JP7754606B2 - Epoxy resin composition - Google Patents

Description

The present invention relates to an epoxy resin composition. In particular, it relates to an epoxy resin composition used to seal or bond small electronic or electrical components such as relays and coils.

Small electronic or electrical components such as relays and coils are widely used in communication equipment, office automation equipment, home appliances, vending machines, and more, and these components are now mostly mounted on printed wiring boards. When components such as relays, which contain multiple parts housed in a single case, are mounted on a printed wiring board, they require a complete hermetic seal using resin or other materials to prevent the intrusion of solder flux, enable the components to be washed with solvents, and maintain airtightness after solder reflow processing.

Epoxy resins, for example, are commonly used as sealing materials for achieving such completely airtight seals. Among these, so-called one-component epoxy resin compositions, in which a latent curing agent such as dicyandiamide is mixed with the epoxy resin composition beforehand, are commonly used. On the other hand, small electronic or electrical components such as relays typically have cases and bodies made primarily of resin materials (such as polybutylene terephthalate (PBT) or liquid crystal polymer (LCP)), so the curing temperature of the sealing material should be 120°C or below.

In addition, noise issues caused by electrical appliances using these components in living spaces have recently become a prominent issue, and there is a particular need to reduce noise generated by components with moving parts, such as relays. One method of reducing such noise has been proposed, which involves imparting vibration-damping properties to the sealing material mentioned above (see, for example, Patent Documents 1 and 2).

JP 2008-115198 A JP 2011-079957 A

However, the epoxy resin compositions described in Patent Documents 1 and 2 did not provide fully satisfactory moist heat resistance to the resulting cured products.

The object of the present invention is to provide an epoxy resin composition that can be cured at temperatures of 120°C or less and that gives a cured product with excellent vibration damping properties and improved moist heat resistance.

As a result of extensive research into resolving the above-mentioned problems, the inventors have discovered that the above-mentioned problems can be solved by using an epoxy resin composition containing (A) a blocked polyurethane, (B) an epoxy resin having more than two glycidyl groups per molecule, (C) an epoxy resin having two or fewer glycidyl groups per molecule, and (D) a latent curing agent in certain proportions. Specifically, the present invention includes the following:

[1]
An epoxy resin composition comprising the following components (A), (B), (C), and (D), wherein the content of (A) is 20 to 60 parts by weight per 100 parts by weight of the total of (A), (B), and (C), and the content of (B) is 5 to 30 parts by weight per 100 parts by weight of the total of (B) and (C).
(A) Blocked polyurethane (B) Epoxy resin having more than two glycidyl groups per molecule (C) Epoxy resin having two or less glycidyl groups per molecule (D) Latent curing agent

[2]
The epoxy resin composition according to [1], wherein (B) the epoxy resin having more than two glycidyl groups in one molecule is at least one epoxy resin selected from the group consisting of aromatic amine-type epoxy resins, aminophenol-type epoxy resins, and aliphatic epoxy resins.

[3]
The epoxy resin composition according to [1] or [2], which is an epoxy resin composition for sealing or fixing small electronic or electrical components.

The present invention provides an epoxy resin composition that can be cured at temperatures of 120°C or less and that gives a cured product with excellent vibration damping properties and improved moist heat resistance. In particular, the epoxy resin composition of the present invention surprisingly contains a certain proportion of an epoxy resin containing more than two glycidyl groups per molecule, which was previously thought to be unsuitable for improving vibration damping properties due to the high crosslink density of the cured product upon curing. However, this composition gives a cured product that, upon curing, has excellent vibration damping properties and moist heat resistance, as well as excellent heat resistance and adhesion to resins and metals. Therefore, the epoxy resin composition of the present invention can be suitably used as an encapsulant for small electronic or electrical components with driving units, such as relays.

<Epoxy Resin Composition>
The epoxy resin composition of the present invention contains (A) a blocked polyurethane, (B) an epoxy resin having more than two glycidyl groups in one molecule, (C) an epoxy resin having not more than two glycidyl groups in one molecule, and (D) a latent curing agent.

[(A) Blocked Polyurethane]
In the present invention, (A) blocked polyurethane refers to a compound obtained by blocking, with an active hydrogen compound (blocking agent), the active isocyanate groups at the terminals of a urethane prepolymer obtained by reacting a polyhydroxy compound such as polyether polyol or polyester polyol with a polyisocyanate.

