as dioxane or tetrahydrofuran, and the resin solution may be poured into 5 to 10 times the volume of water with stirring to purify by reprecipitation. Examples of the raw material epihalohydrin include epichlorohydrin, epipromohydrin, β-methylepichlorohydrin, and β-methylepipromohydrin. Furthermore, examples of the alkali metal hydroxide include potassium hydroxide and sodium hydroxide. Furthermore, examples of catalysts used in the first-stage addition reaction in the two-stage process include quaternary ammonium salts and phosphites. Examples of the quaternary ammonium salt include tetramethylammonium chloride, tetraethylammonium bromide, triethylmethylammonium chloride, tetraethylammonium iodide, and cetyltriethylammonium bromide. Phosphites include triphenylphosphonium halides (eg iodide, bromide, chloride), triphenylethylphosphonium diethyl phosphate and phosphonates. A particularly preferred catalyst is tetramethylammonium chloride or tetraethylammonium bromide. The high molecular weight cresol novolak epoxy resin produced in this way can be produced using the vapor pressure method (VPO) using dioxane or dimethylacetamide as a solvent.
The number average molecular weight measured by the method is 2000 to 7000. In addition, the resin powder softens under a microscope.
This is a softening point measurement method that measures the temperature at which the material becomes fluid and transparent, and indicates a softening point ranging from 100°C to a maximum of over 300°C. This linear high molecular weight cresol novolak epoxy resin is made from dioxane, dimethylacetamide,
Soluble in organic solvents such as tetrahydrofuran, methyl ethyl ketone, chloroform, and cyclohexanone. This cresol novolak epoxy resin can be used as an epoxy resin alone or in combination with other epoxy compounds. In other words, if this cresol novolac epoxy resin is used alone or in combination with one or more other epoxy compounds and is subjected to a curing (crosslinking) reaction with an appropriate curing agent, heat resistance and flexibility can be achieved. The cured product is highly flexible and impact resistant. There are no particular restrictions on the other epoxy compounds used in combination, and various epoxy compounds may be used in combination depending on the intended use. Other epoxy compounds used in combination include, for example, polyglycidyl ethers such as bisphenol A or bromobisphenol A; polyglycidyl esters such as phthalic acid and cyclohexanedicarboxylic acid; or polyglycidyl amines with aniline or toluidine, etc. These are used in combination with the high molecular weight cresol novolac epoxy resin of the present invention in a proportion of 10 to 80% by weight in the epoxy compound. (Curing Agent) As a curing agent for curing this cresol novolak epoxy resin, various curing agents similar to those used in known epoxy resins can be used. For example, aliphatic amines, aromatic amines, heterocyclic amines, Lewis acids such as boron trifluoride and their salts, organic acids, organic acid anhydrides, urea or their derivatives, and polymercaptans. Examples include the following. Specific examples include aromatic amines such as diaminodiphenylmethane, diaminodiphenyl sulfone, 2,4-diamino-m-xylene; 2-methylimidazole, 2,
Imidazole or imidazole substitutes such as 4,5-triphenylimidazole and 1-cyanoethyl-2-methylimidazole, or salts of these with organic acids; organic carboxylic acids such as fumaric acid, trimellitic acid, and hexahydrophthalic acid; phthalic anhydride acid, endomethylenetetrahydrophthalic anhydride,
Organic acid anhydrides such as hexahydrophthalic anhydride; urea derivatives such as dicyandiamide, melamine, and guanamine; aliphatic polyamines such as triethylenetetramine, diethylenetriamine, xylylene diamine, and isophorone diamine; and epoxy thereof such as ethylene oxide and propylene oxide. Compounds or adducts with acrylic compounds such as acrylonitrile and acrylic acid can be used. In addition, polyhydric phenols such as phenol novolac resin, cresol novolac resin, and tetrahydroxyphenylethane are used as a curing agent, and this and
If necessary, amines can be used as an accelerator and as a curing agent. Furthermore, in addition to the above-mentioned curing agent, this high molecular weight cresol novolak epoxy resin may optionally contain plasticizers, organic solvents, reactive diluents, extenders, fillers, reinforcing agents, pigments, flame retardants, etc. Various additives such as thickeners and flexibility-imparting agents can be blended. The cresol novolak epoxy resin of the present invention is a linear polymer that was previously considered impossible,
It has a higher molecular weight and a higher softening point than the cresol novolac epoxy resins known up to now.
Therefore, the cured product of the linear high molecular weight cresol novolak epoxy resin of the present invention has superior heat resistance and strength compared to conventional products. Therefore, this cresol novolak epoxy resin can be used in the fields of laminated materials, molding materials, adhesives, and paints. That is, a glass cloth is impregnated with a varnish in which a curable resin composition containing this epoxy resin and a curing agent is dissolved in a solvent such as tetrahydrofuran or methyl ethyl ketone, dried to form a prepreg, and then copper foil and several sheets of prepreg are layered and heated. By pressing, a copper-clad laminate for printed wiring boards can be manufactured. Further, a curing accelerator, a filler such as silica, and a lubricant are added to this composition, and the mixture is kneaded on heated rolls to produce a molding compound. This compound is further molded using a transfer molding machine or the like and used for semiconductor encapsulation and mechanical parts. Furthermore, an adhesive can be produced by blending a resin such as nylon, polyester, polyvinyl butyral, or carboxyl group-containing butadiene nitrile rubber with this curable resin composition, and adding a filler if necessary. Furthermore, a filler is added to the polymeric orthocresol novolac epoxy resin, curing agent, and curing accelerator, kneaded with heated rolls, cooled, crushed with a crusher, and classified with a sieve to prepare a powder coating. You can. Next, the present invention will be explained in more detail with reference to Examples. [Production example of novolac resin] Example 1 108 g of O-cresol, 32 g of paraformaldehyde, and 240 g of ethyl cellosolve were mixed with 10 g of sulfuric acid.
4 times at 115℃ with stirring.
A time reaction was performed. After the reaction was completed, 17 g of NaHCO ₃ and 30 g of water were added to neutralize it, and the reaction solution was poured into 2 water while stirring at high speed. After separating the precipitated resin, it was dried to obtain 115 g of resin. . This resin contains methanol, ethanol, phthanol, octanol, methyl cellosolve, ethyl cellosolve, tetrahydrofuran, dioxane,
