JP4416046B1 - Epoxy resin composition and structural adhesive - Google Patents

Abstract

The present invention provides an epoxy resin composition that is excellent in adhesive performance and flexibility not only from a low temperature (about -20 ° C.) to a normal temperature but also at a high temperature (about 80 ° C.) and can be preferably used as a structural adhesive.
An epoxy resin composition mainly comprising an epoxy resin (A), core-shell particles (B) and a curing agent (C), wherein 1 to 50% by mass of the epoxy resin (A) is a urethane-modified epoxy. It is a resin, and the core-shell particle (B) has a structure having at least three layers of a core layer, an intermediate layer, and a shell layer, and the core-shell particle (B): 100 parts by mass of the epoxy resin (A): The epoxy resin composition which is 10-100 mass parts.
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Description

The present invention relates to an epoxy resin composition and a structural adhesive .

  Structural adhesives may require adhesive strength and flexibility at high temperatures as well as low temperatures.

  For example, in order to ensure vehicle body rigidity and strength in parts such as automobile roof rails and various billers, a method that uses spot welding and an adhesive (weld bond method) has been adopted. It is desirable that the adhesive used has a high adhesive strength to the steel plate at a high temperature of about 80 ° C. This is because parts such as roof rails and various billers may become hot when the automobile is running. Moreover, if the adhesive strength is high, the number of spots in spot welding can be reduced.

  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), and its end portion. Has adopted a caulking structure called “hemming” over almost the entire circumference, but it is desirable that the adhesive used for bonding the hemming portion has adhesive strength and flexibility at high temperatures. This is because the hemming part may become as high as about 80 ° C. when the automobile is running. In addition, when a load is applied to the bonding portion of the hemming portion, the stress is not dispersed and is easily concentrated at one point.

As what is related to such an adhesive, 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, the adhesive containing the core-shell type powder having a two-layer structure described in Patent Document 1 has a high strength at a low temperature to a normal temperature, but has a low strength at a high temperature of about 80 ° C.

  The present invention provides an epoxy resin composition that is excellent in adhesive performance and flexibility not only from low temperature (about −20 ° C.) to normal temperature but also at high temperature (about 80 ° C.) and can be preferably used as a structural adhesive. That is.

The present invention includes the following (1) to ( 3 ).
(1) An epoxy resin composition containing 60% by mass or more of the total of the epoxy resin (A), the core-shell particles (B), and the curing agent (C), and 1 to 50% by mass of the epoxy resin (A) Is a urethane-modified epoxy resin, and the core-shell particle (B) has a structure having at least three layers of a core layer, an intermediate layer, and a shell layer, and the core-shell particle with respect to 100 parts by mass of the epoxy resin (A) (B): 10 to 100 parts by mass der is, the glass transition point of the core layer in the core-shell particles (B) is not less 50 ° C. or higher, a glass transition point of the intermediate layer is at -30 ° C. or less, the Ru der glass transition point 50 ° C. or more shell layer, the epoxy resin composition.
( 2) The epoxy resin composition according to (1 ) above, wherein the average primary particle diameter of the core-shell particles (B) is 50 nm to 500 nm.
(3) (1) above or a structural adhesive comprising an epoxy resin composition according to (2).

  According to the present invention, there is provided an epoxy resin composition which is excellent in adhesive performance and flexibility not only from a low temperature (about −20 ° C.) to a normal temperature but also at a high temperature (about 80 ° C.) and can be preferably used as a structural adhesive. Can be provided.

The present invention will be described in detail.
The present invention is an epoxy resin composition mainly comprising an epoxy resin (A), core-shell particles (B) and a curing agent (C), wherein 1 to 50% by mass of the epoxy resin (A) is a urethane-modified epoxy. A resin having a structure in which the core-shell particle (B) has at least three layers of a core layer, an intermediate layer and a shell layer, and the core-shell particle (B): 100 parts by mass of the epoxy resin (A): It is an epoxy resin composition which is 10-100 mass parts.
Hereinafter, such an epoxy resin composition is also referred to as “the composition of the present invention”.
The “main component” means 60% by mass or more. That is, the total content of the epoxy resin (A), the core-shell particles (B), and the curing agent (C) in the composition of the present invention is 60% by mass or more. This ratio is preferably 70% by mass or more, and more preferably 80% by mass or more.

The epoxy resin (A) will be described.
As for the epoxy resin (A) which the composition of this invention contains, 1-50 mass% is a urethane-modified epoxy resin. That is, the epoxy resin (A) is a mixture of a urethane-modified epoxy resin and another epoxy resin. Other epoxy resins may consist of a plurality of types.