The polyether polyols can be obtained, for example, by reacting a polyol or amine with an alkylene oxide. Examples of polyols include dihydric alcohols such as ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, 1,3-butanediol, 1,4-butanediol, and 1,6-hexanediol; bisphenols such as 4,4'-dihydroxyphenylpropane and 4,4'-dihydroxyphenylmethane; and polyhydric alcohols such as glycerin, diglycerin, 1,1,1-trimethylolpropane, 1,2,5-hexanetriol, pentaerythritol, triethanolamine, sorbitol, and sugar. Examples of amines include diamines such as ethylenediamine and aromatic diamines. Examples of alkylene oxides include ethylene oxide, propylene oxide, butylene oxide, and α-olefin oxide.

The polyester polyol can be obtained, for example, by reacting a polycarboxylic acid with a polyol. Examples of polycarboxylic acids include dicarboxylic acids such as maleic acid, fumaric acid, adipic acid, and phthalic acid, and their acid anhydrides, as well as hydroxy-containing long-chain fatty acids such as ricinoleic acid, hydroxycaproic acid, hydroxycapric acid, hydroxyundecanoic acid, hydroxylinoleic acid, hydroxystearic acid, and hydroxyhexanedecenoic acid. In addition to the above, examples of polyols include addition polymers of alkylene oxides with aliphatic, alicyclic, or aromatic amines, or polyamide polyamines. Specific examples of such addition polymers include addition polymers of phthalic acid dihydrazide, ethylenediamine, adipic acid dihydrazide, hydrogenated methylenediphenyldiamine, or aniline with polypropylene oxide.

Examples of the polyisocyanate include aromatic isocyanates such as 4,4'-diphenylmethane diisocyanate (4,4'-MDI), 2,4'-diphenylmethane diisocyanate (2,4'-MDI), and toluene diisocyanate (TDI), and aliphatic isocyanates such as trimethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate (HDI), 1,2-propane diisocyanate, 1,2-butane diisocyanate, trimethylhexamethylene diisocyanate, isophorone diisocyanate (IPDI), 4,4'-dicyclohexylmethane diisocyanate, and cyclohexylene diisocyanate.

In addition, examples of active hydrogen compounds used as the blocking agent include oximes such as formamide oxime, acetamide oxime, acetoxime, methyl ethyl ketoxime, diacetyl monooxime, benzophenone oxime, and cyclohexanone oxime; phenols such as phenol, cresol, xylenol, ethylphenol, and t-butylphenol; alcohols such as methanol, ethanol, propanol, isopropanol, butanol, and 2-ethylhexanol; pyrazoles such as pyrazole, 3-methylpyrazole, and 3,5-dimethylpyrazole; β-diketones such as acetylacetone; β-ketoesters such as diethyl malonate, dimethyl malonate, ethyl acetoacetate, and methyl acetoacetate; dialkylamines such as dicyclohexylamine; and lactams such as ε-caprolactam, δ-valerolactam, β-butyrolactam, and β-propiolactam.

These blocked polyurethanes may be commercially available products. Examples of commercially available products include Takenate B-7005, B-7030, and B-7005 (all TDI-based blocked isocyanates, 100% active ingredient, manufactured by Mitsui Chemicals), Takenate B-5010 (TDI-based blocked isocyanate, 100% active ingredient, manufactured by Mitsui Chemicals), and Adeka Resin QR-9466 (IPDI-based blocked isocyanate, 100% active ingredient, manufactured by ADEKA).

The above-mentioned blocked polyurethanes may be used alone or in combination of two or more types.

