JP2010185034A - Structural adhesive composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a structural adhesive composition having excellent adhesion performance and flexibility not only at a temperature from low (about -20°C) to room temperature but also at a high temperature (about 80°C). <P>SOLUTION: The structural adhesive composition includes an epoxy resin (A), rubber particles (B), and a curing agent (C) as major components and has a composition so as to have a storage modulus after curing of 1.0 GPa or less at -20°C and 0.2-0.7 GPa at 80°C. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a structural adhesive composition.

  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 pillars, a method that combines 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 pillars 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.

  Examples of such adhesives include an epoxy resin-based adhesive composition described in Patent Document 1 and a structural adhesive composition described in Patent Document 2.

JP-A-5-214310 JP 2005-272647 A

  However, the inventors of the present application have found that the adhesives described in Patent Documents 1 and 2 have high strength at low temperatures to normal temperatures, but the strength at high temperatures of about 80 ° C. decreases.

  An object of the present invention is to provide a structural adhesive composition that is excellent in adhesion performance and flexibility not only from low temperature (about −20 ° C.) to normal temperature but also at high temperature (about 80 ° C.).

The present invention includes the following (i) to (ii).
(I) It contains an epoxy resin (A), rubber particles (B) and a curing agent (C) as main components, and a storage elastic modulus after curing is 1.0 GPa or less at −20 ° C. and 0.2 to 80 ° C. A structural adhesive composition having a composition of 0.7 GPa.
(Ii) The structural adhesive composition according to (i) above, wherein the rubber particles (B) are core-shell type particles (B ′).

  ADVANTAGE OF THE INVENTION According to this invention, the structural adhesive composition which is excellent in adhesive performance and a softness | flexibility not only at normal temperature from low temperature (about -20 degreeC) but high temperature (about 80 degreeC) can be provided.

The present invention will be described in detail.
The present invention comprises an epoxy resin (A), rubber particles (B) and a curing agent (C) as main components, and has a storage elastic modulus of 1.0 GPa or less at −20 ° C. and 0.2 at 80 ° C. after curing. It is a structural adhesive composition having a composition of ˜0.7 GPa.
Hereinafter, the structural adhesive composition of the present invention is also referred to as “the composition of the present invention”.
In the composition of the present invention, the “main component” means 50% by mass or more. That is, the total content of the epoxy resin (A), the rubber particles (B) and the curing agent (C) in the composition of the present invention is 50% by mass or more, preferably 70% by mass or more, and 80% by mass. % Or more is more preferable.

The composition of the present invention is a composition having a composition in which the storage elastic modulus after curing is in a specific range (1.0 GPa or less at −20 ° C. and 0.2 to 0.7 GPa at 80 ° C.). The present inventor has repeatedly investigated and studied the properties of adhesive compositions having various compositions, and adjusted the composition so that the storage elastic modulus after curing is within the specific range. The present invention was completed by finding that a structural adhesive composition excellent in adhesive performance and flexibility is obtained not only at room temperature but also at high temperature (about 80 ° C.).
In the present invention, the storage elastic modulus is maintained at 170 ° C. for 30 minutes to cure the composition of the present invention, and thereafter, under the conditions of a heating rate of 5 ° C./min, a measurement frequency of 1 Hz, and a strain of 0.01%. The value obtained by the DMA measurement is meant.

The epoxy resin (A) will be described.
The epoxy resin (A) contained in the composition of the present invention is not particularly limited as long as it is a compound having 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, 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 of reacting epichlorohydrin after polymerizing cresols or phenols such as dicyclopentadiene and m-cresol) and the like.

Examples of the epoxy resin (A) include an epoxy resin having a sulfur atom in the epoxy resin main chain such as Flep 10 manufactured by Toray Fine Chemical Co., Ltd .; rubber-modified epoxy resin; urethane-modified epoxy resin.
An epoxy resin (A) can be used individually or in combination of 2 types or more, respectively.

  The epoxy resin (A) is preferably selected from the group consisting of bisphenol A type epoxy resins, bisphenol F type epoxy resins, rubber-modified epoxy resins and urethane-modified epoxy resins. This is because it is easy to obtain a composition having a storage elastic modulus after curing of 1.0 GPa or less at −20 ° C. and 0.2 to 0.7 GPa at 80 ° C.

