TWI877461B - Epoxy resin mixture and its manufacturing method, epoxy resin composition and its hardened product - Google Patents

Abstract

The present invention provides an epoxy resin mixture, an epoxy resin composition and a cured product thereof showing high heat resistance and high elastic modulus. An epoxy resin mixture contains an epoxy resin represented by the following formula (1) and an epoxy compound represented by the following formula (2). (In formula (1), n is a repetitive number, representing a real number from 1 to 20)

Description

Epoxy resin mixture and its manufacturing method, epoxy resin composition and its hardened product

The present invention relates to an epoxy resin mixture and an epoxy resin composition providing a curable resin composition, wherein the curable resin composition is useful in insulating materials for electrical and electronic parts (high reliability semiconductor sealing materials, etc.), laminates (printed wiring boards, build-up substrates, etc.), various composite materials headed by fiber reinforced plastics (FRP), adhesives, coatings, etc., especially laminates, and is useful in metal foil laminates, insulating materials for build-up substrates, flexible substrate materials, etc.

Epoxy resins are widely used in electrical/electronic parts, structural materials, adhesives, coatings, etc. due to their workability and the excellent electrical properties, heat resistance, adhesion, and water absorption resistance of their cured products.

In recent years, in the field of semiconductor-related materials, power semiconductors that can handle higher voltages or currents than previous semiconductors have been developed and used in order to achieve higher functionality or performance. Power semiconductors are mainly used in power conversion such as changing voltage or frequency or switching between DC and AC, thereby rotating motors with high precision, or sending generated electricity to the power grid without waste, thereby stably supplying power to home appliances and electrical equipment.

Since power semiconductors process very large amounts of electricity, they generate heat and reach high temperatures during use, which can cause failures. In order to ensure long-term high-temperature operation of power semiconductors, reliability tests called hot and cold cycle tests are performed, in which more than 1,000 cycles are repeated between -55°C and 150°C. Therefore, resin materials for power semiconductors are required to have heat resistance of more than 150°C (Patent Documents 1 to 4).

In the semiconductor-related field, in addition to the high functionality and performance of power semiconductors, the development of package substrates required for mounting chips is also being promoted to be thinner. As the package substrate becomes thinner, rigidity becomes necessary. Substrate materials with insufficient rigidity cannot withstand warping and thus cause damage. Therefore, resin materials widely used in substrate materials are required to have a high modulus of elasticity.

In addition to packaging substrates, there are also a large number of materials that require a high elastic modulus for resin materials. One of them is carbon fiber reinforced plastic (CFRP). Regarding CFRP, by completely embedding the resin material into the carbon fiber, the stress is transmitted to the fiber through the resin when the load is applied, so many parts of the carbon fiber can effectively bear the load at the same time. The elastic modulus of the resin material used at this time is high, which can suppress the buckling of the carbon fiber caused by the stress generated when the load is applied, thereby showing the strength of CFRP. In the case of a low elastic modulus of the resin material, the carbon fiber is easily buckled by the stress, and the strength of CFRP cannot be well demonstrated, which will lead to damage. Therefore, a slightly higher modulus of elasticity is desired for the resin material used in CFRP.

Patent document 5 discloses a resin composition formed by combining an epoxy resin having a skeleton of neopentyl glycol, 1,4-butanediol, and 1,6-hexanediol with a bisphenol A type epoxy resin. Although the composition exhibits excellent heat resistance and elastic modulus, the heat resistance does not reach 150°C, and the elastic modulus is not a sufficient value. [Prior art document] [Patent document]

[Patent Document 1] Japanese Patent Publication No. 2021-019123 [Patent Document 2] Japanese Patent Publication No. 2021-031323 [Patent Document 3] Japanese Patent Publication No. 2020-035721 [Patent Document 4] Japanese Patent Publication No. 2021-027150 [Patent Document 5] International Publication No. 2020/250957

[Problem to be solved by the invention] The present invention is made in view of this situation, and its purpose is to provide an epoxy resin mixture, epoxy resin composition and hardened product showing high heat resistance and high modulus of elasticity. [Means for solving the problem]

The inventors of the present invention have conducted diligent research and found that by containing a specific ratio of an epoxy compound having a specific structure relative to an epoxy resin having a specific structure, the cured product has high heat resistance and high elastic modulus, thereby completing the present invention.

That is, the present invention is as shown in the following [1] to [5]. [1] An epoxy resin mixture contains an epoxy resin represented by the following formula (1) and an epoxy compound represented by the following formula (2).

[Chemistry 1]

(In formula (1), n is a repetitive number, representing a real number from 1 to 20)

[Chemistry 2]

[2] The epoxy resin mixture as described in the above item [1], wherein, in a gas chromatography analysis, when the content of the epoxy resin in which n in the above formula (1) is 1 is set to 100 volume %, the content of the epoxy compound represented by the above formula (2) is 1.0 volume % to 10.0 volume %. [3] An epoxy resin composition comprising the epoxy resin mixture as described in the above item [1] or [2] and a curing agent. [4] A cured product obtained by curing the epoxy resin composition as described in the above item [3]. [5] A method for producing an epoxy resin mixture as described in the above item [1] or [2], wherein the epoxy resin mixture is obtained by reacting epichlorohydrin with a phenol resin represented by the following formula (3) and a phenol compound represented by the following formula (4).

