JP2024055687A - Epoxy resin adhesive composition and cured product thereof - Google Patents

Abstract

[Problem] The object of the present invention is to provide an epoxy resin adhesive composition that has excellent adhesive strength after a high temperature and high humidity environmental test of 85°C x 85% RH. [Solution] An epoxy resin adhesive composition comprising the following components (A) to (D). Component (A): epoxy resin; Component (B): curing agent that reacts with epoxy resin; Component (C): alkali metal hydroxide; Component (D): water. [Selected Figures] None

Description

The present invention relates to an epoxy resin adhesive composition and its cured product.

Conventionally, epoxy resin adhesive compositions have been widely used in the assembly of electrical components and the like due to their excellent adhesive strength, high strength, heat resistance, electrical properties, and chemical resistance. However, epoxy resin adhesive compositions are generally known to have poor moisture resistance due to the presence of ether bonds and the like in the molecule. As a method for improving moisture resistance, Cited Document 1 discloses an epoxy resin adhesive composition that contains an epoxy resin, a powder of a tetrafluoroethylene polymer, and a coupling agent.

Japanese Patent Application Laid-Open No. 01-275686

However, the epoxy resin adhesive composition of Patent Document 1 had poor adhesive strength after a high-temperature, high-humidity environmental test at 85°C and 85% RH, and was therefore insufficient in reliability.

The present invention has been made in consideration of the above situation, and aims to provide an epoxy resin adhesive composition that has excellent adhesive strength after a high-temperature, high-humidity environmental test at 85°C and 85% RH.

The gist of the present invention will now be described.
[1] An epoxy resin adhesive composition comprising the following components (A) to (D):
Component (A): epoxy resin; Component (B): curing agent that reacts with epoxy resin; Component (C): alkali metal hydroxide; Component (D): water. [2] The epoxy resin adhesive composition according to [1], wherein the component (C) is sodium hydroxide or potassium hydroxide.
[3] The epoxy resin adhesive composition according to [1] or [2], further comprising a silane coupling agent as a component (E).
[4] The epoxy resin adhesive composition according to [1] or [2], wherein the amount of the (C) component is 0.2 to 20 parts by mass per 100 parts by mass of the (B) component.
[5] The epoxy resin adhesive composition according to [1] or [2], wherein the component (A) contains a bisphenol-type epoxy resin.
[6] The epoxy resin adhesive composition according to [1] or [2], wherein the component (B) contains a polyamine compound having an amine value of 200 to 700 KOHmg/g.
[7] The epoxy resin adhesive composition according to [1] or [2], which is used for an adherend made of an amphoteric metal.
[8] A two-component epoxy resin adhesive composition comprising the following components A and B:
Component A: (A) a composition containing an epoxy resin; Component B: a composition containing the following components (B) to (D); Component (B): a curing agent that reacts with an epoxy resin; Component (C): an alkali metal hydroxide; Component (D): water. [9] A cured product obtained by curing either the epoxy resin adhesive composition described in [1] or the two-component epoxy resin adhesive composition described in [8].
[8] The epoxy resin adhesive composition according to [7], wherein the amphoteric metal is aluminum or zinc.
[9] A two-component epoxy resin adhesive composition comprising the following components A and B:
Component A: (A) a composition containing an epoxy resin; Component B: a composition containing the following components (B) to (D); Component (B): a curing agent that reacts with an epoxy resin; Component (C): an alkali metal hydroxide; Component (D): water; [10] The two-component epoxy resin adhesive composition according to [9], further comprising a silane coupling agent as component (E) in component A or component B.
[11] A cured product obtained by curing either the epoxy resin adhesive composition according to [1] or the two-component epoxy resin adhesive composition according to [9].

The present invention provides an epoxy resin adhesive composition that has excellent adhesion after a high-temperature, high-humidity environmental test of 85°C x 85% RH. The present invention also provides an epoxy resin adhesive composition that has excellent adhesion to amphoteric metals and storage stability.

