Epoxy resin mixture, epoxy resin composition and cured product of same

Abstract

The present invention provides: an epoxy resin mixture which has excellent mechanical strength and toughness at room temperature and in a high-temperature region; an epoxy resin composition; and a cured product thereof. The epoxy resin mixture contains an epoxy resin represented by formula (1), and has a sulfur content of 15-400ppm according to the combustion method. (In formula (1), n represents the number of repetitions and is a real number which is 1-20.)

Description

Epoxy resin mixture, epoxy resin composition and cured product thereof

[0001] The present invention relates to an epoxy resin mixture and an epoxy resin composition which are useful for applications such as insulating materials for electric and electronic components (e.g., highly reliable semiconductor encapsulating materials), laminates (e.g., printed wiring boards, build-up boards), and various composite materials including FRP (fiber reinforced plastics), adhesives, paints, etc., and particularly useful for applications such as laminates, metal foil-clad laminates, insulating materials for build-up boards, and flexible board materials.

[0002] Epoxy resins are widely used in fields such as electrical and electronic parts, structural materials, adhesives, and paints because of their workability and the excellent electrical properties, heat resistance, adhesiveness, and water absorption resistance of their cured products.

[0003] Carbon fiber reinforced composite materials (CFRP), which are made by impregnating reinforcing fibers with an epoxy resin and a curing agent as a matrix resin and then curing them, can be endowed with properties such as light weight and high strength. In recent years, they have been widely used in a variety of applications, including aircraft structural members, wind turbine blades, automobile exterior panels, and computer applications such as IC trays and laptop computer housings, and demand for them is increasing.

[0004] Cured thermosetting resins, such as epoxy resins, used as matrix resins for CFRP and other materials are generally brittle, and high mechanical strength is required at room temperature and at high temperatures when used as structural materials for aerospace applications, vehicles, and other applications. To compensate for the low flexural strength, toughness, adhesiveness, and other properties of thermosetting resins, a widely known method involves adding a highly tough thermoplastic resin to the thermosetting resin matrix (see Patent Documents 1 to 3). Specifically, the flexural strength and toughness of prepregs are improved by combining particles of thermoplastic resins such as polyethersulfone, polyetherimide, and polyamide with the thermosetting resin matrix resin.

[0005] However, thermoplastic resins such as polyethersulfone, polyetherimide, and polyamide are highly polar, and there is a possibility that phase separation may occur when mixed with epoxy resin or after prepreg production, which may result in the target strength and toughness not being achieved.

[0006] In the semiconductor industry, in addition to increasing functionality and performance, the development of package substrates required for mounting chips is also progressing, resulting in thinner substrates. As package substrates become thinner, toughness is becoming increasingly important in addition to properties such as heat resistance and dielectric properties. Multi-layer laminates use a variety of materials with different linear expansion coefficients, and in recent years, instead of the traditional substrates with a strong core, there has been an increase in substrates with no core or very thin cores. These substrates are unable to withstand the various forces applied to the interlayer materials, resulting in problems such as cracks in the substrates when subjected to thermal or mechanical shock.

[0007] JP 60-243113 A JP 09-100358 A JP 2013-155330 A JP 2017-008177 A

[0008] Biphenyl aralkyl type epoxy resins are generally known to have excellent flame retardancy and toughness, and are particularly used as semiconductor encapsulants. However, in order to apply them to various applications, there is a need to respond to the recent increasing demand for toughness, as mentioned above.

[0009] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an epoxy resin mixture, an epoxy resin composition, and a cured product thereof that exhibit excellent mechanical strength and toughness at room temperature and in high temperature ranges.

[0010] That is, the present invention provides the following [1] to [4]. In this application, "(Numerical value 1) to (Numerical value 2)" indicates that the upper and lower limits are included. [1] An epoxy resin mixture containing an epoxy resin represented by the following formula (1), and having a sulfur content of 15 ppm to 400 ppm as measured by a combustion method:

[0011]

[0012] (In formula (1), n ​​is the number of repeating units and represents a real number from 1 to 20.) [2] An epoxy resin mixture obtained by reacting a phenolic resin represented by the following formula (2), epichlorohydrin, and a sulfur-containing compound:

[0013]

[0014] (In formula (2), n is the number of repeating units and represents a real number from 1 to 20.) [3] An epoxy resin composition containing the epoxy resin mixture described in the preceding item [1] or [2] and a curing agent. [4] A cured product obtained by curing the epoxy resin composition described in the preceding item [3].

[0015] According to the present invention, it is possible to provide an epoxy resin mixture, an epoxy resin composition, and a cured product thereof, which have excellent mechanical strength and toughness at room temperature and at high temperatures, and which are therefore useful for circuit boards such as package substrates, FRP, etc.

[0016] 3 shows the stress-strain diagram of a three-point bending test at 30° C. 4 shows the stress-strain diagram of a three-point bending test at 120° C.

[0017] The epoxy resin mixture of the present invention contains an epoxy resin represented by the following formula (1), and has a sulfur content of 15 ppm to 400 ppm as determined by a combustion method.

[0018]

[0019] (In formula (1), n ​​is the number of repetitions and represents a real number from 1 to 20.)

[0020] In the present invention, the value of n in the formula (1) can be determined by gel permeation chromatography (GPC, detector: RI). n is usually a real number between 1 and 20, but is preferably between 1 and 10, and more preferably between 1 and 5. When n exceeds 20, the molecular weight increases, resulting in high viscosity and poor processability. The average value of n can be calculated from the number-average molecular weight determined by gel permeation chromatography (GPC, detector: RI) or the area ratio of each separated peak. An average n of less than 1 indicates a high content of monofunctional epoxy resins, which not only affects curability and the heat resistance of the cured product, but also hinders the formation of crosslinked structures, resulting in reduced toughness. On the other hand, when n exceeds 20, the solvent solubility of the epoxy resin deteriorates, the viscosity increases, and the softening point rises significantly, making handling difficult. In the present invention, an average n of 1.3 to 3.5 is particularly preferred, which is also preferable in terms of flowability, heat resistance, and curability. In this case, the area ratio of n=1 is 15 to 50 area%, and particularly preferably 17 to 45 area%. If the area of ​​n=1 is too small, problems arise in terms of fluidity, and solubility in solvents deteriorates, making handling a problem. If it is 50 area% or more, crystallinity increases, which can make handling a problem. Therefore, an area ratio of n=1 of 15 to 50 area% provides an excellent balance.