[Chemistry 3]

(In formula (3), n is a repetitive number, representing a real number from 1 to 20)

[Chemistry 4] [Effect of invention]

According to the present invention, an epoxy resin, an epoxy resin composition, and a cured product using the epoxy resin composition can be provided, wherein the cured product has high heat resistance and high elastic modulus. Therefore, the epoxy resin composition is useful in power semiconductors, circuit boards, FRP, and the like.

The epoxy resin mixture of the present invention contains an epoxy resin represented by the following formula (1) and an epoxy compound represented by the following formula (2).

[Chemistry 5]

(In formula (1), n is a repetitive number, representing a real number from 1 to 20)

[Chemistry 6]

In the above formula (1), the value of n can be obtained by gel permeation chromatography (GPC, detector: RI (refractive index)). n is usually a real number of 1 to 20, preferably 1 to 10, and more preferably 1 to 5. If n is greater than 20, the molecular weight increases and the viscosity becomes high, so the processability is poor. In addition, the average value of n can be calculated based on the number average molecular weight obtained by gel permeation chromatography (GPC, detector: RI) or the area ratio of each separated peak. The average value of n is preferably 1 to 10, more preferably 1.1 to 10, and particularly preferably 1.1 to 5.

The epoxy equivalent of the epoxy resin mixture containing the epoxy resin represented by the formula (1) and the epoxy compound represented by the formula (2) is preferably in the range of 250 g/eq. or more and less than 400 g/eq., more preferably 280 g/eq. or more and less than 350 g/eq., and particularly preferably 290 g/eq. or more and less than 320 g/eq. When the epoxy equivalent of the epoxy resin mixture is less than 250 g/eq., although the crosslinking density increases and the heat resistance improves, the mixture becomes hard and brittle, resulting in a decrease in mechanical strength, which is not preferable. In addition, when the epoxy equivalent of the epoxy resin mixture is 600 g/eq. or more, although the crosslinking density is reduced and the brittleness of the cured product is improved, it leads to a decrease in heat resistance, which is not preferable. When the epoxy equivalent is appropriate, the heat resistance of the cured product can be improved without causing a decrease in mechanical strength.

In the present invention, the epoxy equivalent is measured by the method described in Japanese Industrial Standards (JIS) K-7236.

The softening point of the epoxy resin mixture of the present invention is preferably in the range of 60° C. to 80° C., more preferably 65° C. to 70° C. When the softening point is in the above range, the resins will not adhere to each other at room temperature, and thus the handling property is excellent.

The content of the epoxy compound represented by the formula (2) can be measured by GC (gas chromatography) analysis and can be confirmed based on the area % of the detected peak. The GC analysis of the present invention is performed by the method described in the embodiments described below. In the GC analysis, when the content of the epoxy resin in which n of the formula (1) is 1 is set to 100 area %, the content of the epoxy compound represented by the formula (2) is preferably 1.0 area % to 10.0 area %, more preferably 1.0 area % to 8.0 area %, further preferably 1.0 area % to 6.0 area %, particularly preferably 2.0 area % to 6.0 area %, and most preferably 2.0 area % to 4.0 area %. A free volume is generated in the three-dimensional network of the cured epoxy resin mixture. Since the epoxy compound represented by the formula (2) has only one functional group, if its content is 1.0 area % or more, the free volume can be reduced, so that the three-dimensional network is difficult to move, and the heat resistance or elastic modulus is improved. If the content of the epoxy compound represented by the formula (2) is more than 10.0 area %, the free volume becomes smaller, but since there is an excess of the epoxy compound represented by the formula (2) that cannot completely enter the free volume, the low molecular weight components increase, and the heat resistance or elastic modulus decreases. Therefore, the content of the epoxy compound represented by the formula (2) is preferably within the above range.

The epoxy resin mixture of the present invention has excellent heat resistance and elastic modulus. The heat resistance is preferably above 150°C, more preferably above 155°C, and particularly preferably above 160°C. If the heat resistance is low, the molecular movement will become intense when used in places such as power components that operate at higher temperatures and for longer periods of time than before, which may cause damage. In addition, in thin substrates such as packaging substrates, rigidity, that is, the elastic modulus of the cured product, is required. If the rigidity is low, the substrate is prone to warping and there is a concern of damage. Therefore, a high elastic modulus is required for thin substrates. The elastic modulus of the epoxy resin material is preferably above 2.8 GPa in a bending test at 30°C, and more preferably above 2.9 GPa.

The epoxy resin represented by the formula (1) and the epoxy compound represented by the formula (2) can be obtained by reacting a phenol resin represented by the following formula (3) and a phenol compound represented by the following formula (4) with epichlorohydrin.

[Chemistry 7]

(In formula (3), n is a repetitive number, representing a real number from 1 to 20)

[Chemistry 8]

The value of n in formula (3) and the preferred range are the same as those in formula (1).

As a method for synthesizing the phenol resin represented by the formula (3), there can be mentioned a reaction between phenol and 4,4'-bischloromethylbiphenyl. In this case, the amount of 4,4'-bischloromethylbiphenyl used is usually in the range of 1 mol to 9 mol, preferably 2 mol to 8 mol, based on 10 mol of phenol.