[(B) Epoxy resin having more than two glycidyl groups in one molecule]
Examples of epoxy resins having more than two glycidyl groups in one molecule that can be used in the present invention include 2-[4-(2,3-epoxypropoxy)phenyl]-2-[4-[1,1-bis[4-([2,3-epoxypropoxy]phenyl)]ethyl]phenyl]propane, 1,3-bis[4-[1-[4-(2,3-epoxypropoxy)phenyl]-1-[4-[1-[4-(2,3-epoxypropoxyphenyl)-1-methylethyl]phenyl]ethyl]phenoxy]-2-propanol, naphthalene-type tetrafunctional epoxy resins, epoxy resins having a dicyclopentadiene skeleton, epoxy resins having a triazine skeleton, phenol novolac-type epoxy resins, and cresol novolac-type epoxy resins. Examples of epoxy resins include novolac epoxy resins such as bisphenol A novolac epoxy resins, biphenylaralkyl epoxy resins, tetrakisphenolethane epoxy resins, trishydroxyphenylmethane epoxy resins, aromatic amine epoxy resins, aliphatic amine epoxy resins, alicyclic amine epoxy resins, diphenyldiaminomethane epoxy resins, and aminophenol epoxy resins, as well as glycidylamine epoxy compounds such as trimethylolpropane polyglycidyl ether and pentaerythritol polyglycidyl ether, and epoxy group-containing polymers such as epoxy-modified butadiene and epoxy-modified acrylic-styrene polymers. These epoxy resins having more than two glycidyl groups per molecule may be used alone or in combination of two or more. Furthermore, they are preferably liquid at room temperature (25°C), and more preferably have low viscosity, because this improves flow into narrow gaps when hermetically sealing or insulating electrical and electronic components such as relays. Among these epoxy resins, aromatic amine-type epoxy resins, aminophenol-type epoxy resins, and aliphatic epoxy resins are preferred, and aromatic amine-type epoxy resins (N,N,N',N'-tetraglycidyl-4,4'-diaminodiphenyl ether, tetraglycidyl metaxylenediamine, etc.) and aminophenol-type epoxy resins (N,N,O-triglycidyl-p-aminophenol, N,N,O-triglycidyl-p-amino-m-cresol, etc.) are more preferred.

These epoxy resins containing more than two glycidyl groups per molecule may be commercially available. Examples of commercially available aromatic amine-type epoxy resins include jER604 (N,N,N',N'-tetraglycidyl-4,4'-diaminodiphenyl ether, manufactured by Mitsubishi Chemical Corporation), Sumiepoxy ELM-434, ELM-434VL, and ELM-434L (all N,N,N',N'-tetraglycidyl-4,4'-diaminodiphenyl ether, manufactured by Sumitomo Chemical Co., Ltd.), and TETRAD-X (tetraglycidyl metaxylenediamine, manufactured by Mitsubishi Gas Chemical Company, Inc.). Examples of alicyclic amine-type epoxy resins include TETRAD-C (1,3'-bis(N,N-diglycidylaminomethyl)cyclohexane, manufactured by Mitsubishi Gas Chemical Company, Inc.). Examples of aminophenol-type epoxy resins include jER630 (N,N,O-triglycidyl-p-aminophenol, manufactured by Mitsubishi Chemical Corporation), Sumiepoxy ELM-100H, ELM-100 (N,N,O-triglycidyl-p-amino-m-cresol, manufactured by Sumitomo Chemical Co., Ltd.), etc. Examples of aliphatic epoxy resins include Denacol EX-411 (pentaerythritol polyglycidyl ether, manufactured by Nagase ChemteX Corporation), SR-TMP, SR-TMPL (hereinafter referred to as trimethylolpropane polyglycidyl ether, manufactured by Sakamoto Pharmaceutical Co., Ltd.), etc.

Among the commercially available epoxy resins listed above that have more than two glycidyl groups per molecule, those with low viscosity are preferred because they improve flow into narrow gaps when hermetically sealing or insulating electrical and electronic components such as relays. Specifically, jER630, ELM-100, TETRAD-X, and SR-TMP are preferred, with jER630, ELM-100, and TETRAD-X being more preferred. Furthermore, these epoxy resins with more than two glycidyl groups per molecule may be used alone, or two or more types may be used in combination.