[0021] The epoxy equivalent of the epoxy resin mixture of the present invention is preferably in the range of 260 g / eq. or more but less than 400 g / eq., more preferably 265 g / eq. or more but less than 350 g / eq., particularly preferably 270 g / eq. or more but less than 320 g / eq., and most preferably 280 g / eq. or more but less than 300 g / eq. If the epoxy equivalent is less than 260 g / eq., impurities derived from epichlorohydrin, which introduces or replicates excessive epoxy groups, remain, preventing crosslinking during curing and resulting in reduced heat resistance and toughness. Furthermore, if the epoxy equivalent is 400 g / eq. or more, the epoxy groups do not close cleanly, resulting in an increase in chlorine, which adversely affects corrosion. Alternatively, the purified epoxy resin may unnecessarily react with the raw materials in the epoxidation process, resulting in a large molecular weight and reduced heat resistance, which is undesirable. When the epoxy equivalent is appropriate, the heat resistance of the cured product can be improved without causing a decrease in mechanical strength.

[0022] In the present invention, the epoxy equivalent is measured by the method described in JIS K-7236.

[0023] The softening point of the epoxy resin mixture of the present invention is preferably in the range of 60 to 100° C., more preferably 47 to 90° C. When the softening point is in the above range, the resins do not block with each other at room temperature, resulting in excellent handleability.

[0024] The epoxy resin mixture of the present invention has a sulfur content of 15 ppm to 400 ppm, preferably 20 to 250 ppm, particularly preferably 30 to 225 ppm, and most preferably 40 to 200 ppm, as determined by a combustion method. The sulfur is introduced in the form of an aromatic ring or an addition to the epoxy. If the sulfur content is less than 15 ppm, high strength and toughness cannot be achieved, and if it exceeds 400 ppm, it is not preferred because it may cause corrosion of metal joints (wire bonding parts) when used as a semiconductor encapsulant, etc. Japanese Patent Application Laid-Open No. 2017-008177 discloses that SO ３It is also known from known literature that when used in electronic materials, the sulfur content is preferably about 400 ppm or less in terms of sulfur. In other words, when the sulfur content is within the above range, the cured product of the epoxy resin mixture of the present invention can exhibit excellent mechanical strength and toughness at room temperature and at high temperatures, and will not cause any problems when used in electronic materials.

[0025] In the present invention, the sulfur content is determined by a combustion method, specifically under the following conditions: [Pyrolysis step] Equipment: Thermo SCIENTIFIC Combustion Ion Chromatography System (Pyrolysis conditions): Combustion temperature: 1000°C, kept for 15 minutes; Gas flow rate: Ar 200 ml / min O ２ 400 ml / min Sample 0.05 g (decomposition gas absorption liquid) Phosphate ion standard solution 1000 ppm 1 mL H ２ O ２ Dilute 0.05 mL of 30% with water to make 500 mL [Ion chromatography step of absorbed solution] Apparatus: Dionex Integration HPLC Guard column: Dionex Ionpac AS12A (4 x 50 mm) Column: Dionex Ion Pac AS12A (4 x 200 mm) Suppressor: Dionex ADRS 600 (4 mm) Eluent: Sodium carbonate / sodium bicarbonate mixture Detector: CD (electrical conductivity detector)

[0026] The epoxy resin mixture of the present invention preferably has an inorganic sulfur component (sulfide ion) content of 10 ppm or less. If the sulfur remains as ions rather than as organic sulfur as described above, electrical devices obtained using the epoxy resin mixture are at risk of corrosion and reduced reliability. A content of 5 ppm or less is more preferred, and 2 ppm or less is most preferred. The ion content can be measured by placing the resin in pure water, extracting for 20 hours at a temperature above the softening point, and measuring the resulting extract by ion chromatography.

[0027] A cured product obtained by curing the epoxy resin mixture of the present invention has excellent mechanical strength and toughness at room temperature and at high temperatures. An index of mechanical strength is the stress (MPa) in a three-point bending test, and an index of toughness is the strain (%) in a three-point bending test. The stress in a three-point bending test at room temperature (30°C) is preferably 90 MPa or more, more preferably 95 MPa or more, and particularly preferably 100 MPa or more. The strain in a three-point bending test at 30°C is preferably 4.0% or more, and more preferably 6.0% or more. The stress in a three-point bending test at a high temperature (120°C) is preferably 60 MPa or more, and more preferably 65 MPa or more. The strain in a three-point bending test at 120°C is preferably 5.0% or more, more preferably 6.0% or more, and particularly preferably 8.0% or more. When a cured thermosetting resin used in a matrix resin such as CFRP is applied to a structural material for aerospace or vehicles, high mechanical strength is required at both room temperature and high temperatures. If the mechanical strength is low, the material may break when a strong force is applied. Therefore, a material with as high mechanical strength as possible is preferable. Furthermore, when a thin substrate such as a packaging substrate is subjected to mechanical shock, the substrate may not be able to withstand the shock and may break. Therefore, a material with as high toughness as possible is also preferable.

[0028] The epoxy resin mixture of the present invention can be produced by epoxidizing a phenolic resin represented by the following formula (2) with epichlorohydrin. In this process, a sulfur-containing compound, which will be described later, is epoxidized simultaneously to produce a compound containing a sulfur atom in the molecule.

[0029]

[0030] (In formula (2), n is the number of repetitions and represents a real number from 1 to 20.)

[0031] In the formula (2), the preferred range of n is the same as in the formula (1).