Specific examples of the alkaline substance that can be used in the reaction include: alkali metal hydroxides such as lithium hydroxide, sodium hydroxide, and potassium hydroxide; alkali earth metal hydroxides such as magnesium hydroxide, calcium hydroxide, and barium hydroxide; alkali earth metal oxides such as magnesium oxide and calcium oxide; sodium acetate, potassium acetate, sodium oxalate, potassium oxalate, sodium formate, potassium formate, calcium acetate, magnesium acetate, and ammonium acetate. , sodium carbonate, potassium carbonate, calcium carbonate, magnesium carbonate, ammonium carbonate, sodium bicarbonate, potassium bicarbonate, ammonium bicarbonate, trisodium citrate, tripotassium citrate, sodium tartrate, potassium tartrate, sodium phosphate, sodium tripolyphosphate, sodium monohydrogen phosphate, sodium dihydrogen phosphate, sodium methoxide, sodium ethoxide, potassium tert-butoxide, potassium ethoxide and the like alkali metal alkoxides; sodium phenoxide, potassium phenoxide and the like, but not limited to these. In addition, these may be used alone or in combination of two or more. The amount of the alkaline substances used is generally in the range of 0.02 mol to 2.0 mol, preferably 0.05 mol to 2.0 mol, relative to 1 mol of 4,4'-bischloromethylbiphenyl.

Specific examples of solvents that can be used in the reaction include, but are not limited to, alcohols such as methanol, ethanol, and propanol; ketones such as methyl ethyl ketone and methyl isobutyl ketone; diethylene glycol, acetic acid, and the like. In addition, these solvents can be used alone or in combination of two or more. The amount of these solvents used is generally in the range of 5 to 200 parts by weight, preferably 10 to 100 parts by weight, relative to 100 parts by weight of phenol.

In the reaction, by using toluene together with the solvent, the phenol compound represented by the formula (4) can be obtained. The amount of toluene used is generally in the range of 5 to 200 parts by weight, preferably 10 to 100 parts by weight, relative to 100 parts by weight of phenol. When more than 200 parts by weight of toluene is used, a large amount of the phenol compound represented by the formula (4) is generated, and as a result, a large amount of the epoxy compound represented by the formula (2) is generated, so the heat resistance is greatly reduced. On the other hand, when less than 5 parts by weight of toluene is used, the amount of the phenol compound represented by the formula (4) generated decreases, and as a result, the amount of the epoxy compound represented by the formula (2) generated decreases, resulting in a low elastic modulus. Therefore, it is preferred to use toluene within the above range.

Regarding the reaction, it is usually preferred to charge phenol and the alkaline substance and gradually add 4,4'-bischloromethylbiphenyl thereto. The temperature at this time is usually in the range of 50°C to 150°C, preferably 60°C to 120°C, and is usually 0.5 hours to 10 hours, preferably 1 hour to 4 hours. In the case of a reaction at a temperature less than 50°C, toluene is difficult to react, that is, it is difficult to generate the epoxy compound represented by the formula (2). In addition, if it exceeds 150°C, toluene will volatilize and will not contribute to the reaction. After the addition of 4,4'-bischloromethylbiphenyl is completed, the reaction is carried out at a temperature of usually 50°C to 150°C, preferably 60°C to 120°C, for usually 0.5 hours to 10 hours, preferably 1 hour to 5 hours. Furthermore, at this time, if the pH value of the reaction solution is not acidic, the reaction is hindered and sometimes the polymer is not formed. In this case, an acidic substance such as p-toluenesulfonic acid, hydrochloric acid, sulfuric acid, etc. is added to the reaction system. After the reaction is completed, the excess phenol is removed by distillation under heating and reduced pressure. Thereafter, the mixture is usually dissolved in a water-insoluble solvent and repeatedly washed with water to remove the salt, and the solvent is distilled off to obtain the phenol resin represented by the formula (3) and the phenol compound represented by the formula (4).

Next, the reaction for obtaining the epoxy resin mixture of the present invention is described. The epoxy resin represented by the formula (1) and the epoxy compound represented by the formula (2) are obtained by reacting the phenol resin represented by the formula (3) and the phenol compound represented by the formula (4) with epichlorohydrin, respectively.

Epichlorohydrin can be easily obtained from the market. The amount of epichlorohydrin used is generally 3.0 mol to 10 mol, preferably 3.5 mol to 8.0 mol, and more preferably 4.0 mol to 7.0 mol, relative to 1 mol of hydroxyl group of the raw material phenolic resin.

In the above reaction, an alkali metal hydroxide can be used as a catalyst to promote the epoxidation step. Examples of the alkali metal hydroxide that can be used include sodium hydroxide, potassium hydroxide, etc., and solids or aqueous solutions thereof can be used. In the present invention, solids formed into flakes are preferably used, especially in terms of solubility and handling. The amount of the alkali metal hydroxide used is generally 0.90 mol to 1.50 mol relative to 1 mol of the hydroxyl group of the raw material phenol resin.

