CN116724098A

CN116724098A - Heat-expandable adhesive composition and heat-expandable adhesive sheet

Info

Publication number: CN116724098A
Application number: CN202280008411.8A
Authority: CN
Inventors: 布施启示
Original assignee: Lintec Corp
Current assignee: Lintec Corp
Priority date: 2021-03-17
Filing date: 2022-03-02
Publication date: 2023-09-08
Also published as: KR20230156301A; TW202244231A; JPWO2022196354A1; WO2022196354A1

Abstract

The present invention relates to a heat-expandable adhesive composition containing a thermosetting resin (A), heat-expandable particles (B) and an inorganic filler (C), wherein the inorganic filler (C) has an average particle diameter (D ₅₀ ) Is 200nm or less.

Description

Heat-expandable adhesive composition and heat-expandable adhesive sheet

Technical Field

The present invention relates to a heat-expandable adhesive composition and a heat-expandable adhesive sheet.

Background

Adhesives have been used in a wide variety of fields of mechanical parts, construction materials, structural materials, and the like. Examples of the form of the adhesive include a liquid adhesive and a sheet-like adhesive, and these adhesives are used in a variety of ways depending on the application.

The liquid adhesive can be used to adhere and fix objects to be adhered having a complicated shape with irregularities by filling a space between the objects to be adhered. However, the liquid adhesive is difficult to control the amount and the portion to be applied, and may cause problems in handling such as dripping and bleeding.

On the other hand, the sheet-like adhesive has excellent handleability and can exhibit excellent connection reliability with respect to adhesion between planes, but has the following limitations: the present invention is not suitable for the application of bonding adherends that cannot be pressurized to each other, and in particular, cannot be used for a method of bonding and fixing the adherends by filling a space created between the adherends.

As an adhesive to be filled into a space, an adhesive having thermal expansibility (hereinafter, also referred to as "thermal expansibility adhesive") has been studied. The thermally expandable adhesive may be used for example for the following purposes: after being placed in the three-dimensional space created between the adherends, the adherends are bonded to each other while filling the three-dimensional space with the adhesive after expansion by heating. As a material that can achieve both the advantage of filling the liquid adhesive into the three-dimensional space and the excellent handleability of the sheet-like adhesive, a thermally expandable adhesive has been studied.

Patent document 1 discloses an adhesive sheet having an expandable adhesive layer containing an epoxy resin containing a polyfunctional epoxy resin, a phenolic resin as a curing agent, an imidazole compound as a curing catalyst, and a temperature-sensitive foaming agent.

Prior art literature

Patent literature

Patent document 1: japanese patent application laid-open No. 2018-21203

Disclosure of Invention

Problems to be solved by the invention

According to the technique of patent document 1, it is considered that an adhesive sheet having characteristics such as quick curability, heat resistance, and adhesiveness in a balanced manner and having excellent properties such as thermal conductivity due to sufficient filling properties can be provided.

However, since the thermally expandable adhesive expands due to foaming of the thermally expandable particles, a large number of voids are contained in the adhesive after expansion. Therefore, the thermal expandable adhesive after expansion has a problem that it is inferior to the liquid adhesive and the sheet-like adhesive in mechanical strength such as elastic modulus and shear strength.

In the case of a liquid adhesive or a sheet-like adhesive, a method of blending an inorganic filler is effective for improving the elastic modulus of a cured product, and in the case of a thermally expandable adhesive, a method of improving the elastic modulus by the same means may be considered. However, the present inventors have found that the mechanical strength after expansion is not sufficiently improved even if a conventional inorganic filler is blended in a heat-expandable adhesive.

The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a thermally expandable adhesive composition having excellent mechanical strength after expansion, and a thermally expandable adhesive sheet using the thermally expandable adhesive composition.

Means for solving the problems

The present inventors have found that the above problems can be solved by adding a specific inorganic filler to a thermally expandable adhesive composition, and have further completed the present invention.

That is, the present invention relates to the following [1] to [12].

[1] A heat-expandable adhesive composition comprising a thermosetting resin (A), heat-expandable particles (B), and an inorganic filler (C),

the average particle diameter (D) of the inorganic filler (C) ₅₀ ) Is 200nm or less.

[2] The heat-expandable adhesive composition according to the above [1], wherein,

the inorganic filler (C) is silica.

[3] The heat-expandable adhesive composition according to the above [2], wherein,

the silica is surface-treated with a silane coupling agent.