The details of the invention are described below. In this specification, "X to Y" is used to mean that the numerical values (X and Y) written before and after it are included as the lower and upper limits, respectively, and means "X or more and Y or less." In this specification, amphoteric metals refer to aluminum, zinc, tin, and lead, and oxides of amphoteric metals are not intended.
<Component (A)>
The component (A) used in the present invention is not particularly limited as long as it is an epoxy resin. The component (A) may be a multifunctional epoxy resin having two or more epoxy groups, a monofunctional epoxy compound having only one epoxy group, etc., and among them, a multifunctional epoxy resin is preferred. The component (A) may be liquid or solid, but is preferably liquid from the viewpoint of workability, and is preferably liquid from the viewpoint of adhesive strength.

The polyfunctional epoxy resin is not particularly limited, but may be bisphenol type epoxy resins such as bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type, and bisphenol AD type epoxy resin, hydrogenated bisphenol type epoxy resin, 1,2-butanediol diglycidyl ether, 1,3-butanediol diglycidyl ether, 1,4-butanediol diglycidyl ether, ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, 2,3-butanediol diglycidyl ether, 1,5-pentanediol diglycidyl ether, 1,6-hexanediol diglycidyl ether, 1,7-hexanediol diglycidyl ether, 1,8-hexanediol diglycidyl ether, 1,9-hexanediol diglycidyl ether, 2,10-hexanediol diglycidyl ether, 2,2-hexanediol diglycidyl ether, 2,3-hexanediol diglycidyl ether, 1,5-hexanediol diglycidyl ether, 2,3-hexanediol diglycidyl ether, 2,4-hexanediol diglycidyl ether, 2,5-hexanediol diglycidyl ether, 2,6-hexanediol diglycidyl ether, 2,7-hexanediol diglycidyl ether, 2,8-hexanediol diglycidyl ether, 2,9-hexanediol diglycidyl ether, 2,10 ... Examples of such epoxy resins include alkylene glycol epoxy resins such as Sandiol diglycidyl ether, neopentyl glycol diglycidyl ether, and 1,4-cyclohexanedimethanol diglycidyl ether, novolac epoxy resins such as phenol novolac epoxy resins and cresol novolac epoxy resins, glycidylamine compounds such as N,N-diglycidyl-4-glycidyloxyaniline, 4,4'-methylenebis(N,N-diglycidylaniline), tetraglycidyldiaminodiphenylmethane, and tetraglycidyl-m-xylylenediamine, and naphthalene epoxy resins having four glycidyl groups. Among these, bisphenol A epoxy resins are preferred from the viewpoint of excellent adhesion to amphoteric metals. These may be used alone or in combination.

Commercially available products of the multifunctional epoxy resins are not particularly limited, but include, for example, jER828, 1001, 801, 806, 807, 152, 604, 630, 871, YX8000, YX8034, and YX4000 (manufactured by Mitsubishi Chemical Corporation); Epicron 830, 850, 830LVP, 850CRP, 835LV, HP4032D, 703, 720, 726, and 820 (manufactured by DIC Corporation); EP4100, EP4000, EP4080, EP4085, EP4088, EPU6, EPU7N, EPR4023, and EPR1. 309, EP4920 (manufactured by ADEKA Corporation), TEPIC (manufactured by Nissan Chemical Industries, Ltd.); KF-101, KF-1001, KF-105, X-22-163B, X-22-9002 (manufactured by Shin-Etsu Chemical Co., Ltd.); Denacol EX411, 314, 201, 212, 252 (manufactured by Nagase ChemteX Corporation); DER-331, 332, 334, 431, 542 (manufactured by The Dow Chemical Company); YH-434, YH-434L (manufactured by Nippon Steel Chemical & Material Co., Ltd.), etc., but are not limited to these.

The monofunctional epoxy compound is not particularly limited, but examples thereof include n-butyl glycidyl ether, allyl glycidyl ether, 2-ethylhexyl glycidyl ether, styrene oxide, phenyl glycidyl ether, cresyl glycidyl ether, p-sec-butylphenyl glycidyl ether, glycidyl methacrylate, t-butylphenyl glycidyl ether, (poly)ethylene glycol glycidyl ether, butanediol glycidyl ether, etc. These may be used alone or in combination of two or more.