In order to promote the reaction, a quaternary ammonium salt such as tetramethylammonium chloride, tetramethylammonium bromide, or trimethylbenzylammonium chloride may be added as a catalyst. The amount of the quaternary ammonium salt used is preferably 0.0009 mol to 0.15 mol per 1 mol of the hydroxyl group in the raw material phenol mixture.

The reaction temperature is usually 30°C to 90°C, preferably 35°C to 80°C. In particular, in the present invention, it is preferably above 50°C in order to perform higher purity epoxidation. The reaction time is usually 0.5 hours to 10 hours, preferably 1 hour to 8 hours, and particularly preferably 1 hour to 4 hours. If the reaction time is short, the reaction is not completely carried out, and if the reaction time is long, by-products are formed, which is not good. The reaction products of these epoxidation reactions are washed with water, or epichlorohydrin or solvent is removed under heating and reduced pressure without washing with water. In addition, in order to further produce an epoxy resin with less hydrolyzable halogen, a ketone compound with 4 to 7 carbon atoms (for example, methyl isobutyl ketone, methyl ethyl ketone, cyclopentanone, cyclohexanone, etc.) can be used as a solvent to dissolve the recovered epoxy resin, and an aqueous solution of an alkali metal hydroxide such as sodium hydroxide or potassium hydroxide is added and reacted to form a closed ring. In this case, the amount of the alkali metal hydroxide used is usually 0.01 mol to 0.3 mol relative to 1 mol of the hydroxyl group of the raw material phenol resin used in the epoxidation, the reaction temperature is usually 50°C to 120°C, and the reaction time is usually 0.5 hours to 2 hours.

After the reaction is completed, the generated salt is removed by filtering, washing with water, etc., and then the solvent is distilled off under heating and reduced pressure to obtain the epoxy resin mixture of the present invention.

The epoxy resin composition of the present invention contains a hardener. Examples of the hardener that can be used include phenol hardeners, acid anhydride hardeners, amide hardeners, and amine hardeners.

In the epoxy resin composition of the present invention, a phenolic curing agent is preferred in order to balance the heat resistance and thermal stability of the cured resin. Examples of the phenolic curing agent include phenol novolac resin, cresol novolac resin, phenol aralkyl resin; polyphenols (bisphenol A, bisphenol F, bisphenol S, fluorene bisphenol, terpene diphenol (terpene diphenol), 4,4'-dihydroxybiphenyl, 2,2'-dihydroxybiphenyl, 3,3',5,5'-tetramethyl-(1,1'-biphenyl)-4,4'-diphenol, hydroquinone, resorcinol, naphthalene diol, tris-(4-hydroxyphenyl)methane and 1,1,2,2-tetrakis(4-hydroxyphenyl)ethane, etc.); by phenols (such as phenol, alkyl-substituted phenols, naphthol, alkyl-substituted naphthols, dihydroxybenzene and dihydroxynaphthalene, etc.) and aldehydes (formaldehyde, acetaldehyde, benzaldehyde, p-hydroxybenzaldehyde, o-hydroxybenzaldehyde and furfural, etc.), ketones (p-hydroxybenzene Phenol resins obtained by condensation of phenols (e.g., bis(chloromethyl)-1,1'-biphenyl and 4,4'-bis(methoxymethyl)-1,1'-biphenyl) or substituted phenyls (e.g., 1,4-bis(chloromethyl)benzene, 1,4-bis(methoxymethyl)benzene and 1,4-bis(hydroxymethyl)benzene); modified products of the phenols and/or the phenol resins; halogenated phenols such as tetrabromobisphenol A and brominated phenol resins.

Examples of the acid anhydride hardener include phthalic anhydride, trimellitic anhydride, pyromellitic anhydride, maleic anhydride, tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, methylnadic anhydride, hexahydrophthalic anhydride, and methylhexahydrophthalic anhydride.

Examples of amide-based hardeners include dicyandiamide and polyamide resins synthesized from a dimer of linolenic acid and ethylenediamine.

As amine-based hardeners, 3,3'-diamino diphenyl sulfone (3,3'-DDS), 4,4'-diamino diphenyl sulfone (4,4'-DDS), diamino diphenyl methane (diamino diphenyl methane, DDM), 3,3'-diisopropyl-4,4'-diaminodiphenylmethane, 3,3'-di-tert-butyl-4,4'-diaminodiphenylmethane, 3,3'-diethyl-5,5'-dimethyl-4,4'-diaminodiphenylmethane, 3,3'-diisopropyl-5,5'-dimethyl-4,4'-diaminodiphenylmethane, 3,3'-di-tert-butyl-5,5'-dimethyl-4,4'-diaminodiphenylmethane, 3,3',5,5'-tetraethyl-4,4'-diamino Diphenylmethane, 3,3'-diisopropyl-5,5'-diethyl-4,4'-diaminodiphenylmethane, 3,3'-di-tert-butyl-5,5'-diethyl-4,4'-diaminodiphenylmethane, 3,3',5,5'-tetraisopropyl-4,4'-diaminodiphenylmethane, 3,3'-di-tert-butyl-5,5'-diisopropyl-4,4'-diaminodiphenylmethane, 3,3',5,5'-tetra-tert-butyl-4,4'-diaminodiphenylmethane, diaminodiphenyl ether (diamino diphenyl ether, DADPE), diphenylamine, benzyl dimethylaniline, 2-(dimethylaminomethyl)phenol (DMP-10), 2,4,6-tris(dimethylaminomethyl)phenol (DMP-30), 2-ethylhexanoate of 2,4,6-tris(dimethylaminomethyl)phenol, etc. In addition, there can be cited: aniline novolac, o-ethylaniline novolac, aniline resin obtained by the reaction of aniline and xylylene chloride, aniline resin obtained by the condensation of aniline and substituted biphenyls (4,4'-bis(chloromethyl)-1,1'-biphenyl and 4,4'-bis(methoxymethyl)-1,1'-biphenyl, etc.) or substituted phenyls (1,4-bis(chloromethyl)benzene, 1,4-bis(methoxymethyl)benzene and 1,4-bis(hydroxymethyl)benzene, etc.), etc.