  As long as the urethane-modified epoxy resin (A) is a resin having a urethane bond and an epoxy group in the molecule, the structure is not particularly limited, but the urethane bond and the epoxy group are efficiently contained in one molecule. It can be obtained by reacting a urethane bond-containing compound (X) having an isocyanate group obtained by reacting a polyhydroxy compound and a polyisocyanate compound with a hydroxyl group-containing epoxy compound (Y). A resin is preferred.

  Examples of the polyhydroxy compound include polyether polyol and polyester polyol. Examples of the polyether polyol include low molecular weight polyhydric alcohols, amines, polyhydric phenols, compounds having two or more active hydrogens such as water, and initiators such as ethylene oxide, propylene oxide, and butylene oxide. A product obtained by addition polymerization of a cyclic ether such as alkylene oxide or tetrahydrofuran. Examples of the low molecular weight polyhydric alcohol include ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2- Examples include butanediol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, 1,6-hexanediol, hydrogenated bisphenol A, glycerin, trimethylolpropane, pentaerythritol, and the like. Is Anne Chloride, ethylenediamine, hexamethylenediamine, ethanolamine, propanolamine and the like. Examples of the polyhydric phenols resorcinol, hydroquinone, bisphenol A, bisphenol F, bisphenol S and the like.

Examples of the polyester polyol include condensates of the low molecular weight polyhydric alcohols or polyether polyols with polyvalent carboxylic acids, hydroxycarboxylic acids or carbonic acids, and ring-opening polymers of lactones. Examples of the polyvalent carboxylic acid include succinic acid, glutaric acid, adipic acid, sebacic acid, azelaic acid, maleic acid, phthalic acid, isophthalic acid, terephthalic acid, trimellitic acid, pyromellitic acid, and the like. Examples of the hydroxycarboxylic acid include 12-hydroxystearic acid and castor oil fatty acid, and examples of the lactone include ε-caprolactam.
As the polyhydroxy compound, an adduct of hydroxycarboxylic acid and alkylene oxide, polybutadiene polyol, polyolefin polyol or the like can also be used. Among these, when a polyether polyol is used, a cured product having excellent adhesion and flexibility is obtained, which is preferable. The molecular weight of the polyhydroxy compound is not particularly limited, but a weight average molecular weight in the range of 300 to 20000, particularly 1000 to 10,000 is used from the viewpoint of excellent balance between flexibility and curability. It is preferable. These chelate modifications are also included. Specific examples include EPU-78-11, EPU-1395, EPU-6E, and EPU-78-11S manufactured by ADEKA.

  Other than the urethane-modified epoxy resin constituting the epoxy resin (A), that is, “other epoxy resin” is not particularly limited as long as it has two or more epoxy groups. 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, epoxy compound having naphthalene ring, bifunctional glycidyl ether type epoxy resin such as epoxy compound having fluorene group; phenol novolak type, orthocresol novolak type, trishydroxyphenylmethane type, trifunctional type, tetra Polyfunctional glycidyl ether type epoxy resin such as phenylolethane type; Glycidyl ester type epoxy resin of synthetic fatty acid such as dimer acid; N, N, N ′, N′-tetraglycidyldiame Aromatic epoxy resins having a glycidylamino group such as diphenylmethane (TGDDM), tetraglycidyl-m-xylylenediamine, triglycidyl-p-aminophenol, N, N-diglycidylaniline; tricyclo [5.2.1. 02,6] decane ring-containing epoxy compounds (for example, epoxy compounds obtained by a production method in which dicyclopentadiene and cresols such as m-cresol or phenols are polymerized and then reacted with epichlorohydrin) .

  Other epoxy resins include, for example, epoxy resin having a sulfur atom in the epoxy resin main chain such as Flep 10 manufactured by Toray Fine Chemical Co .; polybutadiene, liquid polyacrylonitrile-butadiene rubber, acrylonitrile butadiene rubber (NBR) Such as bisphenol A type epoxy resin, bisphenol F type epoxy resin, sorbitol type epoxy resin, polyglycerol type epoxy resin, pentaerythritol type epoxy resin, trimethylolpropane type epoxy resin Examples thereof include an epoxy resin having an acetoacetate group.