Commercially available products of the monofunctional epoxy compound are not particularly limited, but examples include ED-502, ED-502S, ED-509E, ED-509S, and ED-529 (manufactured by ADEKA Corporation). These may be used alone or in combination of two or more kinds.

<Component (B)>
The curing agent used in this invention that reacts with the epoxy resin (B) can be a known curing agent, such as a polyamine compound, a polymercaptan compound, a polyamide compound, etc., and among them, a polyamine compound is preferred because it has a better adhesive strength after a high-temperature and high-humidity environment test. In this specification, a polyamine compound may be referred to as an amine-based curing agent. Commercially available amine-based curing agents include ST12 manufactured by Mitsubishi Chemical Corporation.

The (B) component may be a solid such as a latent curing agent, but is preferably liquid at 25°C. The viscosity (25°C) of the (B) component is not particularly limited, but is 300 to 10,000 mPa·s, preferably 500 to 7,000 mPa·s, and particularly preferably 1,000 to 4,000 mPa·s. When the (B) component is a polyamine compound, the amine value is not particularly limited, but is 200 to 700 KOHmg/g, more preferably 250 to 550 KOHmg/g, and particularly preferably 300 to 450 KOHmg/g. By having the viscosity or amine value within the above range, the adhesive strength after the high temperature and high humidity environmental test is even more excellent. The amine value refers to the number of mg of potassium hydroxide equivalent to the perchloric acid required to neutralize all basic nitrogen contained in 1 g of sample. In the present invention, the amine value refers to a value measured in accordance with JIS K7237.

The polyamine compound may be an aliphatic polyamine, an alicyclic polyamine, an aromatic polyamine, or a polyamidoamine, and among these, an aliphatic polyamine, an alicyclic polyamine, or an aromatic polyamine is preferred. A mixture of two or more kinds may also be used.

Examples of the aliphatic polyamines include ethylenediamine, diethylenetriamine, triethylenetetramine, and hexamethylenediamine. Examples of the alicyclic polyamines include menthenediamine, isophoronediamine, N-aminoethylpiperazine, diaminodicyclohexylmethane, and norbornanediamine. Examples of the aromatic polyamines include xylylenediamine, metaxylylenediamine, metaphenylenediamine, diaminodiphenylmethane, diaminodiphenylsulfone, and diaminodiethyldiphenylmethane. These may be used alone or in combination of two or more.

The polymercaptan is not particularly limited, but may be 3,3'-dithiodipropionic acid, trimethylolpropane tris(thioglycolate), pentaerythritol tetrakis(thioglycolate), ethylene glycol dithioglycolate, 1,4-bis(3-mercaptobutyryloxy)butane, tris[(3-mercaptopropionyloxy)-ethyl]-isocyanurate (TEMPIC), 1,3,5-tris(3-mercaptobutyloxyethyl)-1,3,5-triazine-2,4,6(1H,3H ,5H)-trione, trimethylolpropane tris(3-mercaptopropionate) (TMMP), pentaerythritol tetrakis(3-mercaptopropionate) (PEMP), pentaerythritol tetrakis(3-mercaptobutyrate), dipentaerythritol hexakis(3-mercaptopropionate) (DPMP), alkyl polythiols such as 1,4-butanedithiol, 1,6-hexaneedithiol, and 1,10-decanedithiol; and polythioethers containing terminal thiol groups.

The polyamide compound may be a compound obtained by reacting a polyamine with a dicarboxylic acid.

The amount of component (B) added is not particularly limited, but is 1 to 200 parts by mass, preferably 2 to 100 parts by mass, and particularly preferably 3 to 75 parts by mass, per 100 parts by mass of component (A). It is preferable that the amount is within the above range, since it provides excellent adhesion to amphoteric metals.

