JP2010270198A - Epoxy resin composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an epoxy resin composition preferably usable as a structural adhesive which can achieve good adhesive strength in a wide temperature range from a low temperature (about -20°C) to a high temperature (about 80°C) and ensures reliability in adhesion. <P>SOLUTION: The epoxy resin composition comprises an epoxy resin (A), core-shell type rubber particles (B) and a hollow polymer (C). <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an epoxy resin composition.

  Structural adhesives can bond dissimilar materials, can disperse stress uniformly, have a sealing effect, have a smooth surface and good aesthetics, have electrical insulation, and have excellent adhesion durability. Because of its superior or extraordinary effects compared to welding, rivets, bolts, etc., it is used as an alternative or in combination with them to bond structural parts such as automobiles and aircraft. .

  For example, in a part such as an automobile roof rail and various billers, a construction method (weld bond construction method) using spot welding and an adhesive is employed for the purpose of securing vehicle body rigidity and strength.

  In addition, for example, a part called an opening (lid) such as an automobile hood, door, or trunk lid is basically composed of an outer plate (outer panel) and an inner plate (inner panel). The part employs a caulking structure called “hemming” over almost the entire circumference, and a structural adhesive is used to bond the hemming part.

  When driving an automobile, the joints where the weld bond method is used and the hemming part are exposed to a low temperature of about −20 ° C. to a high temperature of about 80 ° C., and stress is concentrated without being dispersed. There is.

  Therefore, it is desirable that the structural adhesive has high adhesive performance in a wide temperature range from a low temperature (about −20 ° C.) to a high temperature (about 80 ° C.).

As a thing relevant to a structural adhesive agent, the thing of patent document 1 is mentioned, for example.
In Patent Document 1, (A) a specific epoxy resin, (B) a core / shell type powdery polymer having a core / shell two-layer structure, and (C) a thermally activated curing agent are essential components. An epoxy resin-based adhesive composition having pseudo-curing characteristics is described. It is described that such a composition has characteristics such as excellent resistance to impact, adhesion properties such as tensile shear strength and T-peel strength, and good pseudo-curability.

JP-A-5-214310

  However, although the adhesive containing the core-shell type powder having a two-layer structure described in Patent Document 1 has sufficient adhesive strength from low temperature to normal temperature, the adhesive strength at high temperature of about 80 ° C. is not sufficient.

  Further, it is not appropriate to evaluate the adhesive performance only by “adhesion strength”, and it is evaluated in consideration of “destruction mode”. For example, when an adhesive strength test is performed using a plated steel sheet as an adherend, “cohesive failure” is preferred, in which the inside of the adhesive layer is destroyed, but “interfacial fracture” occurs at the interface between the adhesive and the plated steel sheet. "Or" material (plating) destruction "in which plating is peeled off from the steel sheet is a state in which the adhesive force cannot be controlled, and the reliability of adhesion is poor, which is not preferable.

  Therefore, the present invention can obtain a good adhesive strength in a wide temperature range from a low temperature (about −20 ° C.) to a high temperature (about 80 ° C.), and the adhesion is reliable, resulting in plating failure. It is an object of the present invention to provide an epoxy resin composition that can be preferably used as a structural adhesive.

The present invention includes the following (1) to (10).
(1) An epoxy resin composition comprising an epoxy resin (A), core-shell rubber particles (B), and a hollow polymer (C).
(2) The epoxy resin composition according to (1), further comprising a curing agent (D).
(3) The epoxy resin composition according to (1) or (2), wherein the core-shell type rubber particles (B) have three layers of a core layer, an intermediate layer, and a shell layer.
(4) The epoxy resin composition according to (3), wherein the shell layer has a glass transition temperature of 50 ° C. or higher.
(5) The epoxy resin composition according to any one of (1) to (4), wherein the hollow polymer (C) has an average particle size of 10 to 100 μm.
(6) The epoxy resin composition according to any one of (1) to (5), wherein the polymer component of the hollow polymer (C) has an acrylonitrile group.
(7) 10-100 parts by mass of the core-shell rubber particles (B) and 0.1-10 parts by mass of the hollow polymer (C) with respect to 100 parts by mass of the epoxy resin (A). The epoxy resin composition according to any one of 1) to (6).
(8) The epoxy resin composition according to any one of (1) to (7), which is a structural adhesive.
(9) A structural adhesive comprising the epoxy resin composition according to any one of (1) to (7).
(10) An automobile having a member bonded using the structural adhesive according to (9).