[0032] Methods for synthesizing the phenolic resin represented by formula (2) include, but are not limited to, the reaction of phenol with a biphenyl compound having a benzylmethylene group, such as bischloromethylbiphenyl, bismethoxymethylbiphenyl, or bishydroxymethylbiphenyl. The use of 4,4'-bischloromethylbiphenyl or 4,4'-bismethoxymethylbiphenyl with a purity of 90% or higher is particularly preferred from an industrial perspective. The amount of biphenyl compound used in this case is typically 1 to 9 moles, preferably 1 to 6 moles, per 10 moles of phenol. Specific synthesis methods include, but are not limited to, those described in JP-A No. 2003-301031, Japanese Patent No. 3,122,834, Japanese Patent No. 5,686,770, and Japanese Patent No. 3,934,829.

[0033] Next, the reaction for obtaining the epoxy resin mixture of the present invention will be described. The epoxy resin mixture of the present invention can be obtained by reacting the phenolic resin represented by the formula (2) with epichlorohydrin and a sulfur-containing compound.

[0034] Epichlorohydrin is readily available on the market. The amount of epichlorohydrin used is usually 3.0 to 10 mol, preferably 3.5 to 8.0 mol, more preferably 4.0 to 7.0 mol per mol of hydroxyl groups in the raw material phenolic resin.

[0035] In the above reaction, it is preferable to carry out the reaction in the presence of an alcohol such as methanol, ethanol, or isopropyl alcohol, or an aprotic polar solvent such as dimethyl sulfone, dimethyl sulfoxide, tetrahydrofuran, or dioxane, in order to advance the reaction. When an alcohol is used, the amount used is usually 2 to 50% by weight, preferably 4 to 20% by weight, based on the amount of epihalohydrin used. When an aprotic polar solvent is used, the amount used is usually 5 to 100% by weight, preferably 10 to 80% by weight, based on the amount of epihalohydrin used.

[0036] In the above reaction, an alkali metal hydroxide can be used as a catalyst to promote the epoxidation step. Usable alkali metal hydroxides include sodium hydroxide and potassium hydroxide. While solids or aqueous solutions thereof may be used, the use of flake-shaped solids is particularly preferred in the present invention for solubility and ease of handling. The amount of alkali metal hydroxide used is typically 0.90 to 1.50 moles per mole of hydroxyl groups in the raw phenolic resin. 1.01 to 1.35 moles is particularly preferred. If the amount is less than 0.90 moles, the number of compounds that do not undergo complete epoxidation increases, and the increased chlorine content can easily lead to corrosion. Furthermore, if the amount exceeds 1.5 moles, hydroxide ions react with the resulting epoxy groups, facilitating the formation of α-glycol structures, resulting in a decrease in crosslink density; therefore, the above range is preferred.

[0037] Furthermore, in order to promote the reaction, a quaternary ammonium salt such as tetramethylammonium chloride, tetramethylammonium bromide, trimethylbenzylammonium chloride, or the like may be added as a catalyst. The amount of the quaternary ammonium salt used is usually preferably 0.0009 to 0.15 mol per mol of hydroxyl groups in the raw material phenolic resin.

[0038] In the present invention, sulfur is introduced into the molecule by simultaneously reacting a sulfur-containing compound during the epoxidation reaction. The sulfur-containing compound is not particularly limited as long as it contains sulfur in its structure, but examples include thioether compounds and disulfide compounds. Specifically, an epoxy resin mixture containing a sulfur-containing compound can be obtained by adding a sulfur-containing compound such as a thioether compound having 1 to 10 carbon atoms, such as dimethyl sulfide, diallyl sulfide, diethyl sulfide, or methyl phenyl sulfide; a disulfide compound having 1 to 10 carbon atoms, such as dimethyl disulfide, allyl disulfide, dibutyl disulfide, or diphenyl disulfide; or a trisulfide having 1 to 10 carbon atoms, such as dimethyl trisulfide or dipropyl trisulfide. The sulfur-containing compound preferably has 2 to 4 carbon atoms, with dimethyl sulfide and dimethyl disulfide being particularly preferred. This is because the low molecular weight of the compound makes it easy to remove unreacted sulfide compounds in subsequent processes. The amount of these sulfur compounds added is usually preferably 0.1 to 50 parts by weight, more preferably 0.5 to 40 parts by weight, and particularly preferably 1 to 30 parts by weight, per 1,000 parts by weight of the raw material phenolic resin. If the amount of sulfur-containing compound added is less than the above range, the content of sulfur-containing compound in the epoxy resin mixture after completion of the reaction step will be low, and excellent mechanical strength and toughness will not be obtained. On the other hand, if the content of sulfur-containing compound is greater than the above range, the content of sulfur-containing compound in the epoxy resin mixture after completion of the reaction step will be too high, which will cause corrosion of metal wiring in high-temperature regions as described above. If the amount of sulfur compound added is within the above range, there will be little effect on corrosion of metal wiring, and excellent mechanical strength and toughness can be obtained.

[0039] The epoxidation reaction temperature is typically 30 to 90°C, preferably 35 to 80°C. The reaction time is typically 0.5 to 10 hours, preferably 1 to 8 hours. After the reaction is complete, the reaction product is washed with water, or without washing, and the epihalohydrin and solvent are removed under reduced pressure with heating to obtain the epoxy resin represented by formula (2). Alternatively, to obtain an epoxy resin with a low hydrolyzable halogen content, the recovered epoxy resin can be dissolved in a solvent such as toluene or methyl isobutyl ketone, and an aqueous solution of an alkali metal hydroxide such as sodium hydroxide or potassium hydroxide is added to the reaction mixture to ensure ring closure. In this case, the amount of alkali metal hydroxide used is typically 0.01 to 0.3 mol, preferably 0.05 to 0.2 mol, per mol of hydroxyl groups in the phenolic compound used for glycidylation. The reaction temperature is typically 50 to 120°C, and the reaction time is typically 0.5 to 2 hours.

[0040] After the reaction is complete, the salt formed is removed by filtration, washing with water, etc., and the solvent is then distilled off under heating and reduced pressure to obtain the epoxy resin mixture of the present invention.

[0041] The epoxy resin composition of the present invention contains a curing agent, such as a phenol-based curing agent, an acid anhydride-based curing agent, an amide-based curing agent, or an amine-based curing agent.