<Component (C)>
The component (C) used in the present invention is not particularly limited as long as it is an alkali metal hydroxide. The component (C) can provide a remarkable effect of excellent adhesion to amphoteric metals, adhesion after high temperature and high humidity environmental testing, and storage stability by combining with other components of the present invention. The component (C) is not particularly limited, but examples thereof include sodium hydroxide, potassium hydroxide, lithium hydroxide, rubidium hydroxide, etc., and among them, sodium hydroxide and potassium hydroxide are preferred because of their excellent adhesion to amphoteric metals. These may be used alone or in combination of two or more.

The amount of the (C) component is 0.001 to 20 parts by mass, preferably 0.01 to 10 parts by mass, and particularly preferably 0.05 to 5 parts by mass, per 100 parts by mass of the (A) component. The amount of the (C) component is 0.001 to 40 parts by mass, preferably 0.005 to 20 parts by mass, and particularly preferably 0.01 to 10 parts by mass, per 100 parts by mass of the (B) component. By being within the above range, the adhesive strength to amphoteric metals, the adhesive strength after high temperature and high humidity environmental testing, and storage stability are even more excellent.

<Component (D)>
The component (D) of the present invention is not particularly limited as long as it is water, and examples thereof include distilled water and ion-exchanged water. The component (D) of the present invention, when combined with other components, can provide significant effects such as excellent adhesion to amphoteric metals, adhesion after high-temperature and high-humidity environmental testing, and storage stability. The component (D) can act as a solvent to dissolve the component (C).

The amount of the (D) component added is not particularly limited, but is 0.01 to 10 parts by mass, preferably 0.05 to 5 parts by mass, and particularly preferably 0.1 to 3 parts by mass, relative to 100 parts by mass of the (A) component. The amount of the (D) component added is 0.01 to 20 parts by mass, preferably 0.02 to 10 parts by mass, and particularly preferably 0.03 to 6 parts by mass, relative to 100 parts by mass of the (B) component. The amount of the (D) component added is 0.1 to 300 parts by mass, preferably 0.5 to 200 parts by mass, and particularly preferably 1 to 150 parts by mass, relative to 1 part by mass of the (C) component. By being within the above range, the adhesion to amphoteric metals, the adhesion after high temperature and high humidity environmental testing, and the storage stability are even more excellent.

<Component (E)>
Furthermore, the epoxy resin adhesive composition of the present invention may contain a silane coupling agent as component (E). Component (E) of the present invention has the effect of providing even better adhesive strength after high temperature and high humidity environmental testing when combined with other components of the present invention.

Examples of the silane coupling agents include glycidyl group-containing silane coupling agents such as 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, and 3-glycidoxypropylmethyldiethoxysilane; vinyl group-containing silane coupling agents such as vinyltris(β-methoxyethoxy)silane, vinyltriethoxysilane, and vinyltrimethoxysilane; (meth)acrylic group-containing silane coupling agents such as γ-methacryloxypropyltrimethoxysilane; amino group-containing silane coupling agents such as N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, and N-phenyl-γ-aminopropyltrimethoxysilane; and others such as γ-mercaptopropyltrimethoxysilane, γ-chloropropyltrimethoxysilane, styrylsilane, ureidosilane, sulfidosilane, and isocyanate silane. Among these, glycidyl group-containing silane coupling agents and amino group-containing silane coupling agents are preferred. These may be used alone or in combination of two or more.

The amount of the (E) component added is not particularly limited, but is preferably 0.1 to 20 parts by mass, more preferably 0.2 to 15 parts by mass, and even more preferably 0.3 to 10 parts by mass, relative to 100 parts by mass of the (A) component. Alternatively, the amount of the (E) component added is preferably 0.1 to 20 parts by mass, more preferably 0.2 to 15 parts by mass, and even more preferably 0.3 to 10 parts by mass, relative to 100 parts by mass of the (B) component. By being within the above range, the effect of even better adhesive strength after high temperature and high humidity environmental testing can be obtained.

<Optional ingredients>
Additives that can be used in the present invention include curing accelerators, fillers, various elastomers such as styrene copolymers, storage stabilizers, antioxidants, flame retardant agents, light stabilizers, heavy metal deactivators, plasticizers, defoamers, pigments, rust inhibitors, leveling agents, dispersants, rheology adjusters, flame retardants, and surfactants, provided that the object of the present invention is not impaired. Examples of the fillers include silica, glass, ceramics, calcium carbonate, carbon powder, and kaolin clay.