The ratio of the urethane-modified epoxy resin in the epoxy resin (A) is 1 to 50% by mass, and preferably 2 to 30% by mass. If the amount is too small, the adhesion to the steel sheet is insufficient, and if it is too large, the adhesive strength decreases. The role of the urethane-modified epoxy is to impart flexibility to the steel plate interface by localizing a highly polar urethane-modified epoxy at the steel plate interface. The softening of the vicinity of the steel sheet interface is insufficient with the core shell alone, and high adhesive strength can be expressed by using urethane-modified epoxy and the core shell together.
In addition, in this invention, the ratio of the said urethane modified epoxy resin in an epoxy resin (A) shall be calculated | required from the addition amount of the said urethane modified epoxy resin at the time of manufacturing the composition of this invention.

The core-shell particles (B) will be described.
The core-shell particle (B) contained in the composition of the present invention has a structure having at least three layers of a core layer, an intermediate layer, and a shell layer, and a crosslinked rubber layer (intermediate layer) exhibiting rubber elasticity is provided with rubber elasticity. It is preferable that the glass transition point of the core layer on the inner side of the crosslinked rubber layer is 50 ° C. or higher.
For example, when the core-shell particle (B) is a substantially spherical particle having a three-layer structure, it has a core layer having a glass transition point of 50 ° C. or higher at the center and a glass transition point of −30 ° C. or lower so as to cover the core layer. And 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 particle (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.

Each layer constituting the core-shell particles (B) will be described.
First, the core layer will be described.
As described above, the core layer is a portion that exists in the vicinity of the center of the core-shell particle (B).
Although the substance which forms a core layer is not specifically limited, It is preferable that it is a substance whose glass transition point is 50 degreeC or more. The temperature is more preferably 50 to 200 ° C, and further preferably 80 to 200 ° C. It is because the composition of this invention provided with adhesive force at higher temperature is obtained.
The glass transition point is the temperature of the peak value of tan δ in dynamic viscoelasticity measurement. The same applies to the glass transition points 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 wt% 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.

Next, the intermediate layer will be described.
The intermediate layer is a layer existing outside the core layer.
Although the substance which forms an intermediate | middle layer is not specifically limited, It is preferable that it is a substance whose glass transition point is -30 degrees C or less. The temperature is more preferably −110 to −30 ° C., and further preferably −110 to −40 ° C. 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 particle (B) has a structure having four or more layers and there are two or more intermediate layers, it is preferable that at least one of the intermediate layers is made of a material having a glass transition point of −30 ° C. or lower. .

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 vinyls such as styrene, vinyl toluene, and α-methylstyrene, vinyl cyanides 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 a conjugated diene or an 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 wt%.

Next, the shell layer will be described.
As described above, the shell layer is an outermost shell layer that covers the intermediate layer, and is a layer for preventing aggregation of the core-shell particles.
Therefore, the material forming the shell layer is not particularly limited, but it is preferable that the glass transition point is 50 ° C. or higher as in the case of the core layer. The same applies to preferable glass transition points, and the same applies to materials that can be preferably used.

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

  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 particle (B), it is more preferable that it is 20-100 mass parts, and 25-80 masses. More preferably, it is a part. 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 particle (B) can be produced according to a known method for producing a general core-shell polymer. For example, it can be produced by sequentially forming a core layer, an intermediate layer and a shell layer by adding a predetermined monomer to the reaction system stepwise in accordance with a known seed polymerization method.

Next, the curing agent (C) will be described.
The hardening | curing agent (C) which the composition of this invention contains is not specifically limited, What is normally used as a hardening | curing agent of an epoxy resin 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 (C) is not specifically limited, The optimal amount 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 particles (B), and the curing agent (C), the composition of the present invention may further include a curing accelerator, an inorganic filler, an organic or polymer filling, depending on the application. An agent, a flame retardant, an antistatic agent, a conductivity imparting agent, a lubricant, a slidability imparting agent, a surfactant, a colorant and the like can be contained. Two or more of these may be contained.

  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 particles (B), the curing agent (C) and, if necessary, other components such as a curing accelerator can be obtained by uniformly kneading at room temperature.

  The composition of the present invention is excellent in adhesion performance and flexibility not only from a low temperature (about −20 ° C.) to a normal temperature but also at a high temperature (about 80 ° C.). Therefore, the composition of the present invention can be preferably used as a structural adhesive. Here, the “structural adhesive” is a highly reliable adhesive (JIS K6800) with little deterioration in adhesive properties even when a large load is applied for a long time. For example, it can be used for bonding structural members in the fields of automobiles, vehicles (bullet trains, trains), civil engineering, architecture, electronics, aircraft, and space industries.