[0042] In the epoxy resin composition of the present invention, a phenolic resin having a repeating unit is particularly preferred as a phenolic curing agent, since it can achieve a good balance between heat resistance and thermal stability of the cured product. Examples of phenolic curing agents include phenolic resins such as phenol novolac resin, cresol novolac resin, and phenol aralkyl resin; polyhydric phenols (bisphenol A, bisphenol F, bisphenol S, fluorene bisphenol, terpene diphenol, 4,4'-dihydroxybiphenyl, 2,2'-dihydroxybiphenyl, 3,3',5,5'-tetramethyl-(1,1'-biphenyl)-4,4'-diol, hydroquinone, resorcinol, naphthalenediol, tris-(4-hydroxyphenyl)methane, and 1,1,2,2-tetrakis(4-hydroxyphenyl)ethane, etc.); phenols (for example, phenol, alkyl-substituted phenol, naphthol, alkyl-substituted naphthol, dihydroxybenzene, and dihydroxynaphthalene, etc.); and aldehydes (formaldehyde, acetaldehyde, benzaldehyde, etc.). phenolic resins obtained by condensation of the above phenols with 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.); modified products of the above phenols and / or the above phenolic resins; and halogenated phenols such as tetrabromobisphenol A and brominated phenolic resins.

[0043] Examples of the acid anhydride curing agent include phthalic anhydride, trimellitic anhydride, pyromellitic anhydride, maleic anhydride, tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, methylnadic anhydride, hexahydrophthalic anhydride, and methylhexahydrophthalic anhydride.

[0044] Examples of the amide-based curing agent include dicyandiamide, or a polyamide resin synthesized from a dimer of linolenic acid and ethylenediamine.

[0045] Examples of amine-based curing agents include 3,3'-diaminodiphenyl sulfone (3,3'-DDS), 4,4'-diaminodiphenyl sulfone (4,4'-DDS), diaminodiphenylmethane (DDM), 3,3'-diisopropyl-4,4'-diaminodiphenylmethane, 3,3'-di-t-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-t-butyl-5,5'-dimethyl-4,4'-diaminodiphenylmethane, 3,3',5,5'-tetraethyl-4,4'-diaminodiphenylmethane, 3,3'-diisopropyl-5,5'-diethyl-4,4' -diaminodiphenylmethane, 3,3'-di-t-butyl-5,5'-diethyl-4,4'-diaminodiphenylmethane, 3,3',5,5'-tetraisopropyl-4,4'-diaminodiphenylmethane, 3,3'-di-t-butyl-5,5'-diisopropyl-4,4'-diaminodiphenylmethane, 3,3',5,5'-tetra-t-butyl-4,4'-diaminodiphenylmethane, diaminodiphenyl ether (DADPE), bisaniline, benzyldimethylaniline, 2-(dimethylaminomethyl)phenol (DMP-10), 2,4,6-tris(dimethylaminomethyl)phenol (DMP-30), 2-ethylhexanoate ester of 2,4,6-tris(dimethylaminomethyl)phenol, and the like can be used. Other examples include aniline novolak, orthoethylaniline novolak, aniline resins obtained by reacting aniline with xylylene chloride, and aniline resins obtained by polycondensation of aniline with substituted biphenyls (4,4'-bis(chloromethyl)-1,1'-biphenyl, 4,4'-bis(methoxymethyl)-1,1'-biphenyl, etc.) or substituted phenyls (1,4-bis(chloromethyl)benzene, 1,4-bis(methoxymethyl)benzene, 1,4-bis(hydroxymethyl)benzene, etc.).

[0046] In the epoxy resin composition of the present invention, the amount of curing agent used is preferably 0.7 to 1.2 equivalents per equivalent of epoxy groups in the epoxy resin. If the amount is less than 0.7 equivalents or more than 1.2 equivalents per equivalent of epoxy groups, curing may be incomplete and good cured physical properties may not be obtained.

[0047] Furthermore, if necessary, a curing accelerator may be blended into the epoxy resin composition of the present invention. The use of a curing accelerator can also adjust the gelation time. Examples of curing accelerators that can be used include imidazoles such as 2-methylimidazole, 2-ethylimidazole, 2-phenylimidazole, and 2-ethyl-4-methylimidazole; tertiary amines such as 2-(dimethylaminomethyl)phenol, triethylenediamine, triethanolamine, and 1,8-diazabicyclo(5.4.0)undecene-7; phosphines and phosphonium compounds such as triphenylphosphine, tri(toluyl)phosphine, tetraphenylphosphonium bromide, and tetraphenylphosphonium tetraphenylborate; metal compounds such as tin octoate; tetra-substituted phosphonium tetra-substituted borates such as tetraphenylphosphonium tetraphenylborate and tetraphenylphosphonium ethyltriphenylborate; and tetraphenylboron salts such as 2-ethyl-4-methylimidazole tetraphenylborate and N-methylmorpholine tetraphenylborate. The curing accelerator is used as needed in an amount of 0.01 to 5.0 parts by weight per 100 parts by weight of the epoxy resin.

[0048] The epoxy resin composition of the present invention may contain other epoxy resins. 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 aldehyde, benzaldehyde, alkyl-substituted benzaldehyde, hydroxybenzaldehyde, naphthaldehyde, Polycondensates of phenols and various diene compounds (dicyclopentadiene, terpenes, vinylcyclohexene, norbornadiene, vinylnorbornene, tetrahydroindene, divinylbenzene, divinylbiphenyl, diisopropenylbiphenyl, butadiene, isoprene, etc.), polymers of phenols and ketones (acetone, methyl ethyl ketone, methyl isobutyl ketone, acetophenone, benzophenone, etc.), phenolic resins obtained by polycondensation 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, 1,4-bis(hydroxymethyl)benzene, etc.); polycondensates of bisphenols and various aldehydes; glycidyl ether epoxy resins obtained by glycidylating alcohols, etc.; alicyclic epoxy resins typified by 4-vinyl-1-cyclohexene diepoxide and 3,4-epoxycyclohexylmethyl-3,4'-epoxycyclohexanecarboxylate, etc.; glycidylamine epoxy resins typified by tetraglycidyldiaminodiphenylmethane (TGDDM) and triglycidyl-p-aminophenol, etc.; glycidyl ester epoxy resins, etc., but are not limited to these, so long as they are commonly used epoxy resins.