  The bisphenol A type epoxy resin and the bisphenol F type epoxy resin preferably have an epoxy equivalent of 180 or more and 300 or less. The amount of the bisphenol A type epoxy resin and the bisphenol F type epoxy resin having an epoxy equivalent of 180 to 300 is preferably 0 to 100% by mass, and 0 to 70% by mass in the epoxy resin (A). Is more preferable. This is because in such a case, it is easy to obtain a composition having a storage elastic modulus after curing of 1.0 GPa or less at −20 ° C. and 0.2 to 0.7 GPa at 80 ° C.

The rubber-modified epoxy resin is not particularly limited as long as it is an epoxy resin having two or more epoxy groups and a skeleton of rubber. Examples of the rubber forming the skeleton include polybutadiene, acrylonitrile butadiene rubber (NBR), and carboxyl group-terminated NBR (CTBN). The rubber-modified epoxy resins can be used alone or in combination of two or more.
The rubber-modified epoxy resin preferably has an epoxy equivalent of 200 to 350 g / eq. Moreover, it is preferable that it is 0-100 mass% in an epoxy resin (A), and, as for the quantity of a rubber modified epoxy resin, it is more preferable that it is 0-60 mass%. This is because it is easy to obtain a composition having a storage elastic modulus after curing of 1.0 GPa or less at −20 ° C. and 0.2 to 0.7 GPa at 80 ° C.

The rubber-modified epoxy resin is not particularly limited for its production. For example, it can be produced by reacting rubber and epoxy in a large amount of epoxy. The epoxy (for example, epoxy resin) used when producing the rubber-modified epoxy resin is not particularly limited. For example, a conventionally well-known thing is mentioned.
In the present invention, the epoxy equivalent of the rubber-modified epoxy resin and the amount of addition thereof indicate the amount as the “rubber-modified epoxy resin containing the epoxy” because of the excess epoxy resin used in the production.

  The structure of the urethane-modified epoxy resin is not particularly limited as long as it is a resin having a urethane bond and two or more epoxy groups in the molecule. From the point that a urethane bond and an epoxy group can be efficiently introduced into one molecule, a urethane bond-containing compound (X) having an isocyanate group obtained by reacting a polyhydroxy compound and a polyisocyanate compound, and hydroxy A resin obtained by reacting the group-containing epoxy compound (Y) is preferable.

Examples of the polyhydroxy compound used in producing the urethane-modified epoxy resin include polyether polyols such as polypropylene glycol, polyester polyols, adducts of hydroxycarboxylic acid and alkylene oxide, polybutadiene polyols, and polyolefin polyols. It is done.
Especially, when a polyether polyol is used, it is easy to obtain a composition having a storage elastic modulus after curing of 1.0 GPa or less at −20 ° C. and 0.2 to 0.7 GPa at 80 ° C. It is.

  The molecular weight of the polyhydroxy compound is preferably in the range of 300 to 5000, particularly 500 to 2000 as the mass average molecular weight from the viewpoint of excellent balance between flexibility and curability.

  The polyisocyanate compound used when producing the urethane-modified epoxy resin is not particularly limited as long as it is a compound having two or more isocyanate groups. Examples thereof include aliphatic polymer isocyanates, aromatic polyisocyanates, and polyisocyanate groups having aromatic hydrocarbon groups. Of these, aromatic polyisocyanates are preferred. Examples of the aromatic polyisocyanate include tolylene diisocyanate, diphenylmethane diisocyanate, and naphthalene diisocyanate.

  By the above reaction, a urethane prepolymer containing a free isocyanate group at the terminal is obtained. This is reacted with an epoxy resin having at least one hydroxyl group in one molecule (for example, diglycidyl ether of bisphenol A, diglycidyl ether of bisphenol F, diglycidyl ether of aliphatic polyhydric alcohol and glycidol). A modified epoxy resin is obtained.