<(C) Epoxy Resin Having Two or Less Glycidyl Groups in One Molecule>
Examples of epoxy resins having two or less glycidyl groups per molecule that can be used in the present invention include bisphenol A type epoxy resins, bisphenol F type epoxy resins, bisphenol AD type epoxy resins, alkylene oxide-modified bisphenol epoxy resins, naphthalene type bifunctional epoxy resins, biphenyl type epoxy resins, alicyclic epoxy resins (cyclohexene oxide or cyclopentene oxide-containing compounds obtained by epoxidizing cyclohexene or cyclopentene ring-containing compounds with an oxidizing agent, or polyglycidyl ethers of dihydric or lower alcohols having at least one alicyclic ring, hydrogenated bisphenol type epoxy resins, etc.), dihydric epoxy resins such as catechol and resorcinol. Examples of such epoxy resins include polyglycidyl ethers obtained by reacting a dihydric alcohol such as phenol, 1,4-butanediol, 1,6-hexanediol, 2,2-dimethyl-1,3-propanediol (neopentyl glycol), (poly)ethylene glycol, or (poly)propylene glycol with epihalohydrin, glycidyl ether esters obtained by reacting a hydroxycarboxylic acid such as p-oxybenzoic acid with epihalohydrin, polyglycidyl esters obtained by reacting a dicarboxylic acid such as phthalic acid, terephthalic acid, hexahydrophthalic acid, or a long-chain dibasic acid with epihalohydrin, rubber-modified epoxy resins, urethane-modified epoxy resins, epoxy plasticizers, and monofunctional epoxy compounds. These epoxy resins having two or less glycidyl groups per molecule may be used alone, or two or more types may be used in combination.

Epoxy resins having two or fewer glycidyl groups per molecule typically contain at least 50 parts by weight, and preferably at least 70 parts by weight, of epoxy resins having two glycidyl groups per molecule per 100 parts by weight of the total epoxy resin. Furthermore, they are preferably liquid at room temperature (25°C), and even more preferably have low viscosity, as this improves flow into narrow gaps when hermetically sealing or insulating relays and other electrical and electronic components.

Among the above-mentioned epoxy resins having two or less glycidyl groups per molecule, bisphenol A epoxy resins, bisphenol F epoxy resins, alkylene oxide-modified bisphenol epoxy resins, polyglycidyl ethers obtained by reacting a dihydric phenol or dihydric alcohol with epihalohydrin, polyglycidyl esters obtained by reacting a dicarboxylic acid with epihalohydrin, and epoxy plasticizers are preferred, and bisphenol A epoxy resins, bisphenol F epoxy resins, alkylene oxide-modified bisphenol epoxy resins, polyglycidyl ethers obtained by reacting a dihydric phenol or dihydric alcohol with epihalohydrin, and polyglycidyl esters obtained by reacting a dicarboxylic acid with epihalohydrin are more preferred.