[0049] Furthermore, inorganic fillers can be added to the epoxy resin composition of the present invention as needed. Examples of inorganic fillers include, but are not limited to, powders such as crystalline silica, fused silica, alumina, zircon, calcium silicate, calcium carbonate, silicon carbide, silicon nitride, boron nitride, zirconia, fosterite, steatite, spinel, titania, and talc, as well as spherical beads thereof. These fillers may be used alone or in combination of two or more. The amount of inorganic filler used varies depending on the application. For example, when used as a semiconductor sealant, the inorganic filler is preferably used in an amount of 20% by weight or more of the epoxy resin composition, more preferably 30% by weight or more, in terms of the heat resistance, moisture resistance, mechanical properties, and flame retardancy of the cured product of the epoxy resin composition. Furthermore, it is even more preferable to use the inorganic filler in an amount of 70 to 95% by weight, particularly to improve the linear expansion coefficient with the lead frame.

[0050] The epoxy resin composition of the present invention can be blended with a release agent to improve release from the mold during molding. Any of the conventionally known release agents can be used, including ester waxes such as carnauba wax and montan wax, fatty acids such as stearic acid and palmitic acid and their metal salts, and polyolefin waxes such as oxidized polyethylene and non-oxidized polyethylene. These may be used alone or in combination. The amount of these release agents blended is preferably 0.5 to 3% by weight of the total organic components. Less than this amount results in poor release from the mold, while more results in poor adhesion to lead frames and the like.

[0051] The epoxy resin composition of the present invention can contain a coupling agent to enhance adhesion between the inorganic filler and the resin component. Any conventionally known coupling agent can be used, including, for example, various alkoxysilane compounds such as vinylalkoxysilane, epoxyalkoxysilane, styrylalkoxysilane, methacryloxyalkoxysilane, acryloxyalkoxysilane, aminoalkoxysilane, mercaptoalkoxysilane, and isocyanatoalkoxysilane; alkoxytitanium compounds; and aluminum chelates. These can be used alone or in combination of two or more. The coupling agent can be added by first treating the surface of the inorganic filler with the coupling agent and then kneading it with the resin, or by mixing the coupling agent with the resin and then kneading the inorganic filler.

[0052] Furthermore, known additives can be blended into the epoxy resin composition of the present invention as needed. Specific examples of usable additives include polybutadiene and its modified products, modified acrylonitrile copolymers, polyphenylene ether, polystyrene, polyethylene, polyimide, fluororesin, maleimide compounds, cyanate ester compounds, silicone gel, silicone oil, and colorants such as carbon black, phthalocyanine blue, and phthalocyanine green.

[0053] The epoxy resin composition of the present invention can contain known maleimide compounds as needed. Specific examples of usable maleimide compounds include, but are not limited to, 4,4'-diphenylmethane bismaleimide, polyphenylmethane maleimide, m-phenylene bismaleimide, 2,2'-bis[4-(4-maleimidophenoxy)phenyl]propane, 3,3'-dimethyl-5,5'-diethyl-4,4'-diphenylmethane bismaleimide, 4-methyl-1,3-phenylene bismaleimide, 4,4'-diphenylether bismaleimide, 4,4'-diphenylsulfone bismaleimide, 1,3-bis(3-maleimidophenoxy)benzene, and 1,3-bis(4-maleimidophenoxy)benzene. These compounds may be used alone or in combination. When a maleimide compound is blended, a curing accelerator is blended as necessary. The above-mentioned curing accelerators, as well as radical polymerization initiators such as organic peroxides and azo compounds can be used.

[0054] The epoxy resin composition of the present invention can be obtained by uniformly mixing the above-mentioned components. The epoxy resin composition of the present invention can be easily cured by methods similar to those known in the art. For example, the epoxy resin and curing agent, as well as optional curing accelerators, inorganic fillers, mold release agents, silane coupling agents, and additives, can be thoroughly mixed until uniform using an extruder, kneader, rolls, or the like, to obtain the epoxy resin composition of the present invention. This can then be molded by melt casting, transfer molding, injection molding, compression molding, or the like, and further heated at 80 to 200°C for 2 to 10 hours to obtain a cured product.

[0055] The epoxy resin composition of the present invention may also contain a solvent, if necessary. The solvent-containing epoxy resin composition (epoxy resin varnish) is impregnated into a fibrous material (substrate) such as glass fiber, carbon fiber, polyester fiber, polyamide fiber, alumina fiber, or paper, and the resulting prepreg is heat-dried and hot-press molded to produce a cured product of the epoxy resin composition of the present invention. The solvent content of this epoxy resin composition is typically about 10 to 70% by weight, preferably about 15 to 70% by weight. Examples of the solvent include amide solvents such as γ-butyrolactones, N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, and N,N-dimethylimidazolidinone; sulfones such as tetramethylene sulfone; ether solvents such as diethylene glycol dimethyl ether, diethylene glycol diethyl ether, propylene glycol monomethyl ether, propylene glycol monomethyl ether acetate, and propylene glycol monobutyl ether, preferably mono- or di-lower (1 to 3 carbon atoms) alkyl ethers of lower (1 to 3 carbon atoms) alkylene glycols; ketone solvents such as methyl ethyl ketone and methyl isobutyl ketone, more preferably di-lower (1 to 3 carbon atoms) alkyl ketones in which the two alkyl groups may be the same or different; and aromatic solvents such as toluene and xylene. These may be used alone or in combination.

[0056] Furthermore, a sheet-like adhesive (the sheet of the present invention) can be obtained by applying the epoxy resin varnish to a release film, removing the solvent under heating, and then B-staging the varnish. This sheet-like adhesive can be used as an interlayer insulating layer in a multilayer substrate or the like.

[0057] The prepreg of the present invention can also be obtained by heating and melting the epoxy resin composition and / or resin sheet of the present invention to reduce its viscosity and impregnating the composition into a fiber substrate.

[0058] Alternatively, the prepreg of the present invention can be obtained by impregnating a fiber substrate with a varnish-like epoxy resin composition and drying it by heating. The prepreg is cut into a desired shape, laminated, and then the laminate is heat-cured while applying pressure by press molding, autoclave molding, sheet winding, or other methods, to obtain the FRP of the present invention. Copper foil or an organic film can also be laminated during the lamination of the prepreg.