[4] The heat-expandable adhesive composition according to any one of the above [1] to [3], wherein,

the content of the inorganic filler (C) is 1 to 50 mass% relative to the total mass (100 mass%) of the active ingredients of the thermally expandable adhesive composition.

[5] The heat-expandable adhesive composition according to any one of the above [1] to [4], wherein,

the maximum expansion temperature of the thermally expandable particles (B) is 50 to 250 ℃.

[6] The heat-expandable adhesive composition according to any one of the above [1] to [5], wherein,

The average particle diameter (D) of the thermally expandable particles (B) ₅₀ ) 1-50 μm.

[7] The heat-expandable adhesive composition according to any one of the above [1] to [6], wherein,

the content of the thermally expandable particles (B) is 10 to 60 mass% relative to the total mass (100 mass%) of the active ingredients of the thermally expandable adhesive composition.

[8] The heat-expandable adhesive composition according to any one of the above [1] to [7], wherein,

the thermosetting resin (A) is an epoxy resin.

[9] The heat-expandable adhesive composition according to any one of the above [1] to [8], further comprising a curing agent (D).

[10] The heat-expandable adhesive composition according to any one of the above [1] to [9], further comprising a curing catalyst (E).

[11] The heat-expandable adhesive composition according to any one of the above [1] to [10], further comprising a thermoplastic resin (F).

[12] A heat-expandable adhesive sheet comprising the heat-expandable adhesive composition according to any one of [1] to [11 ].

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, a thermally expandable adhesive composition having excellent mechanical strength after expansion and a thermally expandable adhesive sheet using the thermally expandable adhesive composition can be provided.

Drawings

Fig. 1 is a schematic cross-sectional view showing one embodiment of the heat-expandable adhesive sheet of the present invention.

Fig. 2 is a schematic cross-sectional view showing another embodiment of the heat-expandable adhesive sheet of the present invention.

Fig. 3 is a schematic cross-sectional view for explaining a method of measuring shear strength.

FIG. 4 is another schematic cross-sectional view for explaining a method of measuring shear strength.

Symbol description

1. Thermally expandable adhesive sheet

2. Release material

3. Substrate material

10. 20 thermally expansive adhesive multilayer sheet

4. 4' aluminum plate

5. 5' spacer

thickness of t spacer

d 1-d 4 distance

Detailed Description

In the present specification, the term "active ingredient" refers to a component other than a diluent solvent among components contained in a composition to be subjected to the formulation.

In the present specification, the weight average molecular weight (Mw) is a value in terms of standard polystyrene measured by Gel Permeation Chromatography (GPC), and specifically, a value measured based on the method described in examples.

In the present specification, "(meth) acrylic" means both "acrylic" and "methacrylic", and other similar terms are also used.

In the present specification, the lower limit value and the upper limit value described in stages may be independently combined with each other with respect to a preferable numerical range (for example, a range of content or the like). For example, according to the description of "preferably 10 to 90, more preferably 30 to 60", the "preferable lower limit value (10)" and the "more preferable upper limit value (60)" may be combined to obtain "10 to 60".

The mechanism of action described in the present specification is only presumed, and does not limit the mechanism that contributes to the effect of the present invention.

[ Heat-expandable adhesive composition ]

The heat-expandable adhesive composition of the present embodiment contains a thermosetting resin (A), heat-expandable particles (B), and an inorganic filler (C), wherein the inorganic filler (C) has an average particle diameter (D ₅₀ ) Is 200nm or less.

In the following description, the expansion and curing of the thermally expandable adhesive composition may be referred to as "expansion curing", and the thermally expandable adhesive composition after expansion curing may be referred to as "expansion cured product".

The thermally expandable adhesive composition of the present embodiment has excellent mechanical strength such as shear strength and elastic modulus of an expanded cured product. The reason for this is not yet determined, but can be presumed as follows.

As described above, the cured product of the heat-expandable adhesive composition tends to have a reduced mechanical strength because it contains a large number of voids therein. Further, even if a general inorganic filler is blended in the heat-expandable adhesive composition, no improvement in mechanical strength is observed in the cured product after sufficient expansion. The reason for this is considered to be that the particle diameter of the inorganic filler is generally the same as or greater than the thickness of the thin partition walls between the voids in the expanded cured product, and therefore, a part is generated in the partition walls between the voids, where the existence rate of the inorganic filler is locally high and the existence rate of the thermosetting resin is remarkably low, and this part is mechanically fragile.