These epoxy resins having two or less glycidyl groups per molecule may be commercially available products. Examples of commercially available bisphenol A epoxy resins include D.E.R. 331 and D.E.R. 383 (manufactured by OLIN Corporation), jER828 and jER828EL (manufactured by Mitsubishi Chemical Corporation), Epiclon 850 and Epiclon 850-S (manufactured by DIC Corporation), etc. Examples of bisphenol F epoxy resins include jER807 (manufactured by Mitsubishi Chemical Corporation), Epiclon 830 and Epiclon 830-S (manufactured by DIC Corporation), etc. Examples of alkylene oxide-modified bisphenol epoxy resins include Rikaresin BEO-20E (bisphenol A bis(propylene glycol glycidyl ether) ether, manufactured by New Japan Chemical Co., Ltd.), Rikaresin BEO-60E (bisphenol A bis(triethylene glycol glycidyl ether) ether (main component), manufactured by New Japan Chemical Co., Ltd.), and ADEKA Resin EP-4000 and EP-4005 (all propylene oxide-modified bisphenol epoxy resins, manufactured by ADEKA Corporation). Examples of polyglycidyl ethers obtained by reacting a dihydric phenol or a dihydric alcohol with an epihalohydrin include Denacol EX-201 (resorcinol diglycidyl ether, manufactured by Nagase ChemteX Corporation), Denacol EX-211 (neopentyl glycol diglycidyl ether, manufactured by Nagase ChemteX Corporation), Denacol EX-212 (1,6-hexanediol diglycidyl ether, manufactured by Nagase ChemteX Corporation), Denacol EX-810, 811, 821, 830, 832, 841, 850, 851, 861 ((poly)ethylene glycol diglycidyl ether, manufactured by Nagase ChemteX Corporation), and Denacol EX-931 (polypropylene glycol diglycidyl ether, manufactured by Nagase ChemteX Corporation). Examples of polyglycidyl esters obtained by reacting a divalent carboxylic acid with an epihalohydrin include Denacol EX-721 (phthalic acid diglycidyl ester, manufactured by Nagase ChemteX Corporation), Denacol EX-711 (terephthalic acid diglycidyl ester, manufactured by Nagase ChemteX Corporation), SR-HHPA (hexahydrophthalic acid diglycidyl ester, manufactured by Sakamoto Pharmaceutical Industry Co., Ltd.), IPU-22G (8,13-dimethyl-8,12-eicosadienedioic acid bis(oxiranylmethyl)ester, manufactured by Okamura Oil Mills, Ltd.), and SB-20G (7-ethyloctadecanedioic acid di(2,3-3-epoxypropyl), manufactured by Okamura Oil Mills, Ltd.). Examples of alicyclic epoxy resins include Celloxide 2021P (3',4'-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate, manufactured by Daicel Corporation), Celloxide 2081 (ε-caprolactone-modified 3',4'-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate, manufactured by Daicel Corporation), Celloxide 3000 (1,2,8,9-diepoxylimonene, manufactured by Daicel Corporation), Epocalic THI-DE (tetrahydroindene diepoxide ^, manufactured by JXTG Nippon Oil & Energy Corporation), and Epocalic DE-102 (5,12-dioxahexacyclo[7.6.1.0] ^{4,6.0 10,15.0 11,13} ]hexadecane, manufactured by JXTG Nippon Oil & Energy Corporation), Epocalic DE-103 (5,12-dioxaheptacyclo[7.6.1.1 ^3,7 .0 ^2,8 .0 ^4,6 .0 ^10,15 .0 ^11,13 ]heptadecane, manufactured by JXTG Nippon Oil & Energy Corporation), SR-SBA (hydrogenated bisphenol A diglycidyl ether, manufactured by Sakamoto Pharmaceutical Industry Co., Ltd.), and Rikaresin DME-100 (cyclohexanedimethanol diglycidyl ether, manufactured by New Japan Chemical Co., Ltd.). Examples of epoxy plasticizers include Sanso Cizer E-PS (di-2-ethylhexyl 4,5-epoxycyclohexane-1,2-dicarboxylate, manufactured by New Japan Chemical Co., Ltd.), Sanso Cizer E-PO (di(9,10-epoxystearyl) 4,5-epoxycyclohexane-1,2-dicarboxylate, manufactured by New Japan Chemical Co., Ltd.), Sanso Cizer E-2000H (epoxidized soybean oil, manufactured by New Japan Chemical Co., Ltd.), Sanso Cizer E-9000H (epoxidized linseed oil, manufactured by New Japan Chemical Co., Ltd.), Adeka Cizer O-130P (epoxidized soybean oil, manufactured by ADEKA Corporation), and Adeka Cizer O-180A (epoxidized linseed oil, manufactured by ADEKA Corporation).

Among the above-mentioned commercially available epoxy resins having two or less glycidyl groups per molecule, D.E.R. 331, D.E.R. 383, jER828, jER828EL, Epicron 850, Epicron 850-S, jER807, Epicron 830, Epicron 830-S, Rikaresin BEO-60E, Adekaresin EP-4000, Adekaresin EP-4005, SR-HHPA, Rikaresin DME-100, Sanso Cizer E-PO, Sanso Cizer E-PS, and Adeka Cizer O-180A are preferred, and D.E.R. 331, D.E.R. D.E.R. 383, jER828, jER828EL, Epicron 850, Epicron 850-S, jER807, Epicron 830, Epicron 830-S, Rikaresin BEO-60E, ADEKA RESIN EP-4000, ADEKA RESIN EP-4005, SR-HHPA, and Rikaresin DME-100 are more preferred, with D.E.R. 331, jER807, ADEKA RESIN EP-4005, SR-HHPA, and Rikaresin DME-100 being particularly preferred. Furthermore, epoxy resins having two or less glycidyl groups per molecule may be used alone or in combination of two or more types.

<Proportions of (A), (B), and (C) Contained in Epoxy Resin Composition>
The content of (A) in the epoxy resin composition of the present invention is 20 to 60 parts by weight, preferably 30 to 45 parts by weight, per 100 parts by weight of the total amount of (A), (B), and (C). If it is 20 parts by weight or less, the loss tangent (tan δ) of the resulting cured product at room temperature will decrease, resulting in reduced vibration damping properties. If it is 60 parts by weight or more, the curing rate will decrease.