  According to the present invention, it can be preferably used as an epoxy resin composition and a structural adhesive excellent in adhesive performance in a wide temperature range from a low temperature (about −20 ° C.) to a high temperature (about 80 ° C.). Here, the “structural adhesive” is “adhesive with little adhesive property degradation and high adhesion reliability even when a large load is applied for a long time” (JIS K 6800).

The present invention is an epoxy resin composition containing an epoxy resin (A), core-shell rubber particles (B), and a hollow polymer (C).
Such an epoxy resin composition may be simply referred to as “the composition of the present invention” in the present specification.

The present invention is described in detail below.
1. Epoxy resin (A)
The epoxy resin (A) can be used without any particular limitation as long as it is a compound having two or more epoxy groups in the molecule. Moreover, such a compound can be used individually by 1 type or in combination of 2 or more types.
For example, epoxy compounds having a bisphenyl group such as bisphenol A type, bisphenol F type, brominated bisphenol A type, hydrogenated bisphenol A type, bisphenol S type, bisphenol AF type, biphenyl type, polyalkylene glycol type, alkylene glycol Type epoxy compound, bifunctional glycidyl ether type epoxy resin such as epoxy compound having naphthalene ring, epoxy compound having fluorene group; phenol novolak type, orthocresol novolak type, trishydroxyphenylmethane type, tetraphenylolethane type Polyfunctional glycidyl ether type epoxy resin such as diglyceryl ester type epoxy resin of synthetic fatty acid such as dimer acid; N, N, N ′, N′-tetraglycidyl diaminodipheny Aromatic epoxy resin having glycidylamino group such as methane (TGDDM), tetraglycidyl-m-xylylenediamine, triglycidyl-p-aminophenol, N, N-diglycidylaniline; epoxy compound having tricyclodecane ring (For example, an epoxy compound obtained by a production method in which dicyclopentadiene and cresols such as m-cresol or phenols are polymerized and then reacted with epichlorohydrin) can be used. Or two or more types can be used in combination.

  The epoxy resin (A) is preferably used in combination of a bisphenol A type epoxy resin and / or a bisphenol F type epoxy resin and a urethane modified epoxy resin and / or a rubber modified epoxy resin. This is because, when combined, the adhesive strength increases, and the adhesive reliability can be improved by controlling the adhesive force. In the epoxy resin (A), the urethane-modified epoxy resin and / or the rubber-modified epoxy resin is preferably 10 to 70% by mass, the urethane-modified epoxy resin is 5 to 40% by mass, and the rubber-modified epoxy resin is 5 to 50%. More preferably, it is mass%. This is because the adhesive strength is improved when the blending amount is within this range.

(1.1) Bisphenol A type epoxy resin The bisphenol A type epoxy resin preferably has an epoxy equivalent in the range of 180 to 300 g / eq, and is used alone or in combination of two or more. be able to.
Specific examples of the bisphenol A type epoxy resin include, for example, jER series (827, 828, 834, etc.) manufactured by Japan Epoxy Resin, Epiklon series (840, 850, etc.) manufactured by DIC, Adeka Resin EP- manufactured by ADEKA It can be used by appropriately selecting from 4100 series or the like.

(1.2) Bisphenol F-type epoxy resin The bisphenol F-type epoxy resin preferably has an epoxy equivalent in the range of 150 to 200 g / eq, and is used alone or in combination of two or more. be able to.
Specific examples of the bisphenol F type epoxy resin include, for example, jER series (806, 807, etc.) manufactured by Japan Epoxy Resin, Epiklon series (830, 835, etc.) manufactured by DIC, and Adeka Resin EP-4900 series manufactured by ADEKA. It can be used by appropriately selecting from the above.

(1.3) Urethane-modified epoxy resin The urethane-modified epoxy resin is not particularly limited as long as it has a urethane bond and two or more epoxy groups in the molecule.
Urethane-modified epoxy resins can be used alone or in combination of two or more.
Specifically, as the urethane-modified epoxy resin, for example, it is appropriately selected from the Mitsui Chemicals Epoxy series (803, 802-30CX, 820-40CX, 834, etc.), the ADEKA Resin EPU series, etc. be able to.