In the epoxy resin composition of the present invention, the amount of the curing agent used is preferably 0.7 to 1.2 equivalents relative to 1 equivalent of epoxy group of the epoxy resin. If the amount is less than 0.7 equivalents or exceeds 1.2 equivalents relative to 1 equivalent of epoxy group, there is a concern that the curing may be incomplete and good curing properties may not be obtained.

In addition, a hardening accelerator may be formulated in the epoxy resin composition of the present invention as needed. The gelling time may also be adjusted by using a hardening accelerator. Examples of hardening accelerators that can be used include: imidazoles such as 2-methylimidazole, 2-ethylimidazole, and 2-ethyl-4-methylimidazole; tertiary amines such as 2-(dimethylaminomethyl)phenol and 1,8-diazobicyclo(5,4,0)undecene-7; phosphines such as triphenylphosphine; and metal compounds such as tin octanoate. The hardening accelerator is used in an amount of 0.01 to 5.0 parts by weight relative to 100 parts by weight of the epoxy resin as needed.

In the epoxy resin composition of the present invention, other epoxy resins may also be formulated, and specific examples thereof include: phenols (phenol, alkyl-substituted phenol, aromatic-substituted phenol, naphthol, alkyl-substituted naphthol, dihydroxybenzene, alkyl-substituted dihydroxybenzene, dihydroxynaphthalene, etc.) and various aldehydes (formaldehyde, acetaldehyde, alkyl aldehydes, benzaldehyde, alkyl-substituted benzaldehyde, hydroxybenzaldehyde, naphthaldehyde, glutaraldehyde, o-phthalaldehyde, etc.). Condensation products of phenols and various diene compounds (dicyclopentadiene, terpenes, vinylcyclohexene, norbornadiene, vinyl norbornene, tetrahydroindene, divinylbenzene, divinylbiphenyl, diisopropylbiphenyl, butadiene, isoprene, etc.), polymers of phenols and ketones (acetone, methyl ethyl ketone, methyl isobutyl ketone, acetophenone, benzophenone, etc.), by condensation of phenols and substituted biphenyls (4,4'-bis(chloromethyl)-1,1'-biphenyl and 4,4'-bis(methoxymethyl)-1,1'-biphenyl, etc.), or substituted phenyls (1,4-bis(chloromethyl)benzene, 1,4-bis(methoxymethyl)benzene and 1,4-bis(hydroxymethyl)benzene, etc.). The obtained phenol resins, polycondensates of diphenols and various aldehydes, glycidyl ether epoxy resins obtained by glycidylating alcohols, aliphatic epoxy resins represented by 4-vinyl-1-cyclohexene diepoxide or 3,4-epoxycyclohexylmethyl-3,4'-epoxycyclohexanecarboxylate, glycidylamine epoxy resins represented by tetraglycidyl diaminodiphenyl methane (TGDDM) or triglycidyl-p-aminophenol, glycidyl ester epoxy resins, etc., but are not limited to these as long as they are commonly used epoxy resins.

In the epoxy resin composition of the present invention, known additives may be formulated as needed. Specific examples of usable additives include: polybutadiene and modified products thereof, modified products of acrylonitrile copolymers, polyphenylene ether, polystyrene, polyethylene, polyimide, fluororesin, maleimide compounds, cyanate ester compounds, silicone gel, silicone oil, and inorganic fillers such as silicon dioxide, aluminum oxide, calcium carbonate, quartz powder, aluminum powder, graphite, talc, clay, iron oxide, titanium oxide, aluminum nitride, asbestos, mica, and glass powder, surface treatment agents for fillers such as silane coupling agents, mold release agents, and coloring agents such as carbon black, phthalocyanine blue, and phthalocyanine green.

The epoxy resin composition of the present invention may contain a known maleimide compound as required. Specific examples of maleimide compounds that can be used include 4,4'-diphenylmethane dimaleimide, polyphenylmethane maleimide, metaphenyl dimaleimide, 2,2'-bis[4-(4-maleimidephenoxy)phenyl]propane, 3,3'-dimethyl-5,5'-diethyl-4,4'- Diphenylmethane bismaleimide, 4-methyl-1,3-phenylene bismaleimide, 4,4'-diphenyl ether bismaleimide, 4,4'-diphenylsulfone bismaleimide, 1,3-bis(3-maleimidephenoxy)benzene, 1,3-bis(4-maleimidephenoxy)benzene, etc., but not limited to these. These can be used alone or in combination of two or more. When preparing the maleimide-based compound, a curing accelerator is prepared as needed, and the above-mentioned curing accelerator, or a free radical polymerization initiator such as an organic peroxide or an azo compound can be used.