The urethane-modified epoxy resin preferably has an epoxy equivalent of 200 to 250 g / eq. This is because it is easy to obtain a composition having a storage elastic modulus after curing of 1.0 GPa or less at −20 ° C. and 0.2 to 0.7 GPa at 80 ° C.
The urethane-modified epoxy resins can be used alone or in combination of two or more.

  The amount of the urethane-modified epoxy resin is preferably 0 to 100% by mass, more preferably 0 to 50% by mass, and more preferably 1 to 50% by mass in the epoxy resin (A). It is more preferably 2 to 50% by mass, and further preferably 5 to 30% by mass. This is because it is easy to obtain a composition having a storage elastic modulus after curing of 1.0 GPa or less at −20 ° C. and 0.2 to 0.7 GPa at 80 ° C.

The urethane-modified epoxy resin is not particularly limited for its production. For example, it can be produced by reacting urethane and epoxy in a large amount of epoxy (for example, epoxy resin). The epoxy used when producing the urethane-modified epoxy resin is not particularly limited. For example, a conventionally well-known thing is mentioned.
In the present invention, the epoxy equivalent of the urethane-modified epoxy resin and the addition amount thereof indicate the amount as a urethane-modified epoxy resin containing an excessive epoxy resin used in the production.

The rubber particles (B) will be described.
Examples of the rubber particles (B) contained in the composition of the present invention include butadiene rubber, butadiene styrene rubber, butadiene acrylonitrile rubber, acrylic rubber, polyurethane rubber, polyisoprene rubber, fluorine rubber, and silicone rubber. It is not limited to these. Two or more of these can be used in combination.

The rubber particle (B) is preferably a core-shell type particle (B ′) having at least two layers of a core layer and a shell layer (that is, the core-shell type particle (B ′) is a suitable one of the rubber particles (B). Embodiment.).
The core-shell type particles (B ′) preferably have a glass transition temperature of the shell layer of 50 ° C. or higher. The glass transition temperature of the inner layer adjacent to the shell layer is preferably −30 ° C. or lower. This is because a composition having a storage elastic modulus after curing of 1.0 GPa or less at −20 ° C. and 0.2 to 0.7 GPa at 80 ° C. is easily obtained.

  In addition, the core-shell type particles (B ′) are preferably two layers and / or three layers from the viewpoint of superior adhesion performance and flexibility from low temperature to high temperature. From the viewpoint of excellent heat resistance of the cured product, three layers are preferable.

  When the core-shell type particle (B ′) has a two-layer structure, the inner layer adjacent to the shell layer is a core layer. And it is preferable that the glass transition temperature of this core layer is -30 degrees C or less.

  When the core-shell type particle (B ′) has a three-layer structure, the core-shell type particle (B ′) has an intermediate layer as an inner layer adjacent to the shell layer, and the glass transition temperature of the intermediate layer is −30 ° C. or lower. Is preferred. The core-shell type particle (B ′) having a three-layer structure has a core layer having a glass transition temperature of 50 ° C. or more at the center and an intermediate layer having a glass transition temperature of −30 ° C. or less so as to cover the core layer. It is preferable to have a shell layer on the outermost shell having a glass transition temperature of 50 ° C. or higher so as to cover the intermediate layer.

  The core-shell type particle (B ′) may have a structure of four layers or more. For example, a four-layer structure having a layer having a glass transition temperature different from that of the core layer inside the core layer may be employed.

Each layer constituting the core-shell type particle (B ′) will be described.
First, the shell layer will be described.
Although the substance which forms a shell layer is not specifically limited, It is preferable that it is a substance whose glass transition point is 50 degreeC or more, It is more preferable that it is 50-200 degreeC, It is further more preferable that it is 80-200 degreeC. 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 point of the other layer in the core-shell type particle (B ′).

The shell 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.