(1.4) Rubber-modified epoxy resin The rubber-modified epoxy resin is not particularly limited as long as it has two or more epoxy groups in the molecule and the skeleton is rubber.
Examples of the rubber forming the skeleton include polybutadiene, acrylonitrile butadiene rubber (NBR), and carboxyl group-terminated NBR (CTBN).
One rubber-modified epoxy resin can be used alone, or two or more rubber-modified epoxy resins can be used in combination.
Specifically, the rubber-modified epoxy resin can be appropriately selected from, for example, EPR series manufactured by ADEKA.

2. Core-shell type rubber particles (B)
The core-shell type rubber particle (B) contained in the composition of the present invention is not particularly limited as long as it has a structure having at least three layers of a core layer, an intermediate layer and a shell layer, but a crosslinked rubber layer exhibiting rubber elasticity. Those having a structure in which (intermediate layer) is coated with a crosslinked polymer (shell layer) that does not exhibit rubber elasticity are preferred, and those having a glass transition point of 50 ° C. or higher of the core layer inside the crosslinked rubber layer are preferred. .
For example, when the core-shell rubber particles (B) are substantially spherical particles having a three-layer structure, the glass transition point is −30 ° C. so as to cover the core layer with a core layer having a glass transition point of 50 ° C. or more at the center. It has the following intermediate layer, and further has a shell layer on the outermost shell having a glass transition point of 50 ° C. or higher so as to cover the intermediate layer.
The core-shell type rubber particles (B) may have a structure of four layers or more. For example, a four-layer structure having a glass transition point of 50 ° C. or less inside the core layer may be used.

  It is preferable that the surface of the core-shell type rubber particle is modified with an epoxy group or a functional group reactive with the epoxy group. Examples of the functional group having reactivity with the epoxy group include a carboxyl group, a glycidyl group, a hydroxyl group, and an amino group.

  Moreover, it is preferable that it is 10-100 mass parts with respect to 100 mass parts of the said epoxy resin (A), and, as for a core-shell type rubber particle (B), it is more preferable that it is 20-100 mass parts. More preferably, it is 80 parts by mass. This is because the flexibility of the composition of the present invention is further increased and the strength as an adhesive is further sufficient.

  The core-shell type rubber particles (B) preferably have an average primary particle diameter of 50 nm to 500 nm, and more preferably 50 to 300 nm. This is because the core-shell type rubber particles hardly aggregate and workability is good. Moreover, it is because the adhesive strength of the composition of this invention increases more. The average primary particle diameter of the core-shell type rubber particles means a value obtained by measurement using a zeta potential particle size distribution analyzer (Beckman Coulter).

(2.1) Core layer The core layer is a portion existing near the center of the core-shell type rubber particles (B).
Although the substance which forms a core layer is not specifically limited, A glass transition temperature (Tg) 50 degreeC or more is preferable, The thing of the range of 50-200 degreeC is more preferable, The thing of the range of 80-200 degreeC is further more preferable. It is because the composition of this invention provided with adhesive force at higher temperature is obtained.
The glass transition temperature is the temperature at the peak value of tan δ in dynamic viscoelasticity measurement. The same applies to the glass transition temperatures in the intermediate layer and the shell layer.
The core layer is preferably made of a polymer obtained by polymerizing monomers of methyl methacrylate and / or styrene, or a polymer obtained by copolymerizing a monomer copolymerizable therewith.

  Examples of monomers copolymerizable with methyl methacrylate or styrene include alkyl acrylates such as ethyl acrylate and butyl acrylate, alkyl methacrylates such as ethyl methacrylate and butyl methacrylate, aromatic vinyl such as vinyl toluene and α-methyl styrene, aromatic vinylidene, and acrylonitrile. And vinyl polymerizable monomers such as vinyl cyanide such as methacrylonitrile and vinylidene cyanide. Of these, ethyl acrylate or acrylonitrile is preferred. Moreover, a monomer having a functional group such as an epoxy group, a carboxyl group, a hydroxyl group, or an amino group can be copolymerized. For example, the monomer having an epoxy group includes glycidyl methacrylate, and the monomer having a carboxyl group includes methacrylic acid, acrylic acid, maleic acid, and itaconic acid. Examples of the monomer having a hydroxyl group include 2-hydroxy methacrylate and 2-hydroxy acrylate.