The epoxy resin composition of the present invention can be added with an organic solvent to prepare a varnish-like composition (hereinafter referred to as varnish). Examples of the solvent used include: γ-butyrolactone; amide solvents such as N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, and N,N-dimethylimidazolidone; sulfones such as tetramethylene sulfone; ether solvents such as diethylene glycol dimethyl ether, diethylene glycol diethyl ether, propylene glycol, propylene glycol monomethyl ether, propylene glycol monomethyl ether monoacetate, and propylene glycol monobutyl ether; ketone solvents such as methyl ethyl ketone, methyl isobutyl ketone, cyclopentanone, and cyclohexanone; and aromatic solvents such as toluene and xylene. The solvent is used so that the solid content concentration of the obtained varnish after the solvent is removed is usually in the range of 10 to 80% by weight, preferably 20 to 70% by weight.

Next, the cured product, resin sheet, prepreg, and FRP of the present invention are described. The epoxy resin composition of the present invention can also be applied to one or both sides of a supporting substrate and used as a resin sheet. As the coating method, for example, there can be listed: a pouring method; a method of extruding the resin from a nozzle or a die using a pump or an extruder and adjusting the thickness using a scraper; a method of adjusting the thickness by calendering with a roller; a method of spraying using a sprayer, etc. Furthermore, in the step of forming the layer, it can also be carried out while heating within a temperature range that can avoid thermal decomposition of the epoxy resin composition. In addition, rolling treatment, grinding treatment, etc. can also be performed as needed. As supporting substrates, for example, porous substrates including paper, cloth, non-woven fabrics, etc., plastic films or sheets such as polyethylene, polypropylene, polyethylene terephthalate, polyester films, nets, foams, metal foils, and laminates of these, etc., can be listed, but it is not limited to these. There is no special restriction on the thickness of the supporting substrate, and it can be appropriately determined according to the purpose.

The prepreg of the present invention can be obtained by heating and melting the epoxy resin composition and/or the resin sheet of the present invention to reduce the viscosity and then impregnating the epoxy resin composition and/or the resin sheet into a fiber substrate.

Alternatively, the prepreg of the present invention may be obtained by impregnating a fiber substrate with a varnish-like epoxy resin composition and then heating and drying the prepreg. The prepreg is cut into a desired shape and laminated, and then the laminate is heated and cured while applying pressure to the laminate using a press molding method, an autoclave molding method, a sheet winding molding method, etc., to obtain the FRP of the present invention. Alternatively, copper foil or an organic film may be laminated during the prepreg lamination.

Furthermore, the FRP forming method of the present invention can be obtained by forming by the above method or by a known method. For example, the following resin transfer molding technology (RTM (Resin Transfer Molding) method) can also be used: a carbon fiber substrate (usually a carbon fiber fabric) is cut, layered, and shaped to make a preform (a preform before impregnation with resin), the preform is arranged in a forming mold and the mold is closed, the resin is injected to impregnate the preform and harden it, and then the mold is opened to take out the molded product. In addition, a type of RTM method such as Vacuum assist Resin Transfer Molding (VaRTM), Seeman's Composite Resin Infusion Molding Process (SCRIMP), and Controlled Atmospheric Pressure Resin Infusion (CAPRI) described in Japanese Patent No. 2005-527410 can also be used. The CAPRI method is to exhaust the resin supply tank until the pressure is lower than the atmospheric pressure, use cyclic compression, and control the net molding pressure, thereby more appropriately controlling the resin injection process, especially the VaRTM method.

Furthermore, the following methods may also be used: a film stacking method in which a fiber substrate is sandwiched between resin sheets (films); or a method in which a powdered resin is attached to a reinforced fiber substrate in order to improve impregnation; a forming method in which a fluidized layer or fluid slurry method is used in the process of mixing the resin with the fiber substrate (powder impregnated yarn); or a method in which resin fibers are interwoven with a fiber substrate.

Examples of carbon fibers include acrylic, pitch, rayon, and other carbon fibers. Among them, acrylic carbon fibers with high tensile strength are preferably used. As the form of the carbon fiber, twisted yarn, untwisted yarn, untwisted yarn, etc. can be used. However, in order to achieve a good balance between formability and strength properties of the fiber-reinforced composite material, untwisted yarn or untwisted yarn can be preferably used. [Example]

The present invention is further specifically described below by way of examples. The materials, processing contents, processing sequence, etc. shown below may be appropriately changed without departing from the gist of the present invention. Therefore, the scope of the present invention should not be limitedly interpreted by the specific examples shown below.

The various analysis methods were performed under the following conditions. • Epoxy equivalent Measured by the method described in JIS K-7236, the unit is g/eq. • Softening point Measured by the method in accordance with JIS K-7234, the unit is ℃. • Melt viscosity Measured by the ICI melt viscosity (150℃) cone plate method, the unit is Pa•s.