The content of (B) in the epoxy resin composition of the present invention is 5 to 30 parts by weight, preferably 10 to 25 parts by weight, per 100 parts by weight of the total amount of (B) and (C). If it is 5 parts by weight or less, the adhesiveness to resins and metals, moist heat resistance, and heat resistance of the resulting cured product will decrease. If it is 30 parts by weight or more, the loss tangent (tan δ) of the resulting cured product at room temperature will decrease, resulting in reduced vibration damping properties.

<(D) Latent Curing Agent>
The latent curing agent used in the present invention is not particularly limited as long as it does not impair the performance after curing. Specific examples include dihydrazide compounds, dicyandiamide, imidazole compounds, imidazole adduct compounds, amine adduct compounds, modified aliphatic polyamine compounds, etc. Examples of dihydrazide compounds include adipic acid dihydrazide, sebacic acid dihydrazide, isophthalic acid dihydrazide, maleic acid dihydrazide, dodecanedioic acid dihydrazide, Amicure VDH and Amicure UDH manufactured by Ajinomoto Technofine Co., Ltd. Examples of imidazole compounds include 2-phenylimidazole and 2-phenyl-4-methyl-5-hydroxymethylimidazole. Examples of imidazole adduct compounds include Amicure PN-23 and Amicure PN-R manufactured by Ajinomoto Technofine Co., Ltd. Examples of the amine adduct compounds include Amicure MY-24 and Amicure MY-R manufactured by Ajinomoto Technofine Co., Ltd., and the adduct compounds disclosed in JP-A-57-100127 and JP-A-2017-178981. Examples of the modified aliphatic polyamine compounds include Fujicure FXE-1000 manufactured by T&K Toka.

Of these latent curing agents, dihydrazide compounds and amine adduct compounds are preferred. Furthermore, latent curing agents may be used alone or in combination of two or more types.

The amount of latent curing agent contained in the epoxy resin composition of the present invention is, for example, 3 to 30 parts by weight, preferably 10 to 20 parts by weight, per 100 parts by weight of the total amount of (A), (B), and (C).

<Other ingredients>
The epoxy resin composition of the present invention may optionally contain a blocked polyurethane dissociation accelerator, organic filler, inorganic filler, coupling agent, colorant, non-reactive diluent, antifoaming agent, wetting and dispersing agent, etc. Examples of blocked polyurethane dissociation accelerators include metal catalysts such as organotin compounds, amine catalysts such as 1,8-diazabicyclo[5,4,0]-undecene-7, and salts thereof. Examples of inorganic fillers include calcium carbonate, barium sulfate, fused silica, crystalline silica, glass filler, aluminum hydroxide, magnesium hydroxide, alumina, etc. Examples of coupling agents include 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, etc. Examples of colorants include carbon black, titanium oxide, etc. Examples of non-reactive diluents include organic solvents such as xylene and cellosolve, and plasticizers such as dimethyl phthalate, dibutyl phthalate, diisononyl phthalate, and tricresyl phosphate.

<Method for preparing epoxy resin composition>
The method for preparing the epoxy resin composition of the present invention employs common stirring and mixing equipment and mixing conditions similar to those used in the preparation of conventional epoxy resin compositions. Equipment that can be used includes a mixing roll, dissolver, planetary mixer, kneader, extruder, etc. During mixing, the epoxy resin, etc. may be heated to dissolve and/or reduce viscosity and improve stirring and mixing efficiency. Cooling may also be performed as needed to remove frictional heat, reaction heat, etc. The stirring and mixing time may be determined as needed and is not subject to any particular restrictions.

<Curing conditions>
The curing conditions are not particularly limited, but the curing temperature is, for example, 80°C to 150°C, preferably 90°C to 130°C. In the case of bonding, sealing, etc. of resin materials (such as polybutylene terephthalate (PBT) and liquid crystal polymer (LCP)), a temperature of 120°C or less is preferred. When the curing temperature is 120°C, the curing time is, for example, 15 minutes to 2 hours, preferably 30 minutes to 90 minutes. Note that the epoxy resin composition of the present invention can be cured even at a relatively low temperature of around 120°C, and therefore can also be suitably used as a low-temperature curing sealant.