Moreover, it is preferable to use a crosslinkable monomer or a grafting monomer within 10% by mass as a monomer copolymerizable with methyl methacrylate or styrene. This is because bonding between layers is obtained and the particles are hardly deformed even during heating.
Examples of the crosslinkable monomer include aromatic divinyl compounds such as divinylbenzene, alkane polyol polyacrylates such as hexanediol diacrylate and norbornene dimethylol dimethacrylate. Examples of the grafting monomer include unsaturated carboxylic acid allyl esters such as allyl methacrylate.

(2.2) Intermediate layer The intermediate layer is a layer existing outside the core layer.
The material forming the intermediate layer is not particularly limited, but preferably has a glass transition temperature of −30 ° C. or lower, more preferably −110 to −30 ° C., and −110 to −40 ° C. More preferably. This is because the elastic modulus at low temperature can be lowered and the peel strength can be increased.
In addition, when the core-shell type rubber particles (B) have a structure having four or more layers and there are two or more intermediate layers, at least one of the intermediate layers is made of a material having a glass transition temperature of −30 ° C. or less. Is preferred.

The intermediate layer is preferably made of a polymer obtained by polymerizing a conjugated diene and / or an alkyl acrylate having 2 to 8 carbon atoms of an alkyl group, or a polymer obtained by copolymerizing these with a copolymerizable monomer.
Examples of the conjugated diene include butadiene, isoprene, chloroprene, etc. Among them, butadiene is preferable.
Examples of the alkyl acrylate having 2 to 8 carbon atoms in the alkyl group include ethyl acrylate, propyl acrylate, butyl acrylate, cyclohexyl acrylate, and 2-ethylhexyl acrylate. Of these, butyl acrylate is preferable.

  Examples of monomers copolymerizable with conjugated dienes or alkyl acrylates include aromatic vinyl such as styrene, vinyl toluene, and α-methylstyrene, vinyl cyanide such as aromatic vinylidene, acrylonitrile, and methacrylonitrile, vinylidene cyanide, Examples include alkyl methacrylates such as methyl methacrylate and butyl methacrylate, and aromatic (meth) acrylates such as benzyl acrylate, phenoxyethyl acrylate, and benzyl methacrylate. Moreover, a monomer having a functional group such as an epoxy group, a carboxyl group, a hydroxyl group, or an amino group can be copolymerized. For example, the monomer having an epoxy group includes glycidyl methacrylate, and the monomer having a carboxyl group includes methacrylic acid, acrylic acid, maleic acid, and itaconic acid. Examples of the monomer having a hydroxyl group include 2-hydroxy methacrylate and 2-hydroxy acrylate.

Further, it is preferable to use a small amount of a crosslinkable monomer or a grafting monomer as a monomer copolymerizable with the conjugated diene or alkyl acrylate. This is because bonding between layers is obtained and the particles are hardly deformed even during heating.
Specifically, the crosslinkable monomer or grafting monomer that can be used for forming the core layer can be used within 10% by mass.

(2.3) Shell Layer The shell layer is an outermost shell layer that covers the intermediate layer, and is a layer for preventing aggregation of the core-shell type rubber particles.
Therefore, the material forming the shell layer is not particularly limited, but it is preferable that the glass transition point is a material having a glass transition temperature of 50 ° C. or higher, like the core layer. The same applies to preferable glass transition points, and the same applies to materials that can be preferably used.

3. Hollow polymer (C)
The hollow polymer (C) will be described below.
The hollow polymer used in the composition of the present invention is one in which the outer shell of a hollow sphere is composed of a resin. For example, a thermally expandable hollow polymer obtained by encapsulating a liquid inside the hollow polymer and heating it to expand the hollow polymer as an outer shell and vaporize the liquid inside is mentioned.

Examples of the material constituting the outer shell of the hollow polymer include phenol resin, urea resin, polystyrene resin, polyvinylidene chloride, and thermoplastic resin.
The material constituting the outer shell of the hollow polymer is preferably at least one selected from the group consisting of phenolic resin, urea resin, polystyrene, polyvinylidene chloride and thermoplastic resin.