[0059] Furthermore, the FRP of the present invention can be obtained by molding using known methods other than the above-mentioned methods. For example, resin transfer molding (RTM) can be used, in which a carbon fiber substrate (usually a carbon fiber fabric) is cut, laminated, and shaped to produce a preform (a preform before being impregnated with resin), the preform is placed in a mold, the mold is closed, resin is injected to impregnate the preform, and the resin is cured, and the mold is then opened to remove the molded product. Also usable are types of RTM methods, such as the VaRTM method, the SCRIMP (Seeman's Composite Resin Infusion Molding Process), and the CAPRI (Controlled Atmospheric Pressure Resin Infusion) method, which is described in JP-A-2005-527410, in which a resin supply tank is evacuated to a pressure lower than atmospheric pressure, cyclic compression is used, and the net molding pressure is controlled to more appropriately control the resin injection process, particularly the VaRTM method.

[0060] Furthermore, a film stacking method in which a fiber substrate is sandwiched between resin sheets (films), a method in which powdered resin is attached to a reinforcing fiber substrate to improve impregnation, a molding method in which a fluidized bed or fluid slurry method is used in the process of mixing resin into a fiber substrate (Powder Impregnated Yarn), and a method in which resin fibers are mixed into a fiber substrate can also be used.

[0061] Examples of carbon fibers include acrylic, pitch, and rayon carbon fibers, and among these, acrylic carbon fibers, which have high tensile strength, are preferably used. The carbon fiber may be in the form of twisted yarn, untwisted yarn, or non-twisted yarn, but untwisted yarn or non-twisted yarn is preferred because it provides a good balance between the formability and strength properties of the fiber-reinforced composite material.

[0062] The cured product obtained by the present invention can be used for various purposes other than the above-mentioned applications such as substrates and CFRP, etc. Specifically, these include general applications in which thermosetting resins such as epoxy resins are used, such as adhesives, paints, coating agents, molding materials (including sheets, films, FRP, etc.), insulating materials (including electric wire coatings, etc.), sealants, and additives for other resins, etc.

[0063] Examples of adhesives include adhesives for civil engineering, construction, automobiles, general office use, and medical use, as well as adhesives for electronic materials. Among these, adhesives for electronic materials include interlayer adhesives for multilayer substrates such as build-up substrates, die bonding agents, semiconductor adhesives such as underfills, underfills for reinforcing BGAs, and mounting adhesives such as anisotropic conductive films (ACFs) and anisotropic conductive pastes (ACPs).

[0064] Examples of the sealant include potting, dipping, and transfer mold sealing for capacitors, transistors, diodes, light-emitting diodes, ICs, and LSIs; potting sealing for COB, COF, TAB, and the like for ICs and LSIs; underfill for flip chips; and sealing (including reinforcing underfill) when mounting IC packages such as QFP, BGA, and CSP.

[0065] The present invention will be explained in more detail below with reference to examples. The materials, processing details, processing procedures, etc. shown below can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the specific examples shown below.

[0066] Various analytical methods were carried out under the following conditions. Epoxy equivalent: Measured according to the method described in JIS K-7236, and expressed in g / eq. Softening point: Measured according to the method conforming to JIS K-7234, and expressed in °C. Melt viscosity: Measured by the ICI melt viscosity (150°C) cone-plate method, and expressed in Pa s.

[0067] GPC (Gel Per Emission Chromatography) Analysis Manufacturer: Waters Apparatus: Alliance Waters e2695 Column: Guard column SHODEX GPC KF-601 (2 columns), KF-602 KF-602.5, KF-603 Flow rate: 1.23 ml / min. Column temperature: 25°C Solvent used: THF (tetrahydrofuran) Detector: RI (differential refractometer)

[0068] Sulfur content analysis (combustion method) [Pyrolysis process] Equipment: Thermo SCIENTIFIC Combustion Ion Chromatography System (Pyrolysis conditions): Combustion temperature: 1000°C, kept for 15 minutes Gas flow rate: Ar 200 ml / min O ２ 400 ml / min Sample 0.05 g (decomposition gas absorption liquid) Phosphate ion standard solution 1000 ppm 1 mL H ２ O ２ Dilute 0.05 mL of 30% with water to make 500 mL [Ion chromatography step of absorbed solution] Apparatus: Dionex Integration HPLC Guard column: Dionex Ionpac AS12A (4 x 50 mm) Column: Dionex Ion Pac AS12A (4 x 200 mm) Suppressor: Dionex ADRS 600 (4 mm) Eluent: Sodium carbonate / sodium bicarbonate mixture Detector: CD (electrical conductivity detector)

[0069] Ion chromatography of extracted water 8 g of sample was immersed in pure water and extracted at 95°C for 20 hours, and the extracted water was measured by ion chromatography. Apparatus: Dionex Integration HPLC Guard column: Dionex Ionpac AS12A (4 x 50 mm) Column: Dionex Ion Pac AS12A (4 x 200 mm) Suppressor: Dionex ADRS 600 (4 mm) Eluent: Sodium carbonate / sodium bicarbonate mixture Detector: CD (electrical conductivity detector)

[0070] Synthesis Example 1: A flask equipped with a stirrer, reflux condenser, and stirring device was charged with 333 parts by weight of phenol and 0.5 parts of concentrated hydrochloric acid. After stirring and dissolution, 240 parts by weight of 4,4'-bischloromethylbiphenyl was continuously added over 4 hours while heating and blowing in nitrogen to maintain the temperature at 70°C. After the addition was completed, the reaction was continued for an additional 2 hours at the same temperature and then for an additional 2 hours at 80°C. After the reaction was completed, excess phenol was distilled off under heating and reduced pressure to obtain 304 parts by weight of phenolic resin (P1). The resulting phenolic resin had a residual phenol content of 0.15%, a softening point of 133°C, and an ICI melt viscosity at 150°C of 0.12 Pa s. Analysis by gel permeation chromatography confirmed that n=1 was 40.5 area % (UV-254 nm).