Hereinafter, the present invention will be specifically described with reference to examples. However, the present invention is not limited to these.
(Examples 1-9)
As epoxy resin (A), bisphenol A type epoxy resin (JER828, manufactured by Japan Epoxy Resin Co., Ltd.), urethane modified epoxy resin (EPU-78-11, manufactured by ADEKA) and rubber modified epoxy resin (EPR-1309, manufactured by ADEKA) 3 core-shell particles (I) (IM-601, manufactured by Ganz Kasei Co., Ltd .: average particle size of primary particles = 200 to 300 nm, shell: acrylonitrile-styrene) or three-layer core shell Particle (II) (IM-602, manufactured by Ganz Kasei Co., Ltd .: average particle diameter of primary particles = 200 to 300 nm, shell: methyl methacrylate) is used as a curing agent (Dic15, manufactured by Japan Epoxy Resin Co., Ltd.) And a catalyst (DUMU99, manufactured by Hodogaya Chemical Co., Ltd.) and (RY-200S, Nippon Aerosil Co., Ltd.) was added to give them a composition uniformly kneaded to the present invention. The addition amount (part by mass) of each component in each example is as shown in Table 1.
And each composition was apply | coated to the surface of a non-plated steel plate, and it used for the tensile shear strength test and the T-shaped peel strength test. Here, both tests were conducted according to JIS K-6850 (1999). The test piece (non-plated steel plate) used was 0.8 × 25 × 200 mm. The test results are shown in Table 1.

(Comparative Example 1)
An experiment similar to that of Example 1 was performed except that the urethane-modified epoxy resin used in Example 1 was not used and 50 parts by mass of a rubber-modified epoxy resin was used instead. The test results are shown in Table 1.

(Comparative Example 2)
Example except that two-layer core-shell particles (AC-3355, manufactured by Ganz Kasei Co., Ltd .: average particle diameter of primary particles = 400 to 500 nm) were used instead of the three-layer core-shell particles used in Example 3. An experiment similar to 3 was performed. The test results are shown in Table 1.

In Examples 1 to 9, the ratio of the urethane-modified epoxy resin to the total epoxy resin is 1 to 50% by mass, and the tensile shear strength and the T-shaped peel strength are any of −20 ° C., room temperature, and 80 ° C. It was good.
Moreover, the fracture | rupture form in the T-shaped peel strength test in 80 degreeC was a cohesive fracture in any Example. Therefore, the reliability as an adhesive is high.
The breakdown includes “cohesive failure” in which the inside of the adhesive layer breaks and “interface failure” in which peeling occurs at the interface between the adhesive and the adherend (steel material). Here, also in order to ensure that the adhesive and the adherend are adhered, cohesive failure is preferred as the failure mode. Interfacial fracture is a condition in which the adhesive force cannot be controlled and is not reliable.
In Examples 7 to 9, even though it was almost cohesive failure, interfacial failure was also mixed. The description of “cohesive failure 70%” in Example 7 in the table means that two failure modes are mixed and interface failure is mixed 30 area%. The same applies to Examples 8 and 9.

On the other hand, when the composition of the comparative example 1 which does not contain a urethane-modified epoxy resin was used, it became low intensity | strength with respect to Examples 1-9. In particular, the strength at a high temperature (80 ° C.) was low as compared with Examples 1-9. Further, the fracture mode in the T-peel strength test at 80 ° C. was interface fracture. Therefore, the reliability as an adhesive is low.
Moreover, when the composition of Comparative Example 2 using a two-layer core shell was used, the strength was lower than that of Examples 1 to 9 as in Comparative Example 1. In particular, the strength at a high temperature (80 ° C.) was low as compared with Examples 1-9.

Claims (3)

An epoxy resin composition containing a total of 60% by mass or more of the epoxy resin (A), the core-shell particles (B), and the curing agent (C),
1 to 50% by mass of the epoxy resin (A) is a urethane-modified epoxy resin,
The core-shell particle (B) has a structure having at least three layers of a core layer, an intermediate layer, and a shell layer,
The epoxy resin (A): with respect to 100 parts by weight, the core-shell particles (B): Ri 10-100 parts by der,
The glass transition point of the core layer in the core-shell particles (B) is at 50 ° C. or more, the a glass transition point of the intermediate layer is -30 ° C. or less, Ru der glass transition point 50 ° C. or higher of the shell layer, Epoxy resin composition. The average primary particle diameter of the core-shell particles (B) is 50 nm~500 nm, epoxy resin composition according to claim 1. Structural adhesive comprising an epoxy resin composition according to 請 Motomeko 1 or 2.