Examples of the thermoplastic resin constituting the outer shell of the thermoplastic hollow polymer include vinyl chloride, vinylidene chloride; acrylonitrile, methacrylonitrile; acrylate compounds such as benzyl acrylate and norbornane acrylate; methyl methacrylate, norbornane methacrylate, and trimethylolpropane. Methacrylate compounds such as trimethacrylate; styrenic monomers; vinyl acetate; butadiene; vinyl pyridine; chloroprene homopolymers and copolymers thereof.
Among these, from the viewpoint of weather resistance and heat resistance, an acrylonitrile copolymer (for example, a copolymer of acrylonitrile and methacrylonitrile, a butadiene copolymerizable with acrylonitrile, a copolymer with a vinyl monomer such as styrene). ), Vinylidene chloride polymers are preferred.

Examples of the liquid included in the hollow polymer include hydrocarbons such as n-pentane, isopentane, neopentane, butane, isobutane, hexane, and petroleum ether; methyl chloride, methylene chloride, dichloroethylene, trichloroethane, trichloroethylene, and the like. A chlorinated hydrocarbon is mentioned.
The hollow polymer is not particularly limited for its production. For example, a conventionally well-known thing is mentioned.

The content of the hollow polymer is preferably 0.1 to 10 parts by mass, more preferably 1 to 10 parts by mass, and further preferably 3 to 10 parts by mass with respect to 100 parts by mass of the epoxy resin (A).
This is because when the content of the hollow polymer is within this range, mechanical stress can be uniformly dispersed after the resulting composition is cured, and the adhesive strength is excellent.

In the present invention, the average particle size of the hollow polymer is not particularly limited, but is preferably in the range of 10 to 100 μm.
The maximum particle diameter of the hollow polymer is not particularly limited as long as the hollow polymer used for general purposes has a range, preferably 600 μm or less, more preferably 500 μm or less.

  In the present invention, the particle size of the hollow polymer is measured using a Microtrac particle size distribution meter (manufactured by Nikkiso Co., Ltd.) as a measuring device based on the laser diffraction method.

In the present invention, a hollow polymer having a hollow polymer coated with an inorganic filler can be used.
From the viewpoint that the hollow polymer is excellent in handling during the production of the curing agent, it is mentioned as one of preferred embodiments that the hollow polymer is coated with an inorganic filler.
The inorganic filler used for coating the hollow polymer is not particularly limited. Examples include calcium carbonate, titanium oxide, silicon oxide, talc, clay, and carbon black.
The inorganic filler is preferably at least one selected from the group consisting of calcium carbonate, titanium oxide, silicon oxide, talc, clay, and carbon black from the viewpoint of excellent hollow polymer coating.
An inorganic filler can be used individually or in combination of 2 or more types, respectively.
The method for coating the hollow polymer with an inorganic filler is not particularly limited, and examples thereof include conventionally known methods.

  Specifically, for example, the hollow polymer (C) can be appropriately selected from the microsphere MFL series (manufactured by Matsumoto Yushi Co., Ltd.).

4). Curing agent (D) and others that may be blended The curing agent (D) contained in the composition of the present invention is not particularly limited, and those usually used as curing agents for epoxy resins can be used. For example, dicyandiamide, 4,4′-diaminodiphenylsulfone, imidazole derivatives such as 2-n-heptadecylimidazole, isophthalic acid dihydrazide, N, N-dialkylurea derivatives, N, N-dialkylthiourea derivatives, tetrahydrophthalic anhydride An acid anhydride such as, isophoronediamine, m-phenylenediamine, N-aminoethylpiperazine, melamine, guanamine, boron trifluoride complex compound, trisdimethylaminomethylphenol and the like can be used. Two or more of these may be used in combination.

  Moreover, content in the composition of this invention of a hardening | curing agent (D) is not specifically limited, The optimal quantity changes with kinds of hardening | curing agent. For example, the optimal amount for each curing agent known in the art can be preferably used. This optimum amount is described, for example, in Chapter 3 of “Review Epoxy Resin Basics” (Epoxy Resin Technical Association, published in 2003).

  In addition to the epoxy resin (A), the core-shell type rubber particles (B) and the hollow polymer (C), and optionally the curing agent (C), the composition of the present invention may further comprise a catalyst depending on the application. , Curing accelerators, inorganic fillers, organic or polymer fillers, flame retardants, antistatic agents, conductivity-imparting agents, lubricants, slidability-imparting agents, surfactants, colorants and the like. Two or more of these may be contained.