•GPC (Gel Permeation Chromatography) Analysis Manufacturer: Waters Device: Alliance Waters e2695 Column: Guard column SHODEX GPC KF-601 (2 pieces), KF-602 KF-602.5, KF-603 Flow rate: 1.23 ml/min. Column temperature: 25℃ Solvent used: THF (tetrahydrofuran) Detector: RI (differential refractometer)

•GC (gas chromatography) analysis Manufacturer: Agilent Technologies, Inc. Device: HP6890 Column: DB-5HT 30 m-0.25 mm-0.10 μm Carrier gas: He 1.2 mL/min. Oven: 150℃-10℃/min.-350℃ (40 min.) Inlet: split (30:1), 330℃ Detector: Flame Ionization Detector (FID) Detector temperature: 350℃

[Example 1] In a flask equipped with a stirrer, a reflux cooling tube, and a stirring device, 195 parts by weight of phenol, 50 parts by weight of sodium hydroxide in the form of flakes, 20 parts by weight of methanol, and 40 parts by weight of toluene were placed, stirred, and dissolved, and then heated to maintain the temperature at 100°C, while 151 parts by weight of 4,4'-bischloromethylbiphenyl was continuously added over a period of 4 hours. After the addition was completed, 11 parts by weight of p-toluenesulfonic acid was added, and the reaction was further carried out at the same temperature for 3 hours. After the reaction was completed, the by-produced sodium chloride was removed by washing with water, and the excess phenol was distilled off from the oil layer under heating and reduced pressure, and 400 parts by weight of methyl isobutyl ketone was added to the residue and dissolved. The resin solution was repeatedly washed with water until the washing liquid became neutral, and then methyl isobutyl ketone was distilled from the oil layer under heating and reduced pressure to obtain 180 parts by weight of phenol resin (P1).

[Example 2] Relative to 107 parts by weight of the phenolic resin (P1) obtained in Example 1, 230 parts by weight of epichlorohydrin and 60 parts by weight of dimethyl sulfoxide are placed in a reaction vessel, heated, stirred, and dissolved, and then the temperature is maintained at 45°C, and 21 parts by weight of sodium hydroxide in the form of flakes are continuously added for 2 hours. After the addition of sodium hydroxide is completed, the reaction is further carried out at 45°C for 2 hours and at 70°C for 1 hour. Then, after repeated water washing to remove by-product salts and dimethyl sulfoxide, excess epichlorohydrin is distilled from the oil layer under heating and reduced pressure, and 300 parts by weight of methyl isobutyl ketone is added to the residue and dissolved. The methyl isobutyl ketone solution was heated to 70°C, 10 parts by weight of a 30% aqueous sodium hydroxide solution was added, and after reacting for 1 hour, the reaction solution was repeatedly washed with water until the washing solution became neutral. Then, methyl isobutyl ketone was distilled off from the oil layer under heating and reduced pressure to obtain 130 parts by weight of an epoxy resin mixture (EP1). The GPC chart of the epoxy resin mixture (EP1) is shown in Figure 1. The epoxy equivalent of the epoxy resin mixture (EP1) is 312 g/eq., the softening point is 66.9°C, and the ICI melt viscosity is 0.25 Pa·s (150°C). In the GC analysis, when the content of the epoxy resin in formula (1) where n is 1 (peaks at 24.8 minutes, 26.5 minutes, and 28.4 minutes of A in Figure 4) is set to 100 area %, the content of the epoxy compound represented by formula (2) (peaks at 21.1 minutes and 22.1 minutes of A in Figure 4) is 6.0 area %.

[Example 3] 107 parts by weight of phenol resin (P3) synthesized in the same manner as in Example 1 except that toluene was set to 20 parts by weight, 230 parts by weight of epichlorohydrin and 60 parts by weight of dimethyl sulfoxide were placed in a reaction vessel, heated, stirred, and dissolved, and then 21 parts by weight of sodium hydroxide in the form of flakes were continuously added over 2 hours while maintaining the temperature at 45°C. After the addition of sodium hydroxide was completed, the reaction was further carried out at 45°C for 2 hours and at 70°C for 1 hour. Then, the by-product salt and dimethyl sulfoxide were removed by repeated water washing, and then the excess epichlorohydrin was removed from the oil layer under heating and reduced pressure, and 300 parts by weight of methyl isobutyl ketone was added to the residue and dissolved. The methyl isobutyl ketone solution was heated to 70°C, and 10 parts by weight of a 30% sodium hydroxide aqueous solution was added. After reacting for 1 hour, the reaction solution was repeatedly washed with water until the washing liquid became neutral. Then, methyl isobutyl ketone was removed from the oil layer under heating and reduced pressure, thereby obtaining 133 parts by weight of an epoxy resin mixture (EP2). The GPC chart of the epoxy resin mixture (EP2) is shown in Figure 2. The epoxy equivalent of the epoxy resin mixture (EP2) is 296 g/eq., the softening point is 69.8°C, and the ICI melt viscosity is 0.33 Pa·s (150°C). In the GC analysis, when the content of the epoxy resin in which n of the formula (1) is 1 (peaks at 24.9 minutes, 26.5 minutes, and 28.3 minutes in B in Figure 4) is set to 100 area %, the content of the epoxy compound represented by the formula (2) (peaks at 21.1 minutes and 22.1 minutes in A in Figure 4) is 3.5 area %.