<Two-component epoxy resin adhesive composition>
The two-part epoxy resin adhesive composition according to one embodiment of the present invention contains an A-part and a B-part, the A-part being a composition containing the component (A), and the B-part being a composition containing the components (B) to (D). By dividing the components into separate liquids in this way, unnecessary reactions during storage can be suppressed, and storage stability can be improved. In such a two-part epoxy resin adhesive composition, each liquid can be produced by mixing by a known method. Then, the two liquids are mixed and used when used. The B-part is in the range of 5 to 300 parts by mass, more preferably 10 to 200 parts by mass, and particularly preferably 20 to 150 parts by mass, relative to 100 parts by mass of the A-part. The A-part and B-part can be mixed and stirred before use to obtain a cured product.

<Cured Product>
A cured product obtained by curing the epoxy resin adhesive composition of the present invention is also an aspect of the present invention. The curing conditions for the epoxy resin adhesive composition are not particularly limited, but a temperature of 0° C. or higher and lower than 150° C. is preferred, and more preferably 10° C. or higher and lower than 130° C. The curing time is not particularly limited, but may be, for example, 10 minutes to 30 days.

The cured product obtained by curing the two-component epoxy resin adhesive composition of the present invention is also an aspect of the invention. Curing by mixing two components means that the composition can be cured by mixing the two components when used. The curing conditions for the two-component epoxy resin adhesive composition are not particularly limited, but a temperature of 0°C or higher and lower than 150°C after mixing the two components is preferred, and more preferably 10°C or higher and lower than 130°C. The curing time is not particularly limited, but may be, for example, 10 minutes to 30 days.

<Applications>
As specific uses of the epoxy resin adhesive composition of the present invention, since the present invention is an epoxy resin adhesive composition having excellent adhesive strength after a high temperature and high humidity environment test of 85°C x 85% RH, in the automobile and transportation machinery field, it can be used as an adhesive for automobile switch parts, headlamps, engine internal parts, electrical components, drive engines, brake oil tanks, etc. Also, in flat panel displays, it can be used as an adhesive for liquid crystal displays, organic electroluminescence, light emitting diode display devices, and field emission displays. It can be used as an adhesive for electronic mobile devices such as mobile phones and multi-function mobile phones. In the recording field, it can be used as an adhesive for video discs, CDs, DVDs, MDs, pickup lenses, hard disk peripherals (spindle motor members, magnetic head actuator members, etc.), Blu-ray discs, etc. In the electronic materials field, it can be used as an adhesive for electronic components, electric circuits, electrical contacts, or sealing materials for semiconductor elements, die bonding agents, conductive adhesives, anisotropic conductive adhesives, interlayer adhesives for multilayer boards including build-up boards, solder resists, etc. In the battery field, it can be used as an adhesive for Li batteries, manganese batteries, alkaline batteries, nickel-based batteries, fuel cells, silicon-based solar cells, dye-sensitized solar cells, organic solar cells, etc. In the optical parts field, it can be used as an adhesive for optical switch peripherals in optical communication systems, optical fiber materials for optical connector peripherals, optical passive components, optical circuit components, and optical electronic integrated circuit peripherals. In the optical equipment field, it can be used as an adhesive for still camera lens materials, finder prisms, target prisms, finder covers, light receiving sensor parts, photographic lenses, projection lenses for projection televisions, etc. In the infrastructure field, it can be used as an adhesive for outdoor communication equipment, traffic lights, and other parts and modules that are left in outdoor environments for long periods of time.

The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these examples.

<Preparation of two-component epoxy resin adhesive composition>
Each component was taken in the parts by weight shown in Table 1 and mixed in a mixer at room temperature for 60 minutes to prepare components A and B, which correspond to two-part epoxy resin adhesive compositions. The detailed amounts prepared are shown in Table 1, and all values are expressed in parts by weight. In Examples 1 to 5, component (C) was dissolved in component (D) in advance to form an aqueous solution, which was then mixed.