5. Manufacturing method The manufacturing method of the composition of this invention is not specifically limited, For example, it can manufacture by a conventionally well-known method. For example, the epoxy resin (A), the core-shell type rubber particles (B), the hollow polymer (C), the curing agent (D) and, if necessary, other components such as a curing accelerator are kneaded uniformly at room temperature. Obtainable.

Hereinafter, the present invention will be specifically described with reference to examples. However, the present invention is not limited to these.
(Examples 1-9)
<I. Composition>
<< 1. Epoxy resin (A) >>
(1) Epoxy resin 1 bisphenol A type epoxy resin (jER828, manufactured by Japan Epoxy Resin Co., Ltd.)
(2) Epoxy resin 2 ... urethane-modified epoxy resin (Adeka Resin EPU-78-11, manufactured by ADEKA)
(3) Epoxy resin 3 ... rubber-modified epoxy resin (Adeka Resin EPR-1309, manufactured by ADEKA)
<< 2. Core-shell type rubber particles (B) >>
(1) Core-shell type rubber particles 1... Three-layer structure core-shell type rubber particles (IM-601, manufactured by Ganz Kasei Co., Ltd .: average particle size of primary particles = 200 to 300 nm, shell: acrylonitrile-styrene)
(2) Core-shell type rubber particle 2... In which methacrylic acid is introduced into the surface layer of the core-shell type rubber particle 1 (average particle size of primary particles = 200 to 300 nm)
<< 3. Hollow polymer (C) >>
(1) Hollow polymer 1 ... Microsphere MFL-60cask (average particle size 50-60 μm, manufactured by Matsumoto Yushi Co., Ltd.)
(2) Hollow polymer 2 ... Microsphere MFL-100L (average particle size 30 μm, manufactured by Matsumoto Yushi Co., Ltd.)
<< 4. Hardener (C) and other ingredients >>
As the curing agent (C) and other components, the following were used.
(1) Curing agent (C): jER cure DICY15 (dicyandiamide finely pulverized product, manufactured by Japan Epoxy Resin Co., Ltd.)
(2) Catalyst: DCMU99 (aromatic urea compound, manufactured by Hodogaya Chemical Co., Ltd.)
(3) Silica ... RY-200S (manufactured by Nippon Aerosil Co., Ltd.)
(4) Silane coupling agent: KBM-403 (3-glycidoxypropyltrimethoxysilane, manufactured by Shin-Etsu Chemical Co., Ltd.)
<< 5. Production method"
The above components were blended in amounts (parts by mass) of the components described in Table 1, and mixed uniformly with a mixer to obtain compositions of Examples 1 to 9 and Comparative Examples 1 and 2.

<II. Physical properties>
<< 1. Shear strength >>
Using a plated steel plate of 0.8 x 25 x 200 mm in size as the adherend, tensile shear in accordance with the test method of the standard (JIS K 6850: 1999) on the test method for tensile shear bond strength of rigid adherends The bond strength (shear strength) was determined for each of low temperature (−20 ° C.), room temperature (25 ° C.) and high temperature (80 ° C.) (unit: MPa). The test results are shown in Table 1. The failure mode is a failure mode at the time of a peeling test at 80 ° C., and the format listed in the standard (JIS K 6866: 1999) regarding the name of the main failure mode is described in Table 1 as an abbreviation (CF = aggregation). Failure, AF = interface failure, MF = material (plating) failure).
The shear strength was determined to be acceptable with 15.0 MPa as the reference.
<< 2. Peel strength
Peeling adhesion strength in accordance with the test method of JIS K 6854-3: 1999, using a plated steel plate of 0.8 x 25 x 200 mm in size as the adherend, and T-type peeling adhesion strength test method (Peeling strength) was determined for each of low temperature (−20 ° C.), room temperature (25 ° C.) and high temperature (80 ° C.) (unit: N / 25 mm). The test results are shown in Table 1. The failure mode is a failure mode at the time of a peeling test at 80 ° C., and the format listed in the standard (JIS K 6866: 1999) regarding the name of the main failure mode is described in Table 1 as an abbreviation (CF = aggregation). Failure, AF = interface failure, MF = material (plating) failure).
The peel strength was determined to be acceptable with 150 N / 25 mm as a reference.