[0071] Synthesis Example 2: A flask equipped with a stirrer, reflux condenser, and stirring device was charged with 693 parts by weight of phenol, 0.006 parts by weight of paratoluenesulfonic acid, and 75 parts by weight of sodium carbonate. After stirring and dissolution, 799 parts by weight of 4,4'-bischloromethylbiphenyl was continuously added over 4 hours while heating and blowing in nitrogen to maintain the temperature at 105°C. After the addition was completed, the reaction was continued for an additional 1.5 hours at the same temperature. After the reaction was completed, 11.7 parts by weight of sodium tripolyphosphate was added and stirred for 30 minutes. After that, excess phenol was distilled off under reduced pressure with heating to obtain 1,080 parts by weight of phenolic resin (P2). The resulting phenolic resin had a residual phenol content of 0.01%, a softening point of 86.2°C, and an ICI melt viscosity at 150°C of 0.53 Pa·s. Analysis by gel permeation chromatography confirmed that n=1 was 24.5 area % (UV-254 nm).

[0072] Example 1: 200 parts by weight of the phenolic resin (P1) obtained in Synthesis Example 1 were charged into a reaction vessel with 475 parts by weight of epichlorohydrin, 143 parts by weight of dimethyl sulfoxide, 0.76 parts by weight of dimethyl sulfide, and 0.06 parts by weight of dimethyl disulfide. After stirring and dissolving under a nitrogen atmosphere, 42 parts by weight of flaky sodium hydroxide were continuously added over 2 hours while maintaining the temperature at 45°C. After completion of the sodium hydroxide addition, the reaction was further carried out at 45°C for 2 hours and then at 70°C for 1 hour. After repeated water washing to remove by-product salts, excess epichlorohydrin and the like were distilled from the oil layer under heating and reduced pressure, and 512 parts by weight of methyl isobutyl ketone was added to the residue and dissolved. This methyl isobutyl ketone solution was heated to 70°C, and 20 parts by weight of a 30% aqueous sodium hydroxide solution was added. The reaction was allowed to proceed for 1 hour, after which the reaction solution was repeatedly washed with water until the washings became neutral. Next, 220 parts by weight of epoxy resin mixture (EP1) was obtained by distilling off methyl isobutyl ketone from the oil layer under heating and reduced pressure. The resulting epoxy resin mixture had an epoxy equivalent of 276 g / eq., a softening point of 57.9°C, and an ICI melt viscosity of 0.09 Pa s (150°C). The sulfur content in epoxy resin (EP1) was confirmed to be 24 ppm by quantitative analysis using a combustion method. Analysis by gel permeation chromatography confirmed that n=1 was 32.93 area % (UV-254 nm). Furthermore, ion chromatography of the extracted water (extracted at 95°C) confirmed that the quantitative value of sulfide ions was <1 ppm.

[0073] Example 2: 200 parts by weight of the phenolic resin (P2) obtained in Synthesis Example 2 were charged into a reaction vessel with 381 parts by weight of epichlorohydrin, 95.3 parts by weight of dimethyl sulfoxide, 0.65 parts by weight of dimethyl sulfide, and 0.78 parts by weight of dimethyl disulfide. The mixture was stirred and dissolved under a nitrogen atmosphere. After dissolving, 34.6 parts by weight of flaky sodium hydroxide was continuously added over 2 hours while maintaining the temperature at 45°C. After the sodium hydroxide addition was completed, the reaction was further carried out at 45°C for 2 hours and then at 70°C for 1 hour. After repeated water washing to remove by-product salts, excess epichlorohydrin and the like were distilled from the oil layer under heating and reduced pressure. 444 parts by weight of methyl isobutyl ketone was added to the residue and dissolved. This methyl isobutyl ketone solution was heated to 70°C, and 8.2 parts by weight of a 30% aqueous sodium hydroxide solution was added. The reaction was allowed to proceed for 1 hour, after which the reaction solution was repeatedly washed with water until the washings became neutral. Next, methyl isobutyl ketone was distilled off from the oil layer under heating and reduced pressure, yielding 222 parts by weight of an epoxy resin mixture (EP2). The resulting epoxy resin mixture had an epoxy equivalent of 292 g / eq., a softening point of 69°C, and an ICI melt viscosity of 0.31 Pa s (150°C). The sulfur content in the epoxy resin (EP2) was determined to be 52 ppm by quantitative combustion analysis. Analysis by gel permeation chromatography confirmed that n=1 was 22.1 area % (UV-254 nm). Furthermore, ion chromatography of the extracted water (extracted at 95°C) confirmed that the quantitative value of sulfide ions was <1 ppm.

[0074] Example 3: 200 parts by weight of the phenolic resin (P2) obtained in Synthesis Example 2 were charged into a reaction vessel with 381 parts by weight of epichlorohydrin, 95.3 parts by weight of dimethyl sulfoxide, 0.59 parts by weight of dimethyl sulfide, and 0.04 parts by weight of dimethyl disulfide. After stirring and dissolving under a nitrogen atmosphere, 34.6 parts by weight of flaky sodium hydroxide were continuously added over 2 hours while maintaining the temperature at 45°C. After completion of the sodium hydroxide addition, the reaction was further carried out at 45°C for 2 hours and then at 70°C for 1 hour. After repeated water washing to remove by-product salts, excess epichlorohydrin and the like were distilled from the oil layer under heating and reduced pressure, and 444 parts by weight of methyl isobutyl ketone was added to the residue and dissolved. This methyl isobutyl ketone solution was heated to 70°C, and 8.2 parts by weight of a 30% aqueous sodium hydroxide solution was added. The reaction was allowed to proceed for 1 hour, after which the reaction solution was repeatedly washed with water until the washings became neutral. Next, 215 parts by weight of epoxy resin (EP3) was obtained by distilling off methyl isobutyl ketone from the oil layer under heating and reduced pressure. The epoxy equivalent of the obtained epoxy resin was 296 g / eq., softening point 69.8°C, and ICI melt viscosity 0.33 Pa s (150°C). The sulfur content in epoxy resin (EP3) was 19 ppm as determined by combustion quantification. Analysis by gel permeation chromatography confirmed that n=1 was 20.2 area % (UV-254 nm). Furthermore, ion chromatography of the extracted water (extracted at 95°C) confirmed that the quantitative value of sulfide ions was <1 ppm.