It was soluble in acetone, methyl ethyl ketone, ethyl acetate, and epichlorohydrin, and no gel content was observed. When the molecular weight of this resin was measured by vapor pressure method (40℃ in methyl ethyl ketone), the number average molecular weight was
It was 2600. Further, the softening point of the resin determined by microscopy was 155°C. Furthermore, the Q value of the tetrahydrofuran solution was 3.0 as determined by gel permeation chromatography analysis. Example 2 54 g of p-cresol, 54 g of o-cresol, 32 g of paraformaldehyde, and ethyl cellosolve
240g of the solution was placed in a reactor together with 10g of sulfuric acid, and the mixture was reacted at 115°C for 4 hours with stirring. 17g after completion of reaction
After neutralization by adding NaHCO ₃ and 30 g of water, the reaction solution was poured into water 2 while stirring at high speed, and the precipitated resin was separated and dried to obtain 115 g of novolak resin. Vapor pressure method of this resin (methyl ethyl ketone, 40
℃) Mn is 2800, Q value by gel permeation chromatography analysis of tetrahydrofuran solution is 2.4, softening point by microscopy is 200
It was over ℃. In addition, this resin can be used for acetone, methyl ethyl ketone, methoxyethanol, ethoxyethanol,
Tetrahydrofuran, dioxane, dimethylformamide, dimethylacetamide, ethyl acetate,
It was soluble in epichlorohydrin. Example 3 108 g of o-cresol, 29.3 g of paraformaldehyde, and 240 g of n-butanol were placed in a reactor with 15 g of p-toluenesulfonic acid while stirring.
The reaction was carried out at a temperature of 110°C to 115°C for 4 hours. The reaction was carried out while removing the water produced at this time from the system using a separator. After the reaction was completed, the butanol phase was separated after neutralization and washing with 300 g of water containing 17 g of NaHCO ₃ , the butanol was distilled off by heating, the resin was extracted at 190°C, and the mixture was cooled to 115
g of resin was obtained. This o-cresol novolac resin had a number average molecular weight of 1900 and a softening point of 130°C. Example 1 60 g of the high molecular weight o-cresol novolac resin obtained in Production Example 1, 462.5 g of epichlorohydrin and 4.0 g of tetramethylammonium bromide were placed in a three-necked flask and heated under reflux (117°C) for 2 hours with stirring. The reaction was carried out. After that, the reaction solution was cooled to 60°C, a water separator was attached, 42g of sodium hydroxide was added, and under reduced pressure (150°C
The ring-closing reaction was carried out at ~100 mmHg). The produced water was continuously removed from the system by azeotroping with epichlorohydrin, and the reaction was terminated when the produced water reached 18 ml. 0.1 to 50 mmHg of unreacted epichlorohydrin,
The product was collected at 60 to 110° C., 120 g of dioxane was added to dissolve the product, and after separating the by-produced sodium chloride, it was further poured into 1 part of water with stirring, reprecipitated, and the resin was separated and dried. The resulting resin had an epoxy equivalent weight of 230 and a microscopic softening point of 126°C. In addition, the number average molecular weight determined by vapor pressure method was 3950. This resin is soluble in tetrahydrofuran, dioxane, dimethylformamide, dimethylacetamide, methyl ethyl ketone, cyclohexanone, methoxyethyl acetate, chloroform, benzene, toluene, xylene, methanol, ethanol, butanol, methoxyethanol, ethoxyethanol, butoxyethanol It was insoluble in The infrared absorption spectrum of this product is shown in FIG. Examples 2 and 3 High molecular weight cresol novolak epoxy resins were produced in the same manner as in Example 1, except that 60 g of each of the high molecular weight cresol novolak resins obtained in Production Examples 2 and 3 were used. The epoxy equivalent of this epoxy resin is 235 and 225, respectively.
The softening point measured by microscopy is 200℃ or higher, respectively.
It was 105℃. In addition, the number average molecular weights determined by vapor pressure method were 4200 and 2850, respectively. Comparative Example 1 108 g of o-cresol, 73 g of 37% formalin and 0.1 ml of concentrated hydrochloric acid were placed in a reactor and heated at 85°C for 1 hour.
The reaction was continued under reflux for an additional 4 hours. After the reaction, 100 g of water was added, the resin was allowed to settle, and the water was removed by decantation, followed by dehydration under reduced pressure of 100 mmHg, and the molten resin was taken out at 150°C.
After solidification, it was crushed. The number average molecular weight of this resin by vapor pressure method is 580
The softening point by microscopy was 73°C. 60 g of the thus obtained ortho-cresol novolac resin, 462.5 g of epichlorohydrin and 4.0 g of tetramethylammonium bromide were charged into a reaction vessel, followed by an addition reaction in the same manner as in Example 1, followed by dehydrochlorination and epoxidation with 42 g of sodium hydroxide. A resin was obtained by performing the same post-treatment as in Example 1. The epoxy equivalent of the resulting resin was 220, and the softening point by microscopy was 49°C (softening point by durance method was 70°C). Application Examples 1 and 2 25 parts of diaminodiphenylsulfone was added to 100 parts by weight of the high molecular weight cresol novolak epoxy resin obtained in Examples 1 and 3, and after melt-mixing at 180°C, the mixture was thoroughly degassed and the mixture was thoroughly degassed. The mixture was cast into a mold, pre-cured at 180°C for 1 hour, and post-cured at 240°C for 4 hours to obtain a cured product having the physical properties shown in Table 1. Comparative Application Example 1 A cured product was prepared in the same manner as Application Example 1, except that the cresol novolak epoxy resin obtained in Comparative Example 1 was used instead of the epoxy resin. Table 1 shows the physical properties of this cured product. Application example 3 To 100 parts by weight of the high molecular weight cresol novolac epoxy resin obtained in Example 2, a number average molecular weight of 400 was added.
48 parts of phenolic novolak resin, silica
200 parts of the mixture was mixed with 1 part of BF _3.2 methylimidazole salt, kneaded for 10 minutes with heated rolls at 150°C, cooled, crushed, and compression molded at a pressure of 80 kg/cm ² in a mold at 250°C. After a few minutes, the mold was removed and further post-cured at 240°C for 4 hours. Table 2 shows the physical properties of the cured product. Comparative Application Example 2 A cured product was prepared in the same manner as Application Example 3, except that the cresol novolak epoxy resin obtained in Comparative Example 1 was used as the epoxy resin. Table 2 physical properties
Shown below.