<III. Evaluation>
<< 1. Example"
Examples 1 to 9 are test examples for an epoxy resin composition containing an epoxy resin (A), core-shell type rubber particles (B), and a hollow polymer (C).
In the shear test, the shear strength was 15.0 MPa or more under all conditions of −20 ° C., room temperature, and 80 ° C., and the fracture mode at 80 ° C. was “cohesive fracture (CF)”. In the peeling test, the peeling strength was 150 N / 25 mm or more under all conditions of −20 ° C., room temperature, and 80 ° C., and the breaking mode at 80 ° C. was “cohesive failure (CF)”.
In order to ensure that the adhesive and the adherend are bonded, the failure mode must be “cohesive failure”.
Therefore, the epoxy resin compositions according to Examples 1 to 9 have high adhesion reliability and solve the problems to be solved by the present invention.

<< 2. Comparative Example >>
Comparative Example 1 is an example in which the hollow polymer (C) was not blended.
In the shear test, although the shear strength was 15.0 MPa or more under all conditions of −20 ° C., room temperature, and 80 ° C., the fracture mode at 80 ° C. was “material (plating) fracture (MF)”. On the other hand, in the peeling test, the peeling strength was 150 N / 25 mm or more under all conditions of −20 ° C., room temperature and 80 ° C., and the breaking mode at 80 ° C. was “cohesive failure (CF)”.
In order to ensure that the adhesive and the adherend are bonded, the failure mode must be “cohesive failure”.
Therefore, the epoxy resin composition according to Comparative Example 1 has low adhesion reliability and does not solve the problem to be solved by the present invention.
Comparative Example 2 is an example in which the core-shell type rubber particles (B) were not blended.
In the shear test, although the shear strength was 15.0 MPa or more under all conditions of −20 ° C., room temperature, and 80 ° C., the fracture mode at 80 ° C. was “material (plating) fracture (MF)”. On the other hand, in the peel test, the peel strength was 150 N / 25 mm or more at −20 ° C. and room temperature, but the strength was clearly insufficient at 80 N / 25 mm at 80 ° C., and the fracture mode at 80 ° C. was “interface fracture ( AF) ".
In order to ensure that the adhesive and the adherend are bonded, the failure mode must be “cohesive failure”.
Therefore, the epoxy resin composition according to Comparative Example 2 has low adhesion reliability and does not solve the problem to be solved by the present invention.

<< 3. General >>
In Example 1, the shear strength at 80 ° C. was 26.5 MPa, and the fracture mode was CF. On the other hand, in Comparative Example 1, the shear strength at 80 ° C. was 25.0 MPa, and the fracture mode was MF.
From these results, it can be seen that, although Comparative Example 1 with a low shear strength resulted in MF, Example 1 with a higher shear strength than that resulted in CF unexpectedly.
This is because, in Example 1, the compounded hollow polymer was able to uniformly distribute the stress throughout the cured composition, whereas in Comparative Example 1, it was locally applied to a part of the composition. It can be explained that a large stress was applied and the peeling of the plating started from there.

  The epoxy resin composition of the present invention can be used, for example, as a structural adhesive for bonding structural members in the fields of automobiles, vehicles (bullet trains, trains), civil engineering, architecture, electronics, aircraft, and space industries.

Claims (7)

  An epoxy resin composition comprising an epoxy resin (A), core-shell rubber particles (B), and a hollow polymer (C).   The epoxy resin composition according to claim 1, wherein the core-shell type rubber particles (B) have three layers of a core layer, an intermediate layer, and a shell layer.   The epoxy resin composition according to claim 2, wherein the shell layer has a glass transition temperature of 50 ° C. or higher.   The epoxy resin composition in any one of Claims 1-3 whose average particle diameter of the said hollow polymer (C) is 10-100 micrometers.   The epoxy resin composition according to any one of claims 1 to 4, wherein the polymer component of the hollow polymer (C) has an acrylonitrile group.   Any one of Claims 1-5 which contain 10-100 mass parts of said core-shell type rubber particles (B) and 0.1-10 mass parts of said hollow polymers (C) with respect to 100 mass parts of said epoxy resins (A). An epoxy resin composition according to claim 1.   The epoxy resin composition according to claim 1, which is a structural adhesive.