[Synthesis Example 1] 107 parts by weight of phenol resin (P2) synthesized in the same manner as in Example 1 except that toluene was set to 0 parts by weight, 230 parts by weight of epichlorohydrin and 60 parts by weight of dimethyl sulfoxide were placed in a reaction vessel, heated, stirred, and dissolved, and then the temperature was maintained at 45°C, and 21 parts by weight of sodium hydroxide in the form of flakes were continuously added over 2 hours. After the addition of sodium hydroxide was completed, the reaction was further carried out at 45°C for 2 hours and at 70°C for 1 hour. Subsequently, water washing was repeated to remove by-product salts and dimethyl sulfoxide, and excess epichlorohydrin was distilled off from the oil layer under heating and reduced pressure, and 300 parts by weight of methyl isobutyl ketone was added to the residue and dissolved. The methyl isobutyl ketone solution was heated to 70°C, 10 parts by weight of a 30% aqueous sodium hydroxide solution was added, and after reacting for 1 hour, the reaction solution was repeatedly washed with water until the washing solution became neutral. Then, methyl isobutyl ketone was distilled off from the oil layer under heating and reduced pressure to obtain 135 parts by weight of epoxy resin (EP3). The GPC chart of epoxy resin (EP3) is shown in Figure 3. The epoxy equivalent of epoxy resin (EP3) is 288 g/eq., the softening point is 68°C, and the ICI melt viscosity is 0.30 Pa·s (150°C). In the GC analysis, the epoxy compound represented by the formula (2) is below the detection limit (peaks around 21.1 minutes and 22.1 minutes of C in Figure 4).

[Example 4, Example 5, Comparative Example 1] Epoxy resin mixture (EP1, EP2) and epoxy resin (EP3) were used as the main agent, phenol novolac (abbreviation: PN, hydroxyl equivalent 103 g/eq.) was used as a curing agent, and triphenylphosphine (abbreviation: TPP) was used as a curing accelerator. The mixture was mixed in the weight ratio shown in the formulation composition of Table 1, and the mixture was kneaded and tableted using a double roll. Then, a resin molded body was prepared by transfer molding, and the curing was performed under the curing conditions of 160°C for 2 hours and then 180°C for 6 hours.

The physical property values were measured under the following conditions. •Dynamic thermomechanical analyzer (DMA) analysis Manufacturer: TA Instruments Device: DMAQ800 Measurement mode: tensile Heating rate: 2℃/min. Measurement temperature range: 25℃～350℃ Measurement frequency: 10 Hz The temperature at which the tanδ value becomes the maximum is set as Tg. •Three-point bending test Manufacturer: A & D Co., Ltd. Equipment: RTG-1310 Test speed: 3 mm/min Distance between pivot points: 64 mm •Water absorption Heat a 5 cm diameter × 4 mm thick disc-shaped test piece at 100°C for 24 hours, measure the weight, and boil the test piece in 100°C water for 24 hours and measure the weight again. Calculate the weight increase rate (%) based on these weights.

[Table 1] Deployment composition Embodiment 3 Embodiment 4 Comparison Example 1 EP1 100 EP2 100 EP3 100 PN 33 35 36 TPP 1 1 1 Physical properties Heat resistance (DMA, Tg) ℃ 156 164 165 30℃ elastic modulus (bending test) GPa 2.8 2.9 2.7 Water absorption rate (100℃24 hours) % 1.06 1.06 1.17

According to the results in Table 1, it was confirmed that the heat resistance of Example 4, Example 5, and Comparative Example 1 all exceeded 150°C. In addition, it was confirmed that Example 4 and Example 5 had high elastic coefficients and excellent low water absorption. [Industrial Applicability]

The present invention is useful in insulating materials for electrical and electronic parts (high-reliability semiconductor sealing materials, etc.) and laminates (printed wiring boards, build-up substrates, etc.) or various composite materials, adhesives, coatings, etc., including FRP, and is particularly useful in laminates, and is also useful in insulating materials for metal-clad laminates, build-up substrates, flexible substrate materials, etc.

without

FIG1 is a gel permeation chromatography (GPC) chart showing Example 2. FIG2 is a GPC chart showing Example 3. FIG3 is a GPC chart showing Synthesis Example 1. FIG4A to FIG4C are gas chromatography (GC) charts showing Example 2, Example 3, and Synthesis Example 1.

Claims (4)

An epoxy resin mixture comprises an epoxy resin represented by the following formula (1) and an epoxy compound represented by the following formula (2). In a gas chromatography analysis of the epoxy resin mixture, when the content of the epoxy resin in the formula (1) where n is 1 is set to 100% by area, the content of the epoxy compound represented by the formula (2) is 1.0% by area to 10.0% by area.

In formula (1), n is a repeated number, and the average value of n represents a real number from 1 to 10.

An epoxy resin composition comprising the epoxy resin mixture as described in claim 1 and a hardener. A hardened material obtained by hardening the epoxy resin composition as described in claim 2. A method for producing an epoxy resin mixture, comprising: reacting epichlorohydrin with a phenol resin represented by the following formula (3) and a phenol compound represented by the following formula (4).

In formula (3), n is a repeated number, and the average value of n represents a real number from 1 to 10.