On the other hand, the average particle diameter (D) of the inorganic filler (C) contained in the heat-expandable adhesive composition of the present embodiment ₅₀ ) Since the resin composition is sufficiently small, even in the thin partition wall between the voids, the balance of the presence ratio of the thermosetting resin (a) and the inorganic filler (C) is moderate, and both are densely compounded, whereby the effect of improving the storage modulus by the inorganic filler (C) can be obtained without generating mechanically fragile sites. It is further considered that the mechanical strength of the partition walls constituting the voids is effectively improved due to the high cohesive force between the inorganic fillers (C) having small particle diameters.

The components contained in the thermally expandable adhesive composition will be described in detail below.

< thermosetting resin (A) >)

The heat-expandable adhesive composition of the present embodiment contains a thermosetting resin (a).

That is, the heat-expandable adhesive composition of the present embodiment is a thermosetting adhesive composition, and has a function of bonding the adherends to each other by curing the thermosetting resin (a) after or simultaneously with expansion.

The thermosetting resin (a) is not particularly limited as long as it is a resin curable by heating.

The thermosetting resin (A) may be used alone or in combination of 1 or more than 2.

In the heat-expandable adhesive composition of the present embodiment, from the viewpoint of improving the curability of the thermosetting resin (a), it is preferable that the thermosetting resin (a) be contained and 1 or more selected from the group consisting of a curing agent (D) and a curing catalyst (E) described later be contained.

Examples of the thermosetting resin (a) include: epoxy resin, phenolic resin, melamine resin, urea resin, polyester resin, urethane resin, acrylic resin, polyimide resin, benzoOxazine resins, maleimide resins, and the like. Among them, epoxy resin is preferable.

Examples of the epoxy resin include: glycidyl ether type epoxy resins, glycidyl amine type epoxy resins, glycidyl ester type epoxy resins, and the like. Among them, glycidyl ether type epoxy resins are preferable.

Examples of the glycidyl ether type epoxy resin include: bisphenol-type epoxy resins such as bisphenol-a-type epoxy resins, bisphenol-F-type epoxy resins, and bisphenol-S-type epoxy resins; novolac type epoxy resins such as phenol novolac type epoxy resins and cresol novolac type epoxy resins; an epoxy resin having a dicyclopentadiene skeleton, an epoxy resin having a bisphenol skeleton, an epoxy resin having an aralkyl skeleton, an epoxy resin having a fluorene skeleton, an epoxy resin having a naphthalene skeleton; etc. Among them, bisphenol type epoxy resin and novolak type epoxy resin are preferable, and bisphenol a type epoxy resin and cresol novolak type epoxy resin are more preferable.

The functional group equivalent of the thermosetting resin (A) is not particularly limited, but is preferably 120 to 1500g/eq, more preferably 140 to 1000g/eq, and still more preferably 160 to 500g/eq.

When the functional group equivalent of the thermosetting resin (a) is not less than the above lower limit, a crosslinked structure sufficient to obtain good mechanical strength tends to be easily formed. When the equivalent weight of the functional group of the thermosetting resin (a) is equal to or less than the upper limit, the crosslinking density becomes moderate, and impact resistance and toughness of the expanded and cured product tend to be improved.

The content of the thermosetting resin (a) in the heat-expandable adhesive composition of the present embodiment is not particularly limited, but is preferably 10 to 60 mass%, more preferably 20 to 50 mass%, and even more preferably 25 to 40 mass% with respect to the total mass (100 mass%) of the active ingredients of the heat-expandable adhesive composition.

When the content of the thermosetting resin (a) is not less than the above lower limit, good mechanical strength derived from the thermosetting resin (a) tends to be easily obtained sufficiently. When the content of the thermosetting resin (a) is not more than the upper limit, the effect of adding components other than the thermosetting resin (a) tends to be exhibited sufficiently.

Thermal expansion particle (B)

The thermally expandable particles (B) are particles that expand by the application of heat, and are not particularly limited.

The heat-expandable particles (B) may be used alone or in combination of 1 or more than 2.

The maximum expansion temperature of the thermally expandable particles (B) can be appropriately selected depending on the use of the thermally expandable adhesive composition, and is not particularly limited, but is preferably 50 to 250 ℃, more preferably 80 to 200 ℃, and even more preferably 120 to 180 ℃.

If the maximum expansion temperature of the thermally expandable particles (B) is not less than the above lower limit, unintended expansion of the thermally expandable particles (B) tends to be easily suppressed during production and storage of the thermally expandable adhesive composition. Further, if the maximum expansion temperature of the thermally expandable particles (B) is equal to or lower than the above-mentioned upper limit value, expansion can be achieved by moderate heating, and therefore, there is little limitation on the material of the adherend or the like, and the thermally expandable adhesive composition of the present embodiment tends to be easily used for a wide range of applications.