<Characteristics of the epoxy resin of the present invention>
The epoxy resin of the present invention, when cured as described above, typically exhibits a loss tangent (tan δ) at room temperature of 0.10 or more, preferably 0.25 or more. Because of this, the cured product has excellent vibration-damping properties and is therefore suitable for use as an epoxy resin composition for sealing or adhering small electronic or electrical components, particularly for sealing or adhering relays or coils. The loss tangent (tan δ) at room temperature in the present invention is a value measured under the conditions described in the Examples section below.

Furthermore, the epoxy resin composition of the present invention can be made into a one-component epoxy resin composition that is liquid at 25°C by using (B) an epoxy resin having more than two glycidyl groups per molecule and/or (C) an epoxy resin having two or less glycidyl groups per molecule that is liquid at 25°C, as necessary.

The present invention will be explained in detail below using examples and comparative examples, but the present invention is not limited to these examples in any way.

(Examples 1 to 10, Comparative Examples 1 to 3)
Each component was weighed according to Table 1 and stirred and mixed using a mixing roll to prepare epoxy resin compositions according to each Example and Comparative Example. Various tests were performed using the obtained epoxy resin compositions using the following methods. The results are shown in Table 2. Note that the units of each value in Table 1 are parts by weight unless otherwise specified. The amount of Fuji EP Black 8017 in Table 1 indicates the amount of carbon black contained in Fuji EP Black 8017 (20% by weight), and the amount of jER807 indicates the combined amount of bisphenol F epoxy resin (80% by weight) contained in Fuji EP Black 8017.

(Measurement of gel time)
Measurements were carried out using the following equipment and conditions, and the evaluations were carried out as follows.
Measurement equipment: Hot plate gelation tester GT-D (manufactured by Nissin Scientific Co., Ltd.)
Measurement method: 0.1 g of sample was taken with a spatula, heated on a hot plate set to 100°C, mixed with the spatula at appropriate times, and the time until it became a solid mass was measured. The results are shown in Table 2.

(Measurement of dynamic viscoelasticity and evaluation of vibration damping properties)
The epoxy resin compositions obtained in each of the Examples and Comparative Examples were cured at 120°C for 60 minutes to obtain cured products. Test pieces measuring 3 mm x 5 mm x 50 mm were prepared from the obtained cured products, and the dynamic viscoelasticity of the prepared test pieces was measured at 30°C and 10 Hz in tension mode (heating rate 2°C/min) using a dynamic viscoelasticity tester (SII DMS-6100 (manufactured by Hitachi High-Tech Science Corporation)). The vibration damping properties were evaluated based on the obtained loss tangent (tanδ) values according to the criteria shown below. The evaluation results are shown in Table 2.
・Loss tangent (tanδ)
◎: 0.25 or more, ○: 0.10 to 0.24, ×: 0.09 or less

(Measurement of Tensile Shear Adhesion Strength)
The epoxy resin compositions obtained in each of the Examples and Comparative Examples were applied between two steel plates (1.6 mm x 25 mm x 100 mm) and two PBT plates (Duranex (registered trademark) PBT3300 ((GF 30% reinforced), manufactured by Polyblastex Corporation, 1.6 mm x 25 mm x 100 mm), which were then laminated together and cured at 120°C for 60 minutes to prepare test specimens. The PBT-PBT and steel-steel adhesive strengths of the prepared test specimens were measured in accordance with the tensile shear strength (TSS) measurement method of JIS K6850. The adhesive strength was evaluated according to the following criteria, and the results are shown in Table 2.
PBT - TSS of PBT (N/mm ² )
◎: 4.0 or more 〇: 3.0 to 3.9 ×: 2.9 or less Steel-to-steel TSS (N/mm ² )
◎: 11.0 or more ○: 9.0 to 10.9 ×: 8.9 or less

(Heat and humidity resistance under high temperature and humidity conditions and evaluation)
The epoxy resin composition obtained in each Example and Comparative Example was applied between two copper plates (1.6 mm x 25 mm x 100 mm), bonded together, and cured at 120°C for 60 minutes to prepare test specimens. The prepared test specimens and test specimens after further exposure to a temperature of 85°C and a humidity of 85% for 3 days were each measured for copper-to-copper adhesive strength in accordance with the tensile shear adhesive strength measurement method specified in JIS K6850. The retention rate was calculated from the measurement results, and the results were evaluated according to the following criteria. The evaluation results are shown in Table 2.
Retention rate (value calculated by {(copper-copper adhesive strength after exposure)/(copper-copper adhesive strength before exposure)}×100, %)
〇: 50% or more ×: 50% or less