<Component (A)>
a1: Bisphenol A type epoxy resin (jER828 manufactured by Mitsubishi Chemical Corporation)
<Component (B)>
b1: Amine-based curing agent having a viscosity of 1700 mPa·s at 25° C. and an amine value of 365 KOHmg/g (ST12 manufactured by Mitsubishi Chemical Corporation)
<Component (C)>
c1: Sodium hydroxide (reagent)
c2: Potassium hydroxide (reagent)
<Component (D)>
d1: Ion-exchanged water (component (E))
e1: 3-glycidoxypropyltrimethoxysilane (KBM-403, manufactured by Shin-Etsu Chemical Co., Ltd.)

The test methods used in the examples and comparative examples in Table 1 are as follows.

<(1) AL/AL tensile shear adhesive strength test (initial stage)>
The A agent and B agent shown in Table 1 were prepared, and 50 parts by mass of B agent were mixed with 100 parts by mass of A agent to prepare a mixed resin composition. Next, the mixed resin composition was applied to an aluminum test piece having a width of 25 mm, a length of 100 mm, and a thickness of 1.0 mm. Then, another aluminum test piece having a width of 25 mm, a length of 100 mm, and a thickness of 1.0 mm was attached so that the overlapping surface was 25 mm x 10 mm, and fixed with a clip. Then, the test piece was cured for 30 minutes in a hot air drying oven set at 120°C to obtain a test piece. Then, the maximum shear bond strength (unit: MPa) was measured according to JIS K 6850 at 25°C using a universal tensile tester (tensile speed: 10 mm/min.) using the test piece. The results are shown in Table 1. In the present invention, 10 MPa or more is preferable, and more preferably 12 MPa or more. In the table, "evaluation impossible" means that the (C) component was not dissolved in the entire composition and therefore could not be evaluated.

<(2) AL/AL tensile shear adhesive strength test after 85°C x 85% RH high temperature and high humidity environmental test>
The A agent and B agent shown in Table 1 were prepared, and 50 parts by mass of B agent were mixed with 100 parts by mass of A agent to prepare a mixed resin composition. Next, the mixed resin composition was applied to an aluminum test piece having a width of 25 mm, a length of 100 mm, and a thickness of 1.0 mm. Then, another aluminum test piece having a width of 25 mm, a length of 100 mm, and a thickness of 1.0 mm was attached so that the overlap surface was 25 mm x 10 mm and fixed with a clip. Then, the test piece was cured for 30 minutes in a hot air drying oven set at 120°C to obtain a test piece. Then, each test piece was placed in a high-temperature and high-humidity chamber set at 85°C x 85% RH for 240 hours, and then removed from the high-temperature and high-humidity chamber and left at room temperature for 1 hour. Then, the maximum shear adhesive strength (unit: MPa) was measured according to JIS K 6850 using a universal tensile tester (tensile speed: 10 mm/min.) at 25°C using the test piece. The results are shown in Table 1.
In the present invention, from the viewpoint of reliability, the pressure is preferably 16 MPa or more, more preferably 18 MPa or more, and particularly preferably 19 MPa or more. In the table, "evaluation not possible" means that the component (C) was not dissolved in the entire composition and therefore could not be evaluated.

Examples 1 to 5 in Table 1 show that the present invention can provide an epoxy resin adhesive composition that has excellent adhesive strength after a high-temperature, high-humidity environmental test at 85°C and 85% RH.

In addition, Comparative Example 1 in Table 1 is a composition that does not contain the components (C) and (D) of the present invention, but the adhesive strength after the high temperature and high humidity environment test was poor. In addition, Comparative Example 2 is a composition that does not contain component (C), so component (C) did not dissolve in the entire composition, making it impossible to evaluate.

Furthermore, (3) a Zn/Zn tensile shear bond strength test after a high temperature and high humidity environment test at 85°C x 85% RH and (4) a storage stability confirmation test were performed.