Moreover, it is preferable that the monomer used when manufacturing a shell layer contains acrylonitrile. Aggregation of core-shell particles can be prevented by the shell layer. Moreover, when the monomer used when manufacturing the shell layer contains highly polar acrylonitrile, the compatibility with the epoxy resin (A) which is a matrix is increased, and the dispersibility is improved.
In addition, when the monomer used in manufacturing the shell layer contains acrylonitrile, the polymer has a nitrile group, so that the nitrile group has a hydrogen bond with a hydroxy group generated by curing of the epoxy resin (A). Can be formed. Further, the nitrile group can act on the interface of the adherend (for example, a steel plate) to enhance the adhesion.
Thus, due to the hydrogen bond with the epoxy resin (A) on which the nitrile group can be formed and / or the action on the adherend, the composition of the present invention has better adhesion performance from low temperature to high temperature and more excellent Can have flexibility.

When the monomer used in manufacturing the shell layer contains acrylonitrile, it contains an aromatic vinyl monomer and a non-aromatic monomer other than acrylonitrile as a monomer copolymerizable with acrylonitrile in addition to acrylonitrile. Can do.
Examples of the aromatic vinyl monomer include styrene, vinyl toluene, α-methyl styrene, monochloro styrene, 3,4-dichlorostyrene, bromostyrene, and the like. Of these, styrene is preferred from the viewpoint of superior adhesion performance and flexibility from low to high temperatures.

  The amount of acrylonitrile is preferably in the range of 70% by mass or less, more preferably in the range of 50% by mass or less, based on the total amount of monomers used for producing the shell layer.

Examples of non-aromatic monomers other than acrylonitrile include alkyl acrylates such as methyl acrylate, ethyl acrylate and butyl acrylate, alkyl methacrylates such as methyl methacrylate and butyl methacrylate; methacrylonitrile and the like. Examples include vinyl cyanide; vinylidene cyanide.
The amount of the non-aromatic monomer other than acrylonitrile is preferably in the range of 70% by mass or less, more preferably in the range of 50% by mass or less, based on the total amount of the monomers used for producing the shell layer. is there.

Moreover, when the monomer used when manufacturing a shell layer contains acrylonitrile, the shell layer may be bridge | crosslinked with the crosslinkable monomer.
Examples of the crosslinkable monomer that can be used in producing the shell layer include divinylbenzene and butylene glycol dimethacrylate. In particular, divinylbenzene is preferable from the viewpoint of excellent adhesion performance and flexibility from low temperature to high temperature. The amount of the crosslinkable monomer is usually in the range of 30% by mass or less, preferably in the range of 0.5 to 20% by mass, based on the total amount of the monomers used for producing the shell layer. Preferably it is the range of 5-15 mass%.

  Moreover, when the monomer used when manufacturing a shell layer contains acrylonitrile, a styrene-acrylonitrile type copolymer and a styrene-acrylonitrile-divinylbenzene type copolymer are preferable for a shell layer. This is because a composition having a storage elastic modulus after curing of 1.0 GPa or less at −20 ° C. and 0.2 to 0.7 GPa at 80 ° C. is easily obtained.

Next, the inner layer adjacent to the shell layer will be described below.
The inner layer adjacent to the shell layer preferably has a glass transition temperature of −30 ° C. or lower, more preferably −110 to −30 ° C., from the viewpoint of superior adhesion performance and flexibility from low temperature to high temperature. More preferably, the temperature is −110 to −40 ° C.

Monomers that can be used in producing the inner layer adjacent to the shell layer can include, for example, alkyl acrylates having 2 to 8 carbon atoms in the alkyl group, and butadiene.
Examples of the acrylic acid alkyl ester having 2 to 8 carbon atoms in the alkyl group include ethyl acrylate, propyl acrylate, butyl acrylate, cyclohexyl acrylate, and 2-ethylhexyl acrylate.
Monomers that can be used in the production of the inner layer adjacent to the shell layer include, for example, acrylic acid alkyl esters or butadienes having an alkyl group with 2 to 8 carbon atoms, and other vinyl-based monomers copolymerizable therewith. A monomer can be used in combination. Examples of other vinyl monomers copolymerizable with acrylic acid alkyl ester include, for example, aromatic vinyl compounds such as styrene, vinyltoluene, and α-methylstyrene, aromatic vinylidene compounds, and cyanogen such as acrylonitrile and methacrylonitrile. And alkyl methacrylates such as vinyl chloride, vinylidene cyanide, methyl methacrylate, and butyl methacrylate.
The amount of an acrylic acid alkyl ester or other vinyl monomer copolymerizable with butadiene is usually in the range of 50% by mass or less based on the total amount of monomers used in producing the inner layer adjacent to the shell layer. Preferably, it is the range of 40 mass% or less.

  The inner layer adjacent to the shell layer may be crosslinked with a crosslinkable monomer. The crosslinkable monomer has the same meaning as described above. The amount of the crosslinkable monomer used is usually in the range of 0.01 to 5% by mass, preferably 0.1%, based on the total amount of monomers that can be used when the inner layer adjacent to the shell layer is produced. It is the range of -2 mass%.

  Monomers that can be used in making the inner layer adjacent to the shell layer can further include a grafting monomer. The grafting monomer is not particularly limited.

The core layer in the case where the core-shell type particle (B ′) has three layers will be described below.
Examples of the monomer that can be used in producing the core layer in the three-layer core-shell type particle (B ′) include aromatic vinyl monomers. The aromatic vinyl monomer has the same meaning as described above.

In addition to the aromatic vinyl monomer, the monomer that can be used for producing the core layer in the three-layer core-shell type particle (B ′) is a non-aromatic monomer or a crosslinkable monomer. Can be included.
Examples of the non-aromatic monomer include alkyl acrylates such as ethyl acrylate and butyl acrylate, alkyl methacrylates such as methyl methacrylate and butyl methacrylate, vinyl cyanide and vinylidene cyanide such as acrylonitrile and methacrylonitrile. The amount of the non-aromatic monomer used is preferably in the range of 50% by mass or less, more preferably in the range of 20% by mass or less, based on the total amount of monomers that can be used when the core layer is produced. .

The core layer in the three-layer core-shell type particle (B ′) may be crosslinked with a crosslinkable monomer.
Examples of the crosslinkable monomer include monomers having two or more polymerizable ethylenically unsaturated bonds in the molecule. Specific examples include, for example, aromatic divinyl monomers such as divinylbenzene, ethylene glycol di (meth) acrylate, butylene glycol di (meth) acrylate, hexanediol (meth) acrylate, oligoethylene glycol di (meth) acrylate, Examples include alkane polyol poly (meth) acrylates such as trimethylolpropane di (meth) acrylate and trimethylolpropane tri (meth) acrylate. Of these, divinylbenzene is particularly preferred.
The amount of the crosslinkable monomer used is usually in the range of 30% by mass or less, preferably in the range of 0.5 to 20% by mass, based on the total amount of monomers that can be used when the core layer is produced. Yes, more preferably in the range of 5 to 15% by mass.

The monomer that can be used in producing the core layer in the three-layer core-shell type particle (B ′) can further contain a grafting monomer.
It is preferable that the glass transition temperature of the core layer in the three-layer core-shell type particles (B ′) is a material having a temperature of 50 ° C. or higher. The glass transition temperature of the core layer 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.

In the composition of the present invention, the rubber particles (B) preferably have an average primary particle diameter of 50 to 500 nm, and more preferably 50 to 300 nm. This is because the rubber particles (B) hardly aggregate and workability is good. Moreover, it is because there exists a tendency for the adhesive strength of the composition of this invention to increase more.
The average primary particle size of the rubber particles (B) means a value obtained by measurement using a zeta potential particle size distribution measuring device (Beckman Coulter).
The rubber particles (B) can be used alone or in combination of two or more.

  The rubber particles (B) are not particularly limited for their production. For example, a conventionally well-known thing is mentioned.

  In the composition of the present invention, the amount of the rubber particles (B) is preferably 5 to 100 parts by mass, more preferably 10 to 100 parts by mass with respect to 100 parts by mass of the epoxy resin (A). . This is because it is easy to obtain a composition having a storage elastic modulus after curing of 1.0 GPa or less at −20 ° C. and 0.2 to 0.7 GPa at 80 ° C. Such a composition is a structural adhesive composition having excellent adhesion performance and flexibility from low temperature to high temperature. If this composition is used for adhesion, it is unlikely to cause interfacial destruction at the time of peeling.

Next, the curing agent (C) will be described.
The hardening | curing agent (C) contained in the composition of this invention 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, polythiol and the like can be used.

  The polythiol is not particularly limited as long as it is a compound having two or more mercapto groups. Examples of thiols having two mercapto groups include alkylene dithiols such as ethanedithiol, propanedithiol, butanedithiol, pentanedithiol, and hexanedithiol; benzenedithiol, toluene-3,4-dithiol, and 3,6-dichloro-1 , 2-benzenedithiol, 1,5-naphthalenedithiol, aromatic dithiols such as 4,4'-thiobisbenzenethiol; dithiols of aromatic hydrocarbon compounds such as benzenedimethanethiol; 2-di- heterocyclic compounds such as n-butylamino-4,6-dimercapto-s-triazine; 2-mercapto-3-thiahexane-1,6-dithiol, 5,5-bis (mercaptomethyl) -3,7-dithianonane -1,9-dithiol, 5- (2-mercap) Ethyl) -3,7 Jichianonan -1,9-thia compounds such as dithiol; dimercaptopropanol, compounds having a hydroxy group such as dithioerythritol, and the like.

Examples of the thiol having three or more mercapto groups include trithioglycerin, 1,3,5-triazine-2,4,6-trithiol (trimercapto-triazine), trimethylolpropane tristhioglycolate, trimethylolpropane. Tristhiopropionate, 1,2,4-tris (mercaptomethyl) benzene, 1,3,5-tris (mercaptomethyl) benzene, 2,4,6-tris (mercaptomethyl) mesitylene, tris (mercaptomethyl) Isocyanurates, tris (3-mercaptopropyl) isocyanurate, trithiols such as 2,4,5-tris (mercaptomethyl) -1,3-dithiolane; pentaerythritol tetrakisthioglycolate, pentaerythritol tetrakisthiopropionate, Examples include tetrathiols such as 1,2,4,5-tetrakis (mercaptomethyl) benzene, tetramercaptobutane, and pentaerythrithiol.
Examples of the polythiol include polythiol (for example, “QE-340M” manufactured by Toray Fine Chemical Co., Ltd.) in which a mercapto group is introduced at the end of a polyether (for example, polyoxypropylene glycol).
You may use a hardening | curing agent (C) in combination of 2 or more types in these.

  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 above epoxy resin (A), rubber particles (B) and curing agent (C), the composition of the present invention may further comprise a catalyst, a curing accelerator, an inorganic filler, organic or A polymer filler, 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 composition having the composition illustrated in the following Table 1 contains an epoxy resin (A), rubber particles (B) and a curing agent (C) as main components, and a storage elastic modulus after curing is 1 at −20 ° C. Since it is 0.0 GPa or less and 0.2 to 0.7 GPa at 80 ° C., it corresponds to the composition of the present invention.
In Table 1, the amounts of the epoxy resin (A), the rubber particles (B), and the curing agent (C) are shown in parts by mass. Moreover, about quantities other than these, it shows by the mass%.

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

The composition of the present invention is a structural adhesive composition having a specific composition in which the storage elastic modulus after curing is 1.0 GPa or less at −20 ° C. and 0.2 to 0.7 GPa at 80 ° C., Adhesive performance and flexibility are excellent not only at low temperatures (about -20 ° C) to normal temperatures but also at high temperatures (about 80 ° C). Therefore, the composition of the present invention is optimal 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 as an adhesive for structural members in the fields of automobiles, vehicles (bullet trains, trains), civil engineering, architecture, electronics, aircraft, and the space industry.

1. Production of Epoxy Resin Composition The components shown in Table 2 were used in the amounts (parts by mass) shown in the same table, and these were uniformly mixed to obtain the composition of the present invention.
2. Evaluation The composition obtained as described above was cured and the storage elastic modulus was measured. First, the composition is kept at 170 ° C. for 30 minutes and cured to produce a sheet, cut into a predetermined size of 10 mm × 30 mm, and then heated at a rate of 5 ° C./min, a measurement frequency of 1 Hz, and a strain of 0.01. Storage modulus at −20 ° C. and 80 ° C. was measured by DMA under the condition of%.
Further, the composition obtained as described above was applied to the surface of a non-plated steel sheet with a thickness of 0.15 mm and subjected to a T-shaped peel strength test. Here, the test was conducted according to JIS K-6850 (1999). The test piece (non-plated steel plate) used was 0.8 mm × 25 mm × 200 mm. The test results are shown in Table 2. Moreover, the fracture | rupture form in the T-shaped peel strength test at 80 degreeC was confirmed. The test results are shown in Table 2.

Details of each component shown in Table 2 are as follows.
Bisphenol A type epoxy resin: Epoxy equivalent 190 g / eq (JER828, manufactured by Japan Epoxy Resin Co., Ltd.)
Bisphenol F type epoxy resin: Epoxy equivalent 185 g / eq (Epicoat 806L, manufactured by Japan Epoxy Resin Co., Ltd.)
Urethane-modified epoxy resin: epoxy equivalent 211 g / eq (EPU-78-11, polyol component: polypropylene glycol (PPG), polyisocyanate component: tolylene diisocyanate (TDI), manufactured by ADEKA)
Rubber modified epoxy resin: Epoxy equivalent 305 g / eq (EPR-1309, NBR modified BisA epoxy resin containing BisA epoxy resin, manufactured by ADEKA)
Three-layer core-shell type particles: Trade name IM-601 (manufactured by Gantz Kasei Co., Ltd., three-layer structure, polymer forming shell layer is acrylonitrile / styrene copolymer, average particle size of primary particles = 200 to 300 nm, shell Glass transition temperature of the layer: about 80 ° C. to 100 ° C., glass transition temperature of the intermediate layer: about −50 ° C. to −60 ° C., glass transition temperature of the core layer: about 80 ° C. to 100 ° C.)
Two-layer core-shell type particles: trade name F-351 (manufactured by Ganz Kasei, average primary particle diameter: 200 to 300 nm, two-layer structure, shell layer components: MMA (methyl methacrylate), shell layer glass transition temperature: (100 ° C to 120 ° C, glass transition temperature of core layer: about -50 ° C to -60 ° C)
Rubber particle-dispersed epoxy resin: Trade name EPR-21 (made by ADEKA, containing bisphenol F type epoxy resin (epoxy equivalent 210 g / eq) and NBR fine particles)
Curing agent (C): Dicyandiamide, trade name Dicy15 (manufactured by Japan Epoxy Resin Co., Ltd.)
Catalyst: 3- (3,4-dichlorophenyl) -1,1-dimethylurea, trade name DUMU99 (manufactured by Hodogaya Chemical Co., Ltd.)
-Filler: Silica (RY-200S, manufactured by Nippon Aerosil Co., Ltd.)

As is apparent from the results shown in Table 2, Comparative Examples 1 and 2 having compositions in which the storage elastic modulus after curing is 1.0 GPa or less at −20 ° C. and does not become 0.2 to 0.7 GPa at 80 ° C. The composition had poor adhesion at high temperatures.
On the other hand, Examples 1 to 5 are compositions having a composition satisfying a storage elastic modulus after curing of 1.0 GPa or less at −20 ° C. and 0.2 to 0.7 GPa at 80 ° C. at a high temperature (80 T-peel strength at (° C.) was good.

  Moreover, about the fracture | rupture form in the T-shaped peeling strength test in 80 degreeC, while Comparative Example 1 and 2 were interface fracture, Examples 1-5 were cohesive fracture. Therefore, the reliability as an adhesive is high.

  It is to be noted that the interface failure occurs at the interface between the adhesive and the steel material that is the adherend, and the cohesive failure occurs within the adhesive layer. 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.

Claims (2)

  It contains an epoxy resin (A), rubber particles (B) and a curing agent (C) as main components, and a storage elastic modulus after curing is 1.0 GPa or less at -20 ° C and 0.2 to 0.7 GPa at 80 ° C. A structural adhesive composition which is a composition to be   The structural adhesive composition according to claim 1, wherein the rubber particles (B) are core-shell type particles (B ').