[0075] Comparative Example 1: 218 parts by weight of epoxy resin (EP4) were obtained by synthesis in the same manner as in Example 2, except that the amounts of dimethyl sulfide and dimethyl disulfide were 0 parts by weight. The resulting epoxy resin mixture had an epoxy equivalent of 289 g / eq., a softening point of 67.1°C, and an ICI melt viscosity of 0.24 Pa s (150°C). The sulfur content in epoxy resin (EP4) was determined by combustion quantification to be less than 5 ppm. Analysis by gel permeation chromatography confirmed that n=1 was 21.5 area % (UV-254 nm). Furthermore, ion chromatography of the extracted water (extracted at 95°C) confirmed that the quantitative value of sulfide ions was less than 1 ppm.

[0076] Comparative Example 2: 200 parts by weight of the phenolic resin (P2) obtained in Synthesis Example 2, 381 parts by weight of epichlorohydrin, 45 parts by weight of dimethyl sulfoxide, and 5 parts by weight of butanol were charged into a reaction vessel, stirred under a nitrogen atmosphere, and dissolved. After that, 39 parts by weight of flaky sodium hydroxide was continuously added over 2 hours while maintaining the temperature at 45°C. After completion of the sodium hydroxide addition, the reaction was further carried out at 45°C for 2 hours and then at 70°C for 1 hour. Subsequently, the mixture was repeatedly washed with water to remove by-product salts, and excess epichlorohydrin and the like were distilled from the oil layer under heating and reduced pressure. 444 parts by weight of methyl isobutyl ketone was added to the residue and dissolved. This methyl isobutyl ketone solution was heated to 70°C, and 10 parts by weight of a 30% aqueous sodium hydroxide solution was added. The reaction was allowed to proceed for 1 hour, after which the reaction solution was repeatedly washed with water until the washings became neutral. Next, methyl isobutyl ketone was distilled off from the oil layer under heating and reduced pressure, yielding 211 parts by weight of epoxy resin (EP5). The resulting epoxy resin had an epoxy equivalent of 312 g / eq., a softening point of 66.9°C, and an ICI melt viscosity of 0.25 Pa s (150°C). The sulfur content in epoxy resin (EP5) was determined by combustion quantification to be less than 5 ppm. Analysis by gel permeation chromatography confirmed that n=1 was 21.4 area % (UV-254 nm). Furthermore, ion chromatography of the extracted water (extracted at 95°C) confirmed that the quantitative value of sulfide ions was <1 ppm.

[0077] [Examples 4, 5, 6, Comparative Example 3] Epoxy resins (EP1, EP2, EP3) and a comparative epoxy resin (EP5) were used as the base resin, respectively, and phenol novolak (abbreviation: PN, hydroxyl group equivalent: 106 g / eq.) was used as the curing agent, and triphenylphosphine (abbreviation: TPP) was used as the curing accelerator, and these were blended in the weight ratios shown in the formulation in Table 1. The mixtures were kneaded using a twin roll mill and formed into tablets, and then a resin molded product was prepared by transfer molding. The resin was cured at 160°C for 2 hours and then at 180°C for 6 hours.

[0078] The physical properties were measured under the following conditions: Three-point bending test Manufacturer: A&D Co., Ltd. Equipment: RTG-1310 Test speed: 3 mm / min Distance between supports: 64 mm Measurement temperature: 30°C Figure 1 shows the stress-strain diagram when the three-point bending test was performed.

[0079]

[0080] [Examples 7, 8, 9, Comparative Example 4] Epoxy resins (EP1, EP2, EP3) and a comparative epoxy resin (EP5) were used as the base resin, respectively, and phenol novolak (abbreviation: PN, hydroxyl group equivalent: 103 g / eq.) was used as the curing agent, and triphenylphosphine (abbreviation: TPP) was used as the curing accelerator. These were blended in the weight ratios shown in the formulation in Table 2, kneaded using a twin roll and formed into tablets. Resin molded bodies were then prepared by transfer molding, and cured at 160°C for 2 hours, and then at 180°C for 6 hours.

[0081] The physical properties were measured under the following conditions: Three-point bending test Manufacturer: A&D Co., Ltd. Equipment: RTG-1310 Test speed: 3 mm / min Distance between supports: 64 mm Measurement temperature: 120°C Figure 2 shows the stress-strain diagram when the three-point bending test was performed.

[0082]

[0083] From the results in Table 1 and Figure 1, it was confirmed that Examples 4 to 6 had excellent maximum point stress and strain at 30°C. Furthermore, from the results in Table 2 and Figure 2, it was confirmed that Examples 7 and 8 had excellent maximum point stress and strain at 120°C. In particular, it was confirmed that Examples 5 and 7, which had a large sulfur content, had particularly excellent maximum point stress and strain at both 30°C and 120°C.

[0084] That is, it was confirmed that the epoxy resin mixture of the present invention can give a cured product that exhibits excellent mechanical strength and toughness at room temperature and in the high temperature range.

[0085] The present invention is useful for applications such as insulating materials for electric and electronic components (such as highly reliable semiconductor encapsulation materials), laminates (such as printed wiring boards and build-up boards), various composite materials including FRP, adhesives, paints, and the like, and is particularly useful for applications such as laminates, metal foil-clad laminates, insulating materials for build-up boards, and flexible board materials.

Claims

1. An epoxy resin mixture containing an epoxy resin represented by the following formula (1) and having a sulfur content of 15 ppm to 400 ppm by a combustion method. (In formula (1), n is the number of repetitions and represents a real number from 1 to 20.) 2. An epoxy resin mixture obtained by reacting a phenol resin represented by the following formula (2), epichlorohydrin, and a sulfur-containing compound. (In formula (2), n is the number of repetitions and represents a real number from 1 to 20.) 3. An epoxy resin composition containing the epoxy resin mixture according to claim 1 or 2 and a curing agent.

4. A cured product obtained by curing the epoxy resin composition according to claim 3.