<(3) Zn/Zn tensile shear adhesive strength test after 85°C x 85% RH high temperature and high humidity environmental test>
Agent A and agent B of Examples 1 and 4 and Comparative Example 1 in Table 1 were prepared, and 50 parts by mass of agent B were mixed with 100 parts by mass of agent A to prepare a mixed resin composition. Next, the mixed resin composition was applied to a zinc test piece having a width of 25 mm, a length of 100 mm, and a thickness of 1.0 mm. Then, another zinc test piece having a width of 25 mm, a length of 100 mm, and a thickness of 1.0 mm was attached so that the overlap surface was 25 mm x 10 mm and fixed with a clip. Then, the test piece was cured for 30 minutes in a hot air drying oven set at 120°C to obtain a test piece. Then, each test piece was placed in a high-temperature, high-humidity chamber set at 85°C x 85% RH for 240 hours, and then removed from the high-temperature, high-humidity chamber and left at room temperature for 1 hour. Then, the maximum shear adhesive strength (unit: MPa) was measured according to JIS K 6850 using a universal tensile tester (tensile speed: 10 mm/min.) at 25°C. In the present invention, from the viewpoint of reliability, the adhesive strength is preferably 3 MPa or more, more preferably 4 MPa or more, and particularly preferably 5 MPa or more. The results were 4.8 MPa for Example 1, 5.5 MPa for Example 4, and 2.7 MPa for Comparative Example 1. From these results, it was confirmed that the epoxy resin adhesive composition according to the present invention has excellent adhesive strength not only to aluminum but also to zinc under high temperature and high humidity conditions, and therefore it was found to be effective for amphoteric metals in general.

<(4) Storage stability confirmation test>
After storing the A and B agents of Example 1 in Table 1 at 25°C for 2 months, a test similar to the AL/AL tensile shear adhesive strength test after the 85°C x 85% RH high temperature and high humidity environment test (1) was carried out. In the present invention, from the viewpoint of reliability, 16 MPa or more is preferable, more preferably 18 MPa or more, and particularly preferably 19 MPa or more. The result of Example 1 was 19.8 MPa, which did not change from the initial state. Therefore, it was confirmed that the present invention has excellent storage stability.

The present invention is an epoxy resin adhesive composition that has excellent adhesive strength after a high-temperature, high-humidity environmental test at 85°C x 85% RH, and can be used for a variety of adhesive applications. It is particularly useful industrially as an adhesive for infrastructure parts that are left in outdoor environments for long periods of time.

Claims (11)

An epoxy resin adhesive composition comprising the following components (A) to (D):
Component (A): epoxy resin Component (B): hardener that reacts with epoxy resin Component (C): alkali metal hydroxide Component (D): water The epoxy resin adhesive composition according to claim 1, wherein the component (C) is sodium hydroxide or potassium hydroxide. The epoxy resin adhesive composition according to claim 1 or 2, further comprising a silane coupling agent as component (E). The epoxy resin adhesive composition according to claim 1 or 2, in which the amount of the (C) component is 0.001 to 40 parts by mass per 100 parts by mass of the (B) component. The epoxy resin adhesive composition according to claim 1 or 2, wherein the component (A) contains a bisphenol-type epoxy resin. The epoxy resin adhesive composition according to claim 1 or 2, wherein the component (B) contains a polyamine compound having an amine value of 200 to 700 KOHmg/g. The epoxy resin adhesive composition according to claim 1 or 2, which is used on an adherend made of an amphoteric metal. The epoxy resin adhesive composition according to claim 7, wherein the amphoteric metal is aluminum or zinc. A two-component epoxy resin adhesive composition comprising the following components A and B:
Component A: (A) a composition containing an epoxy resin Component B: a composition containing the following components (B) to (D) Component (B): a curing agent that reacts with an epoxy resin Component (C): an alkali metal hydroxide Component (D): water The two-part epoxy resin adhesive composition according to claim 9, further comprising a silane coupling agent as component (E) in component A or component B. A cured product obtained by curing either the epoxy resin adhesive composition according to claim 1 or the two-component epoxy resin adhesive composition according to claim 9.