(Determination of heat resistance of cured product)
The epoxy resin compositions obtained in each Example and Comparative Example were cured at 120°C for 60 minutes to obtain cured products. Test pieces measuring 3 mm x 25 mm x 50 mm were prepared from the cured products and exposed to 270°C for 3 minutes. After exposure, the test pieces were inspected for changes in appearance and flexibility, and the results were evaluated according to the following criteria. The evaluation results are shown in Table 2.
Appearance: 〇: No change △: Surface roughness ×: Foaming, deformation, stickiness

The components in Table 1 are as follows:
(A) Blocked polyurethane - ADEKA RESIN QR-9466: IPDI-based polyisocyanate (manufactured by ADEKA Corporation)
(B) Epoxy resin having more than two glycidyl groups in one molecule jER630: aminophenol-based trifunctional epoxy resin (manufactured by Mitsubishi Chemical Corporation)
SR-TMP: Aliphatic trifunctional epoxy resin (manufactured by Sakamoto Pharmaceutical Industries)
・TETRAD-X: Xylenediamine-based tetrafunctional epoxy resin (manufactured by Mitsubishi Gas Chemical Company, Inc.)
ELM-100: Aminocresol trifunctional epoxy resin (Sumitomo Chemical Co., Ltd.)
(C) Epoxy resin having two or less glycidyl groups per molecule jER807: bisphenol F type epoxy resin (manufactured by Mitsubishi Chemical Corporation)
D.E.R. 331: Bisphenol A type epoxy resin (manufactured by OLIN)
ADEKA RESIN EP-4005: propylene oxide modified bisphenol A type epoxy resin (manufactured by ADEKA Corporation)
Rikaresin DME-100: Cyclohexanedimethanol diglycidyl ether (manufactured by New Japan Chemical Co., Ltd.)
SR-HHPA: Hexahydrophthalic acid diglycidyl ether (manufactured by Sakamoto Pharmaceutical Industry Co., Ltd.)
Sanso Cizer E-PO: 4,5-epoxycyclohexane-1,2-dicarboxylic acid di(9,10-epoxystearyl) (manufactured by New Japan Chemical Co., Ltd.)
Adeka Cizer O-180A: Epoxidized linseed oil (manufactured by ADEKA Corporation)
(D) Latent Curing Agent Curing Agent A: Epoxy-amine adduct compound (manufactured by Taoka Chemical Co., Ltd.) disclosed in JP-A-57-100127
ADH: Adipic acid dihydrazide (manufactured by Nippon Phichem Co., Ltd.)
Amicure UDH: 7,11-octadecadiene-1,18-dicarbohydrazide (manufactured by Ajinomoto Technofine Co., Ltd.)
(filler)
Aerosil 200: hydrophilic fused silica (manufactured by Nippon Aerosil Co., Ltd.)
Miclone 200: Fatty acid-treated precipitated calcium carbonate (manufactured by NewLyme Co., Ltd.)
(Coloring agent)
Fuji EP Black 8017: 20 wt% carbon black-containing bisphenol F epoxy resin dispersion (manufactured by Fuji Pigment Co., Ltd.)

Claims (3)

An epoxy resin composition comprising the following components (A), (B), (C), and (D), wherein the content of (A) is 30 to 45 parts by weight per 100 parts by weight of the total of (A), (B), and (C), and the content of (B) is 5 to 30 parts by weight per 100 parts by weight of the total of (B) and (C).
(A) Blocked polyurethane (B) Epoxy resin having more than two glycidyl groups per molecule (C) Epoxy resin having two or less glycidyl groups per molecule (D) Latent curing agent The epoxy resin composition according to claim 1, wherein (B) the epoxy resin having more than two glycidyl groups per molecule is at least one epoxy resin selected from the group consisting of aromatic amine-type epoxy resins, aminophenol-type epoxy resins, and aliphatic epoxy resins. The epoxy resin composition according to claim 1 or 2, which is an epoxy resin composition for sealing or bonding small electronic or electrical components.