In the present specification, the maximum expansion temperature of the thermally expandable particles (B) is a value measured by the following method.

(method for measuring maximum expansion temperature of thermally-expansive particles (B))

A sample was prepared by adding 0.5mg of thermally expandable particles (B) to be measured to an aluminum cup having a diameter of 6.0mm (inner diameter: 5.65 mm) and a depth of 4.8mm, and covering the cup with an aluminum cap (diameter: 5.6mm, thickness: 0.1 mm) from above.

The height of the sample was measured using a dynamic viscoelasticity measuring device in a state where a force of 0.01N was applied to the sample from the upper part of the aluminum cap by a indenter. Then, the pressure head was heated from 20 to 300 ℃ at a heating rate of 10 ℃/min with a force of 0.01N applied thereto, and the displacement amount of the pressure head in the vertical direction was measured, and the temperature at which the displacement in the positive direction reached the maximum was regarded as the maximum expansion temperature.

The thermally expandable particles (B) are preferably microencapsulated foaming agents each comprising a shell made of a thermoplastic resin and an encapsulating component encapsulated in the shell, wherein the encapsulating component is gasified when heated to a predetermined temperature.

Examples of the thermoplastic resin constituting the shell of the microencapsulated foaming agent include: polyvinyl alcohol, polyvinyl butyral, polymethyl methacrylate, polyacrylonitrile, polyvinylidene chloride, polysulfone, a copolymer obtained by polymerizing 2 or more monomers forming the structural units contained in these thermoplastic resins, and the like.

Examples of the encapsulating component that is a component encapsulated in the shell of the microencapsulated foaming agent include: propane, propylene, butene, n-butane, isobutane, isopentane, neopentane, n-pentane, n-hexane, isohexane, n-heptane, n-octane, cyclopropane, cyclobutane, petroleum ether, and the like.

These encapsulating components may be used alone in an amount of 1 or in an amount of 2 or more.

The maximum expansion temperature of the thermally expandable particles (B) can be adjusted by appropriately selecting the kind of the encapsulating component.

Average particle diameter (D) of thermally expandable particles (B) ₅₀ ) The particle size is not particularly limited, but is preferably 1 to 50. Mu.m, more preferably 3 to 30. Mu.m, and still more preferably 5 to 15. Mu.m.

Average particle diameter (D) of thermally expandable particles (B) ₅₀ ) When the lower limit is more than the above, the expansion ratio of the heat-expandable adhesive composition tends to be sufficiently increased. Further, the average particle diameter (D) of the thermally expandable particles (B) ₅₀ ) When the amount is equal to or less than the upper limit, the amount of expansion per 1 thermally expandable particle (B) is moderate, and the mechanical strength of the expanded cured product tends to be more excellent.

Average particle diameter (D) of thermally expandable particles (B) ₅₀ ) Mean the average particle diameter (D) before expansion at 23 DEG C ₅₀ ) The measurement can be performed by the method described in examples.

The content of the thermally expandable particles (B) in the thermally expandable adhesive composition of the present embodiment is not particularly limited, but is preferably 10 to 60 mass%, more preferably 20 to 50 mass%, and even more preferably 25 to 40 mass% with respect to the total mass (100 mass%) of the active ingredients of the thermally expandable adhesive composition.

When the content of the thermally expandable particles (B) is not less than the above lower limit, the expansion ratio of the thermally expandable adhesive composition tends to be sufficiently increased. When the content of the thermally expandable particles (B) is equal to or less than the upper limit, the expansion amount of the thermally expandable adhesive composition tends to be moderate, and the mechanical strength of the expanded cured product tends to be more excellent.

Inorganic filler (C) >)

The inorganic filler (C) is not limited as long as the average particle diameter (D ₅₀ ) The wavelength is 200nm or less, and is not particularly limited.

The inorganic filler (C) may be used alone or in combination of 1 or more than 2.

Examples of the inorganic filler (C) include: oxidized metals such as silica, alumina, boehmite, etc.; minerals such as montmorillonite and bentonite; metal, calcium carbonate, magnesium carbonate, calcium sulfate, barium sulfate, aluminum hydroxide, aluminum silicate, calcium silicate, and magnesium silicate; and inorganic particles.

Among them, metal oxide is preferable, and silica is more preferable.