【table】

【table】

[Table] * Inflection point of linear expansion

[Brief explanation of drawings]

FIG. 1 is an infrared absorption spectrum diagram of the cresol novolak epoxy resin obtained in Example 1.

Claims (1)

[Claims] 1. The epoxy equivalent represented by the following formula is 176 to 280, and the number average molecular weight measured by vapor pressure method in N,N-dimethylacetamide solvent is 2000 to 7000,
Linear high molecular weight cresol novolac epoxy resin with a softening point of 100-300℃. [In the formula, R ¹ is CH ₃ bonded at the ortho or para position, and n is the number of repetitions.] 2 Softening point of 120°C or higher, measured by vapor pressure method in N,N-dimethylacetamide solvent A linear high molecular weight cresol novolak resin with a number average molecular weight of 1500 or more is reacted with epihalohydrin in the presence of an alkali metal hydroxide to increase the epoxy equivalent.
176-280, and the number average molecular weight measured by vapor pressure method in N,N-dimethylacetamide solvent.
A method of producing linear high molecular weight cresol novolac epoxy resin of 2000 or more. 3. The linear cresol novolac resin is a mixture of ortho-cresol or a mixed cresol obtained by mixing ortho-cresol and para-cresol at a molar ratio of 10:0 to 1:9, and an aldehyde having 3 to 12 carbon atoms.
of aliphatic alcohol, glycol ether having 3 to 6 carbon atoms, benzyl alcohol, and aliphatic carboxylic acid having 2 to 6 carbon atoms in the presence of an acidic catalyst. The manufacturing method according to claim 2, characterized in that: