JPH07331186A - Cyanoacrylate adhesive composition - Google Patents

Abstract

PURPOSE:To obtain an easily producible cyanoacrylate adhesive composition excellent in shear bond strength, impact bond strength and storage stability. CONSTITUTION:This composition is one comprising a cyanoacrylate monomer and a core/shell polymer having a core made of a rubber-like polymer and a shell made of a glassy polymer, wherein the cross-linking monomer of the core is presented in an amount of 0.2-4.0wt.% based on the core, and the graft monomer is present in an amount of 0.25-5.0wt.% based on the core.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cyanoacrylate adhesive composition having excellent shear adhesive strength and impact adhesive strength.

[0002]

2. Description of the Related Art A cyanoacrylate adhesive containing an α-cyanoacrylate monomer as an essential component is
Polymerizes and hardens rapidly with a small amount of water adsorbed on the surface of the adherend, and almost all materials except some inactive materials such as polyethylene and Teflon are bonded very firmly in a short time. As a room temperature one-liquid type instant adhesive,
Widely used for bonding metal, plastics, rubber, wood, etc. However, since the cyanoacrylate adhesive is inferior in impact strength, it has been positioned as a temporary fixing adhesive. In order to improve such drawbacks, cyanoacrylate adhesive compositions modified with various additives have been proposed.

US Pat. No. 4,102,945 discloses
Acrylonitrile-butadiene-styrene terpolymer (AB
S), a methacrylate-butadiene-styrene terpolymer (MBS) and a vinylidene chloride-acrylonitrile copolymer (VAC).

In US Pat. No. 4,560,723 (corresponding to Japanese Patent Publication No. 5-59949), the core-shell polymer disclosed in the above US patent has a disadvantage that the storage stability of the cyanoacrylate adhesive is significantly impaired. In addition to the fact that there is a point that there is a point, an adhesive composition comprising a core-shell copolymer as a reinforcing agent that has been treated to remove impurities that cause premature polymerization of cyanoacrylate-based adhesives, and a sustaining agent that prevents heat aging is It is disclosed.
However, this adhesive composition has a problem that although the heat aging of the peeling adhesive strength is suppressed by the addition of a sustaining agent which prevents heat aging, the cohesive force is lowered by the action of the sustaining agent as a plasticizer. Have a point. This decrease in cohesive strength of the adhesive results in deterioration of shear adhesive strength, impact adhesive strength, moisture resistance and the like. Among the sustaining agents disclosed therein, halogenated benzene compounds, in particular, have a peculiar unpleasant odor and are not preferable for the working environment and human body. Further, in order to improve the storage stability of the composition, the removal treatment of impurities in the core-shell polymer is an essential condition, but a multi-step treatment process is not industrially preferable.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a cyanoacrylate adhesive composition which is excellent in shear adhesive strength and impact adhesive strength, can be produced without complicated steps, and is excellent in storage stability. To provide.

[0006]

Means for Solving the Problems As a result of intensive studies to achieve the above object, the present inventors have found that the degree of crosslinking of the core of the core-shell polymer and the degree of chemical bonding (graft ratio) between the core phase and the shell phase. However, they have found that a core-shell polymer within a certain specific range exhibits remarkable effects such as significantly improving the shear adhesive strength and impact adhesive strength of a cyanoacrylate-based adhesive, leading to the present invention.

The cyanoacrylate adhesive composition of the present invention has a cyanoacrylate monomer (a), a rubbery polymer core and a glassy polymer shell, and the crosslinking monomer of the core is 0.2 to 4 with respect to the core. 0.0% by weight, and the core-shell polymer (b) having a graft monomer content of 0.2 to 5.0% by weight based on the core.

The present invention will be described in detail below. The cyanoacrylate monomer which is the first component of the cyanoacrylate adhesive composition of the present invention is a compound represented by the following general formula, which is well known as α-cyanoacrylate.

[0009]

[Chemical 1]

In the formula, R is an ester residue such as an alkyl group, a cycloalkyl group, an alkenyl group, a cycloalkenyl group, an alkynyl group, an aryl group, an alkoxyalkyl group and a trialkylsilylalkyl group. The alkyl group has 1 to 8 carbon atoms such as methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, pentyl, hexyl, heptyl and octyl.
Individual alkyl groups and the like. Preferably, the carbon number is 1
-4 lower alkyl. Examples of the cycloalkyl group include cycloalkyl having 3 to 8 carbon atoms such as cyclopropyl, cyclobutyl, cyclopentyl and cyclohexyl. The alkenyl group is allyl,
Examples thereof include alkenyl groups having 3 to 8 carbon atoms such as isopropenyl, methallyl, 3-butenyl and 3-octenyl.

The cycloalkenyl groups include cyclopropenyl, 1-cyclopentenyl, 2-cyclopentenyl, 3-cyclopentenyl, 1-cyclohexenyl, 2
Examples thereof include cycloalkenyl groups having 3 to 8 carbon atoms such as cyclohexenyl, 3-cyclohexenyl, and 3-cycloheptenyl. The alkynyl group includes propargyl,
Examples thereof include alkynyl having 3 to 8 carbon atoms such as 3-hexynyl and 1-octenyl. Examples of the aryl group include aryl groups having 6 to 8 carbon atoms such as phenyl, tolyl, and xylyl. Examples of the alkoxyalkyl group include C3-8 alkoxyalkyl groups such as methoxyethyl and ethoxyethyl. Examples of the trialkylsilylalkyl group include trimethylsilylethyl, trimethylsilylpropyl and the like.

The second component of the cyanoacrylate adhesive composition of the present invention is a core-shell polymer in which the core is made of a rubbery polymer and the shell is made of a glassy polymer, and a crosslinking monomer is used as a monomer component for forming the core. Is 0.2 to 4.0% by weight, and the grafting monomer is used in the range of 0.2 to 5.0% by weight with respect to the core.

This core-shell polymer can be obtained by a continuous multi-stage emulsion polymerization method in which the polymer of the latter stage is sequentially subjected to seed polymerization in the presence of the polymer of the former stage, so-called multi-stage seed emulsion polymerization method. . Usually, a method of preparing a seed latex by emulsion polymerization, synthesizing a core portion by seed polymerization, and then repeating seed polymerization to obtain a core-shell polymer is used. The production of the core-shell polymer will be described in detail below.

First, the polymerization of the seed particles is carried out by adding all the monomers according to the required characteristics all at once. Methyl methacrylate and ethyl acrylate are preferably used as the monomer.

Polymerization of the core is carried out in the presence of seed latex,
By emulsion-polymerizing the monomers that form a rubber-like polymer,
Polymerization to form a rubber-like polymer having a glass transition temperature of room temperature or lower, preferably −10 ° C. or lower, as a polymer constituting the core. When the glass transition temperature of the core is room temperature or higher, the properties as rubber particles may be lost. Here, the glass transition temperature means a peak value temperature of tan δ in dynamic viscoelasticity measurement.

An alkyl acrylate having an alkyl group having 2 to 8 carbon atoms is preferable as a main component of a monomer forming a rubber-like polymer used in the emulsion polymerization of the core. Examples of the alkyl acrylate having an alkyl group having 2 to 8 carbon atoms include ethyl acrylate, propyl acrylate, butyl acrylate, cyclohexyl acrylate, and 2-ethylhexyl acrylate, and butyl acrylate is particularly preferably used.

In the polymerization of this core, it is particularly preferable to use an alkyl acrylate, but in this case, together with the alkyl acrylate, a monomer copolymerizable therewith, for example, an aromatic vinyl such as styrene, vinyltoluene or α-methylstyrene, It is also possible to copolymerize vinyl cyanide such as aromatic vinylidene, acrylonitrile and methacrylonitrile, vinylidene cyanide, alkyl methacrylate such as methyl methacrylate and butyl methacrylate, or conjugated diene such as butadiene, isoprene and chloroprene.

In the present invention, it is essential to use a crosslinkable monomer and a grafting monomer as a copolymerization monomer in the polymerization of the core.

Examples of the crosslinkable monomer include aromatic divinyl monomers such as divinylbenzene, ethylene glycol diacrylate, ethylene glycol dimethacrylate, butylene glycol diacrylate, hexanediol dimethacrylate, oligoethylene glycol diacrylate, oligoethylene glycol dimethacrylate. , Trimethylol propane diacrylate, trimethylol propane dimethacrylate, trimethylol propane triacrylate, trimethylol propane trimethacrylate and other alkane polyol polyacrylate or alkane polyol polymethacrylate, but especially butylene glycol diacrylate, hexane Diol diacrylate is preferably used.

Such a crosslinkable monomer is contained in an amount of 0.2 to 4.
It can be used in an amount of 0% by weight, preferably 0.5 to 2.0% by weight.

Examples of the grafting agent or grafting monomer include unsaturated carboxylic acid allyl esters such as allyl acrylate, allyl methacrylate, diallyl maleate, diallyl fumarate and diallyl itaconate. It is preferably used.

Such a grafting monomer may be used in an amount of 0.2 to 0.2 of the total amount of monomers used in the polymerization of the core.
It can be used in an amount of 5.0% by weight, preferably 0.5 to 4.0% by weight.

If the cross-linking monomer and the graft monomer deviate from the above ranges, the reproducibility of the effect of improving the adhesive performance may deteriorate.

The core of the rubber-like polymer is preferably in the range of 50 to 90% by weight based on the whole core-shell polymer. When the core content is less than 50% by weight, the effect of improving the adhesive performance may be insufficient.

If the core content exceeds 90% by weight, the shell cannot completely cover the core, and the core-shell polymers are fused with each other to cause agglomeration, resulting in poor reproducibility of the effect of improving the adhesive performance. May be.

In the production of the core-shell polymer, as the polymerization initiator used in the emulsion polymerization of the above-mentioned monomers, persulfate polymerization initiators such as sodium persulfate and potassium persulfate, azobisisobutyronitrile, 2,2 ' -Azobis (2-amidinopropane) dihydrochloride, 2,2'-azobis (2- (2-imidazolin-2-yl) propane, azo-based polymerization initiators such as dimethyl methylpropaneisobutyrate,
Examples thereof include organic peroxide-based initiators such as cumene hydroperoxide and diisopropylbenzene hydroperoxide. Further, as the surfactant used for the polymerization, anionic surfactants such as sodium dodecylbenzenesulfonate and sodium dioctylsulfosuccinate, nonionic surfactants such as polyoxyethylene nonylphenyl ether and polyoxyethylene monostearate. Can be mentioned.

Next, the shell phase composed of the glassy polymer is prepared by preparing the core latex as described above, and then in the presence thereof, the monomer forming the glassy polymer is polymerized to have a glass transition temperature of room temperature or higher, preferably. Can be produced by forming a glassy polymer of 60 ° C. or higher on the outermost shell.

As the monomer forming the glassy polymer, methyl methacrylate or styrene and a monomer copolymerizable therewith are preferably used.

Examples of the monomer copolymerizable with methyl methacrylate include alkyl acrylates such as ethyl acrylate and butyl acrylate, alkyl methacrylates such as ethyl methacrylate and butyl methacrylate, aromatic vinyls such as styrene, vinyltoluene and α-methylstyrene. Examples thereof include vinyl cyanide such as aromatic vinylidene, acrylonitrile and methacrylonitrile, vinyl polymerizable monomers such as vinylidene cyanide, and the like, and particularly preferred are ethyl acrylate, styrene and acrylonitrile. Examples of the monomer copolymerizable with styrene include methyl acrylate,
Alkyl acrylates such as ethyl acrylate, alkyl methacrylates such as methyl methacrylate and ethyl methacrylate, aromatic vinyl such as vinyltoluene and α-methylstyrene, vinyl cyanide such as aromatic vinylidene, acrylonitrile and methacrylonitrile, vinylidene cyanide and the like. Examples thereof include vinyl-polymerizable monomers, but methyl methacrylate and acrylonitrile are particularly preferably used.

Also in the shell polymerization, higher adhesive strength may be obtained by using a small amount of a crosslinking monomer as a copolymerization monomer. In that case, as the crosslinkable monomer, the monomer used in the core polymerization is 4.0% by weight of the total amount of the monomers used in the shell polymerization.
If used in the following range, the effect may be great.

This shell phase is preferably present in the range of 10 to 50% by weight of the total core-shell polymer.
If the outermost shell phase is less than this polymerization range, the shell cannot completely cover the core, and the core-shell polymer will fuse with each other and agglomerate, resulting in poor reproducibility of the effect of improving the adhesive performance. Sometimes.

If the shell phase exceeds 50% by weight,
The effect of improving the adhesive performance of the adhesive obtained by adding the resulting core-shell polymer may be insufficient.

In the core-shell polymer of the present invention,
There may be some polymeric phase, or mesophase, between the core and the final polymeric phase or shell, or between the seed and the core. Such an intermediate phase is, for example, a polymerized monomer having a functional group such as glycidyl methacrylate or unsaturated carboxylic acid, a polymerized monomer forming a glassy polymer such as methyl methacrylate, or butyl acrylate after formation of a seed or a core. It can be formed by appropriately selecting a polymerizing monomer or the like that forms a rubber-like polymer and emulsion-polymerizing it.

The composition of the polymer constituting such an intermediate phase can be variously selected depending on the desired properties of the core-shell polymer.

The polymerization ratio of the intermediate phase can also be appropriately determined depending on the characteristics of the intermediate phase as a polymer, that is, the monomer used. For example, when the glassy polymer is used as the intermediate phase, its polymerization rate may be calculated as a part of the shell, and in the case of a rubbery polymer, it may be calculated as a part of the core.

The structure of the core-shell polymer having such an intermediate phase is such that, for example, when the intermediate phase is polymerized between the core and the shell, another layer, that is, an intermediate layer is present between the core and the shell. Examples of the structure include a multilayer structure, or a structure in which the intermediate phase is dispersed in the core as some granular domains and the core and the intermediate phase are combined to form a so-called salami structure. In the more extreme case of the core-shell polymer having a salami structure, the mesophase to be dispersed may form a new core in the central part of the core. The core-shell polymer having such a structure may occur when a monomer represented by styrene is used as a mesophase-constituting monomer. The shell phase and the intermediate phase are also polymerized using the same polymerization initiator and surfactant as those for the core.

The core-shell polymer used in the present invention exerts a particularly remarkable effect by producing a latex by the above-mentioned seed emulsion polymerization method while satisfying the above-mentioned conditions and then taking it out from the latex by a freeze-thaw method. Will be things.

That is, the latex obtained as described above was
After freezing in an atmosphere of 5 to -40 ° C, 15 to 60 ° C
Thaw, then dehydration treatment, 40 ~ 80
Obtain powder by drying at ℃.

By such a powder take-out operation, most of the solvent and the surfactant used during the emulsion polymerization can be removed.

The particle size of the core-shell polymer thus produced is not particularly limited, but is usually 100 to 100.
0 nm (0.1 to 1 μm), preferably 120 to 750
nm.

The core-shell polymer taken out as described above has the effect of giving a composition excellent in storage stability, even though it has not been subjected to impurity removal treatment. According to the disclosure of the above-mentioned US Pat. No. 4,560,723, it is of course concerned that the ionic impurities remain in the core-shell polymer and the resulting decrease in storage stability of the composition. When the core-shell polymer of the invention is used, the storage stability of the composition is highly maintained.

The cyanoacrylate-based adhesive composition according to the present invention is based on 100 parts by weight of cyanoacrylate.
It is obtained by adding 3 to 30 parts by weight, preferably 5 to 20 parts by weight, of the above core-shell polymer.
When the amount of this core-shell polymer is less than 3 parts by weight, the effect of improving the adhesive performance of the obtained cured adhesive composition may not be observed, and when it is more than 30 parts by weight, the cured product of the obtained adhesive composition. May have significantly impaired rigidity and heat resistance.

The cyanoacrylate adhesive composition according to the present invention can be easily prepared by adding a predetermined amount of the core-shell polymer to cyanoacrylate and stirring the mixture at a temperature of 40 to 60 ° C. for several hours.

Further, the adhesive composition according to the present invention includes a thickener, a filler, a filler, a crosslinking agent, an anionic polymerization inhibitor,
It is also possible to add an appropriate amount of a known additive for cyanoacrylate adhesives such as a radical polymerization inhibitor, an adhesion improver, a heat resistance improver, a water resistance improver, a curing accelerator and a coloring agent.

[0045]

EFFECTS OF THE INVENTION The cyanoacrylate adhesive composition of the present invention has an excellent effect on shear adhesive strength and impact adhesive strength, and can be used as a household or industrial instant adhesive.

[0046]

The present invention will be described below with reference to examples and comparative examples, but the present invention is not limited to these examples.

The "parts" in the examples and comparative examples and the numerical values in the tables represent parts by weight. Abbreviations used in Examples and Comparative Examples are as follows. * Cyanoacrylate methyl α-cyanoacrylate MCA ethyl α-cyanoacrylate ECA allyl α-cyanoacrylate ACA ethoxyethyl α-cyanoacrylate EECA * sustaining agent diphenylmethane DPM * monomer butadiene Bd 2-ethylhexyl acrylate 2EHA n-butyl acrylate BA methyl methacrylate MMA Ethyl acrylate EA Acrylonitrile AN Styrene St Allyl methacrylate AlMA 1,4-butylene glycol diacrylate BGA Divinylbenzene DVB * Surfactant Daiichi Kogyo Seiyaku (manufactured) Neocor P NP (sodium dioctyl sulfosuccinate) Kao (manufactured) Perex SSL SSL (sodium alkyl diphenyl ether disulfonate) * Others On-water DIW Sodium hydrogen carbonate SBC Sodium persulfate SPS

[Test Method] * Measurement of Weight Average Particle Diameter The weight average particle diameter of the core-shell polymer was measured by LPA-3000 manufactured by Otsuka Electronics Co., Ltd.

* Shear Adhesive Strength The tensile shear adhesive strength was measured according to JIS K 6861. The test piece is degreased 100 × 25 × 1.6m
m of cold-rolled steel plate (SPCC-SD), the welded part (10 × 25 mm) was sanded with # 240 sandpaper and then washed, and the adhesive was applied to the adhered part. , 24 ± 1 ° C., 55 ± 5 RH% for 24 hours for adhesion. The shear bond strength was Tensilon, and the maximum load at break was measured at a tensile speed of 10 mm / min.

* Impact bond strength The impact bond strength was measured according to JIS K 6855. 40x25x20mm and 25x12.5x10mm
Of the two types of iron test pieces, the adhesive surfaces of the test piece-1 and the test piece-2, respectively, are sanded with # 240 sandpaper and then washed to remove the adhesive surface of the test piece-2 (25 × 12.5 mm). )
After applying the adhesive to the test piece-1, the test piece-2 was fixed with a weight of about 170 g and left in an environment of 24 ± 1 ° C. and 55 ± 5 RH% for 24 hours for adhesion. Impact bond strength is
It was measured with an impact tester manufactured by Toyo Seiki Co., Ltd.

Example 1 Production of Core-Shell Polymer A and Preparation of Cyanoacrylate Adhesive Composition DIW 427.5 g with 10 L reflux condenser, 1% N
10.8 g of P aqueous solution and 72.5 g of 1% SBC aqueous solution were charged, and the temperature was raised to 70 ° C. while stirring under a nitrogen stream. E
After adding 36.0 g of A and dispersing for 10 minutes,
A 2% SPS aqueous solution (18.0 g) was added and the reaction was carried out with stirring for 1 hour. Finally, it was diluted with 1980 g of DIW to obtain a seed latex.

Subsequently, at 70 ° C., 300.0 g of a 2% SPS aqueous solution was added, and the following monomer emulsion 4314.
After continuously feeding 0 g over 240 minutes, the temperature was raised to 90 ° C. and an aging reaction was performed for 1 hour to obtain a core latex.

First-stage monomer emulsion BA 2889.9 g BGA 14.8 g AlMA 59.3 g 1% NP 1050.0 g 1% SBC 150.0 g DIW 150.0 g

Next, the shell was polymerized by cooling to 70 ° C. 100.0 g of a 2% SPS aqueous solution was added, 1800.0 g of the following monomer emulsion was continuously fed over 180 minutes, and then the temperature was raised to 90 ° C. to carry out an aging reaction for 1 hour.

Second-stage monomer emulsion MMA 995.0 g BGA 5.0 g 1% NP 400.0 g 1% SBC 100.0 g DIW 300.0 g

After completion of aging, the mixture was cooled to 30 ° C. and filtered through a 300-mesh stainless wire net to give a weight average particle size of 542.
nm core-shell polymer latex was obtained.

This latex was once frozen at −30 ° C., thawed, dehydrated and washed in a centrifuge, and then air-dried at 60 ° C. for 24 hours to obtain a core-shell polymer A.

The cyanoacrylate adhesive composition was prepared as follows. EC in a 500 ml beaker
300 g of A was weighed and the stirring blade was rotated at 300 rPm by a three-one motor. After 30 g of the core-shell polymer A was added thereto, the temperature was adjusted to 50 ° C. with a heater and the mixture was stirred for 4 hours. After that, the heater was stopped and the mixture was allowed to cool to room temperature and further stirred for 4 hours to obtain a cyanoacrylate-based adhesive composition.

Examples 2 and 3: Preparation of core shell polymer A cyanoacrylate adhesive composition The same operation as in Example 1 was carried out with the composition shown in Table 2,
A cyanoacrylate-based adhesive composition was obtained.

Examples 4-6: Core Shell Polymer B,
Production of C and D and Preparation of Cyanoacrylate Adhesive Composition The same procedure as in Example 1 was carried out with the monomer composition shown in Table 1 to obtain core-shell polymers B, C and D. Then Table 2
The same operation as in Example 1 was carried out with the composition shown in to obtain a cyanoacrylate-based adhesive composition.

Examples 7 to 9: Preparation of cyanoacrylate adhesive composition of core-shell polymer A In the composition shown in Table 2, MCA and A were used instead of ECA.
Perform the same operation as in Example 1 using CA and EECA,
A cyanoacrylate-based adhesive composition was obtained.

Comparative Examples 1 to 4: Adhesive strength of various cyanoacrylates Blank ECA, MCA, ACA and EECA
The shear bond strength and impact bond strength of each were measured.

Comparative Example 5 Production of Core-Shell Polymer E and Preparation of Cyanoacrylate Adhesive Composition A core-shell polymer E was obtained by the same procedure as in Example 1 with the monomer composition shown in Table 1. Then, the same operation as in Example 1 was carried out with the composition shown in Table 2 to obtain a cyanoacrylate-based adhesive composition.

Comparative Examples 6 and 7: Core-shell polymer KM3
30, Dispersion of BTA751 in ECA KM330 (produced by Rohm & Haas Co., acrylic core shell polymer) and BTA751 (produced by Kureha Chemical Industry Co., Ltd., MBS core shell polymer) were each formulated in the composition shown in Table 2. The same operation as in 1 was performed. Within 30 minutes after adding each core-shell polymer and adjusting the temperature, the temperature of the solution rapidly increased and the ECA gelled.

Comparative Example 8 Preparation of Cyanoacrylate Adhesive Composition of Sustainer DPM In the compounding composition shown in Table 2, DPM which is a sustainer was added to ECA.
Was added to and dissolved at room temperature with stirring.

Comparative Example 9 Preparation of Cyanoacrylate Adhesive Composition of Core-shell Polymer C and Sustainer DPM In the compounding composition shown in Table 2, DPM which is a sustainer was added to ECA.
Was added to and dissolved at room temperature with stirring. Then Table 2
EC with a predetermined amount of core-shell polymer C in the composition shown in
Then, the same operation as in Example 1 was performed to obtain a cyanoacrylate-based adhesive composition.

[0067]

[Table 1]

[0068]

[Table 2]

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Junji Oshima 3-10-8 Uenohigashi, Toyonaka City, Osaka Prefecture

Claims (8)

[Claims] 1. A cyanoacrylate monomer (a), a rubber-like polymer core and a glass-like polymer shell are included, and the crosslinking monomer of the core is 0.2 to 4.0 with respect to the core.
% By weight, graft monomer 0.2 to 5.
A cyanoacrylate-based adhesive composition containing the core-shell polymer (b) in an amount of 0% by weight. 2. The adhesive composition according to claim 1, wherein the core-shell polymer is separated by a freeze-thaw method in the step of taking out from the latex. 3. The adhesive composition according to claim 1, wherein the core-shell polymer is present in an amount of 3 to 30 parts by weight based on 100 parts by weight of the cyanoacrylate monomer. 4. The adhesive composition according to claim 1, wherein the core of the core-shell polymer has a glass transition temperature of room temperature or lower and the shell has a glass transition temperature of room temperature or higher. 5. The adhesive composition according to claim 1, wherein the core of the core-shell polymer is an acrylic rubber. 6. The adhesive composition according to claim 1, wherein the constituent monomer of the acrylic rubber is an alkyl acrylate having an alkyl having 2 to 8 carbon atoms. 7. The adhesive composition according to claim 1, wherein the graft monomer is an unsaturated carboxylic acid allyl ester. 8. The adhesive composition according to claim 1, wherein the shell of the core-shell polymer contains 4.0% by weight or less of a crosslinking monomer.