Average particle diameter (D) of inorganic filler (C) ₅₀ ) It is 200nm or less, preferably 1 to 150nm, more preferably 10 to 100nm, still more preferably 30 to 70nm.

Average particle diameter (D) of inorganic filler (C) ₅₀ ) When the upper limit is less than or equal to the above, the inorganic filler (C) is compounded with the thermosetting resin (a) in a well-balanced manner even in the thin partition walls between the voids of the expansion-cured product, and the mechanical strength after the expansion-curing tends to be more excellent. In addition, the average particle diameter (D) of the inorganic filler (C) ₅₀ ) When the lower limit is not less than the above-mentioned lower limit, the occurrence of the sites where the inorganic fillers (C) excessively aggregate with each other can be suppressed, and the decrease in mechanical strength caused by the sites can be suppressed.

Average particle diameter (D) of inorganic filler (C) ₅₀ ) The measurement can be performed by the method described in examples.

Examples of the shape of the inorganic filler (C) include: spherical; non-spherical shapes such as polygonal shapes, plates, flakes, horns, needles, rods, and crushed shapes; etc. Among them, the spherical shape is preferable in view of easy obtaining of good dispersibility and less possibility of occurrence of mechanically fragile portions.

In the present specification, "spherical" means substantially spherical, such as a true sphere or an elliptic sphere. Wherein the particle length and diameter (D _L ) And short diameter (D) _S ) Ratio [ (D) _L )/(D _S )]More than 2 time divisionIs non-spherical. The shape of the inorganic filler (C) is preferably approximately spherical, and the above ratio [ (D) _L )/(D _S )]Preferably 1.5 or less, more preferably 1.3 or less, and still more preferably 1.1 or less.

The shape of the inorganic filler (C) can be confirmed by, for example, a Scanning Electron Microscope (SEM). In addition, for the above ratio [ (D) _L )/(D _S )]For example, the shape of any 50 particles can be observed by using a Scanning Electron Microscope (SEM), and the long diameter (D _L ) And minor diameter (D) _S ) The average value is obtained.

The inorganic filler (C) may be a surface-treated inorganic filler with a coupling agent from the viewpoint of improving affinity with the thermosetting resin (a).

As the coupling agent, a silane coupling agent is preferable.

Examples of the silane coupling agent include silane coupling agents having an epoxy group, an amino group, a (meth) acryloyloxy group, or a vinyl group as a reactive group. Among them, a silane coupling agent having an epoxy group is preferable.

The coupling agent may be used alone or in combination of 1 or more than 2.

The content of the inorganic filler (C) in the heat-expandable adhesive composition of the present embodiment is not particularly limited, but is preferably 1 to 50% by mass, more preferably 2 to 40% by mass, and even more preferably 3 to 30% by mass, based on the total mass (100% by mass) of the active ingredients of the heat-expandable adhesive composition.

When the content of the inorganic filler (C) is not less than the above lower limit, the mechanical strength of the expanded and cured product tends to be sufficiently improved. When the content of the inorganic filler (C) is not more than the upper limit, the occurrence of a portion where the presence ratio of the inorganic filler (C) is too high can be suppressed, and the decrease in mechanical strength caused by the portion tends to be suppressed.

Curing agent (D) >, curing agent (D)

The curing agent (D) is a substance capable of reacting with the thermosetting resin (a) to form a crosslinked structure, and is a component used as needed to improve the curability of the thermosetting resin (a).

The curing agent (D) may be appropriately selected depending on the type of the thermosetting resin (a), and is not particularly limited.

The curing agent (D) may be used alone or in combination of 1 or more than 2.

As the curing agent (D) in the case of using an epoxy resin as the thermosetting resin (a), for example, a compound having 2 or more functional groups capable of reacting with an epoxy group in 1 molecule can be cited.

Examples of the functional group of the curing agent (D) include: and a group obtained by acid anhydride treatment of a phenolic hydroxyl group, an alcoholic hydroxyl group, an amino group, a carboxyl group, and an acid group. Among them, the group obtained by acid anhydride-forming a phenolic hydroxyl group, an amino group and an acid group is preferable, and a phenolic hydroxyl group and an amino group are more preferable.

Among the curing agents (D), as phenolic curing agents having phenolic hydroxyl groups, there may be mentioned, for example: polyfunctional phenol resins, bisphenols, novolak-type phenol resins, dicyclopentadiene-type phenol resins, aralkyl-type phenol resins, and the like.

Among the curing agents (D), amine curing agents having an amino group include dicyandiamide, for example.

Of these, a phenolic curing agent having a phenolic hydroxyl group is preferable, and a novolac type phenolic resin is more preferable. Examples of the novolak type phenol resin include: phenol novolac resins, bisphenol a novolac resins, o-cresol novolac resins, and the like. Among them, o-cresol novolac resin is preferable.

When the heat-expandable adhesive composition of the present embodiment contains the curing agent (D), the content thereof is not particularly limited, but is preferably 20 to 100 parts by mass, more preferably 30 to 80 parts by mass, and still more preferably 40 to 60 parts by mass, relative to the total mass (100 parts by mass) of the thermosetting resin (a).

When the content of the curing agent (D) is not less than the above lower limit, a crosslinked structure sufficient to obtain good mechanical strength tends to be easily formed. When the content of the curing agent (D) is equal to or less than the upper limit, the crosslinking density becomes moderate, and the toughness of the expanded cured product tends to be improved.

Curing catalyst (E) >)

The curing catalyst (E) is a component used as needed to promote curing of the thermosetting resin (a).

The curing catalyst (E) may be used alone or in combination of 1 or more than 2.

Examples of the curing catalyst (E) include: tertiary amines such as triethylenediamine, benzyldimethylamine, triethanolamine, dimethylaminoethanol, and tris (dimethylaminomethyl) phenol; imidazoles (imidazoles in which 1 or more hydrogen atoms are substituted with a group other than a hydrogen atom) such as 2-methylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 2-phenyl-4, 5-dihydroxymethylimidazole, and 2-phenyl-4-methyl-5-hydroxymethylimidazole; organic phosphines such as tributylphosphine, diphenylphosphine, and triphenylphosphine (phosphine obtained by substituting 1 or more hydrogen atoms with an organic group); tetraphenyl groupTetraphenylborates such as tetraphenylborates and triphenylphosphine tetraphenylborates; etc.

Among them, imidazoles are preferable, and 2-phenyl-4, 5-dihydroxymethylimidazole is more preferable.

When the heat-expandable adhesive composition of the present embodiment contains the curing catalyst (E), the content thereof is not particularly limited, but is preferably 0.1 to 1 part by mass, more preferably 0.2 to 0.7 part by mass, and even more preferably 0.3 to 0.5 part by mass, relative to the total mass (100 parts by mass) of the thermosetting resin (a).

When the content of the curing catalyst (E) is not less than the above lower limit, a sufficient curing speed tends to be easily obtained. When the content of the curing catalyst (E) is equal to or less than the upper limit, the curing speed is moderate, and uniformity of the cured product tends to be easily improved.

< thermoplastic resin (F) >)

The heat-expandable adhesive composition of the present embodiment preferably further contains a thermoplastic resin (F).

The thermoplastic resin (F) is a component used as needed to impart film forming property, flexibility, and the like to the heat-expandable adhesive composition.

The thermoplastic resin (F) may be used alone or in combination of 1 or more than 2.

Examples of the thermoplastic resin (F) include: acrylic resins, polyester resins, urethane resins, acrylic urethane resins, silicone resins, rubber resins, phenoxy resins, and the like. Among them, acrylic resins are preferable.

The weight average molecular weight (Mw) of the acrylic resin is not particularly limited, but is preferably 10000 ～ 2000000, more preferably 300000 ～ 1500000, and further preferably 500000 ～ 1000000.

When the weight average molecular weight (Mw) of the acrylic resin is not less than the lower limit, the shape stability tends to be improved when the heat-expandable adhesive composition is formed into a sheet or the like. When the weight average molecular weight (Mw) of the acrylic resin is equal to or less than the upper limit, the shape of the heat-expandable adhesive composition tends to easily follow the uneven surface of the adherend.

The weight average molecular weight (Mw) of the acrylic resin can be measured by the method described in examples.

The monomer constituting the acrylic resin preferably contains a (meth) acrylate.

Examples of the (meth) acrylate constituting the acrylic resin include: methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, sec-butyl (meth) acrylate, tert-butyl (meth) acrylate, pentyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, n-octyl (meth) acrylate, n-nonyl (meth) acrylate, isononyl (meth) acrylate, decyl (meth) acrylate, undecyl (meth) acrylate, dodecyl (meth) acrylate, lauryl (meth) acrylate, tridecyl (meth) acrylate, tetradecyl (meth) acrylate, meat bean Kou Zhi), (pentadecyl (meth) acrylate, hexadecyl (meth) acrylate, palmityl (meth) acrylate, heptadecyl (meth) acrylate, octadecyl (meth) acrylate, and the like are alkyl groups constituting alkyl esters having a chain number of 1 to 18;

Cycloalkyl (meth) acrylates such as isobornyl (meth) acrylate and dicyclopentanyl (meth) acrylate;

aralkyl (meth) acrylates such as benzyl (meth) acrylate;

cycloalkenyl (meth) acrylates such as dicyclopentenyl (meth) acrylate;

cycloalkenyloxyalkyl (meth) acrylates such as dicyclopentenyloxyethyl (meth) acrylate;

imide (meth) acrylates;

glycidyl group-containing (meth) acrylates such as glycidyl (meth) acrylate;

hydroxy group-containing (meth) acrylates such as hydroxymethyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 3-hydroxybutyl (meth) acrylate, and 4-hydroxybutyl (meth) acrylate;

substituted amino group-containing (meth) acrylates such as N-methylaminoethyl (meth) acrylate; etc.

Among them, the monomer constituting the acrylic resin preferably contains an alkyl (meth) acrylate in which the alkyl group constituting the alkyl ester has a chain structure of 1 to 18 carbon atoms, and more preferably contains an alkyl (meth) acrylate in which the alkyl group constituting the alkyl ester has a chain structure of 1 to 4 carbon atoms.

The monomer constituting the acrylic resin further preferably contains a glycidyl group-containing (meth) acrylate in addition to the alkyl (meth) acrylate, and more preferably contains a glycidyl group-containing (meth) acrylate and a hydroxyl group-containing (meth) acrylate in addition to the alkyl (meth) acrylate.

The monomers constituting the acrylic resin may be 1 or 2 or more monomers.

Examples of the monomer other than the (meth) acrylate constituting the acrylic resin include: (meth) acrylic acid, itaconic acid, vinyl acetate, acrylonitrile, styrene, N-methylolacrylamide, and the like.

When the thermoplastic resin (F) is contained in the heat-expandable adhesive composition of the present embodiment, the content thereof is not particularly limited, but is preferably 1 to 20 mass%, more preferably 2 to 15 mass%, and even more preferably 4 to 10 mass% with respect to the total mass (100 mass%) of the active ingredients of the heat-expandable adhesive composition.

When the content of the thermoplastic resin (F) is not less than the above lower limit, the shape of the heat-expandable adhesive composition tends to easily follow the uneven surface of the adherend. When the content of the thermoplastic resin (F) is equal to or less than the upper limit, flexibility is moderate, and the thermoplastic resin (F) can be stored in a roll or sheet shape, and the mechanical strength of the expanded and cured product tends to be further improved.

< other Components >)

The heat-expandable adhesive composition of the present embodiment may contain other components or may not contain other components within a range that does not impair the effects of the present invention.

As the other component, for example, there may be mentioned: resin components other than the above components; additives such as antistatic agents, antioxidants, softeners, rust inhibitors, pigments, dyes, and the like; etc. The other components may be used alone or in combination of at least 2 kinds.

When the heat-expandable adhesive composition of the present embodiment contains the other components, the content of the other components is not particularly limited, but is preferably 0.001 to 5% by mass, more preferably 0.01 to 3% by mass, and even more preferably 0.1 to 1% by mass, relative to the total mass (100% by mass) of the active ingredients of the heat-expandable adhesive composition.

< temperature at 90% of the degree of curing >

The temperature (t 90) at which the heat-expandable adhesive composition of the present embodiment reaches 90% of the curing degree in 1 hour is not particularly limited, but is preferably 100 to 250 ℃, more preferably 120 to 200 ℃, still more preferably 140 to 180 ℃.

When the temperature (t 90) is not less than the lower limit, the storage stability tends to be more excellent. Further, when the temperature (t 90) is equal to or lower than the upper limit, the adhesive composition can be cured by moderate heating, and therefore, the material of the adherend and the like are less limited, and the thermally expandable adhesive composition of the present embodiment tends to be easily used for a wide range of applications.

The curing degree of the heat-expandable adhesive composition can be measured in accordance with JIS K7148-1:2015.

Process for producing heat-expandable adhesive composition

The method for producing the heat-expandable adhesive composition of the present embodiment is not particularly limited, and the composition can be produced by mixing the components by a known method.

The method of mixing the components may be, for example, a method of melt-kneading the components under heating, or a method of mixing the components in a solvent, and then drying the mixture to remove the solvent. Among them, from the viewpoint of suppressing unintended expansion of the thermally expandable particles (B) at the time of mixing, a method of mixing the components in a solvent and then drying is preferable.

Examples of the solvent used for dispersing the components include: aliphatic hydrocarbon solvents such as hexane and heptane; aromatic hydrocarbon solvents such as toluene and xylene; halogenated hydrocarbon solvents such as methylene chloride and vinyl chloride; alcohol solvents such as methanol, ethanol, propanol, and butanol; ketone solvents such as acetone, methyl ethyl ketone, 2-pentanone, isophorone, and cyclohexanone; ester solvents such as ethyl acetate and butyl acetate; cellosolve solvents such as ethyl cellosolve; ether solvents such as propylene glycol monomethyl ether; etc. Among them, aromatic hydrocarbons are preferable, and toluene is more preferable.

From the viewpoint of suppressing expansion of the thermally expandable particles (B) when the solvent is dried, the boiling point of the solvent is preferably a temperature lower than the expansion initiation temperature (t) of the thermally expandable particles (B).

Use of thermally expandable adhesive composition

The application of the heat-expandable adhesive composition of the present embodiment is not particularly limited, and the heat-expandable adhesive composition is suitable for a method of using the heat-expandable adhesive composition in which the space between the adherends is filled with an expanded cured product by expanding and curing the space after filling the space between the adherends.

Examples of the adhesion of the adherend having a three-dimensional space include: in a permanent magnet motor, an electromagnetic steel plate constituting a rotor core is bonded to a permanent magnet, a conductor coil of the motor is bonded to a stator core, and the like. Since these adherends have a three-dimensional space of a complicated shape, the heat-expandable adhesive composition of the present embodiment, which can fill the three-dimensional space and bond the adhesive members together, is suitable.

In addition, the heat-expandable adhesive composition of the present embodiment contains a large number of voids after expansion, and therefore has excellent heat resistance. Therefore, the method is also suitable for filling and bonding materials in various articles such as building materials and vehicle members, which require heat insulation.

The heat-expandable adhesive composition of the present embodiment may be used in a method other than the method for adhering the adherends to each other. Examples of such a method of use include: the thermally expandable adhesive composition of the present embodiment is used as a foaming ink, a construction material itself such as wallpaper, or the like.

[ Heat-expandable adhesive sheet ]

The heat-expandable adhesive sheet according to the present embodiment is formed from the heat-expandable adhesive composition according to the present embodiment.

The heat-expandable adhesive sheet of the present embodiment may have other layers such as a release material and a base material on one or both surfaces thereof. In the following description, when the heat-expandable adhesive sheet has another layer on one or both sides, a multilayer sheet including the heat-expandable adhesive sheet and the other layer is sometimes referred to as a "heat-expandable adhesive multilayer sheet".

Fig. 1 is a schematic cross-sectional view showing one embodiment of the heat-expandable adhesive sheet of the present embodiment. In the embodiment shown in fig. 1, the thermally expandable adhesive sheet 1 is provided with a release material 2 on both sides thereof, and constitutes a thermally expandable adhesive multilayer sheet 10.

Fig. 2 is a schematic cross-sectional view showing another embodiment of the heat-expandable adhesive sheet of the present embodiment. In the embodiment shown in fig. 2, the heat-expandable adhesive sheets 1 are provided on both surfaces of the base material 3, and the release materials 2 are provided on the surfaces of the 2 heat-expandable adhesive sheets 1 opposite to the base material 3, respectively, to constitute a heat-expandable adhesive multilayer sheet 20.

As another embodiment, for example, in the embodiment of fig. 1, an intermediate layer is included between the thermally expandable adhesive sheet 1 and the release material 2. In addition, in the embodiment of fig. 2, an intermediate layer is included at 1 or more portions selected from the group consisting of between the thermally expandable adhesive sheet 1 and the base material 3 and between the thermally expandable adhesive sheet 1 and the release material 2. As the intermediate layer, for example, there may be mentioned: an adhesion assisting layer for enhancing the adhesion strength between the layers, an embedding assisting layer for improving the embedding property of the irregularities to the adherend, a primer layer for improving the adhesion of the adherend at the interface with the adherend after expansion by heating, and the like.

The thickness of the heat-expandable adhesive sheet of the present embodiment is not particularly limited, but is preferably 5 to 1000. Mu.m, more preferably 10 to 100. Mu.m, and still more preferably 20 to 50. Mu.m.

When the thickness of the heat-expandable adhesive sheet is equal to or greater than the lower limit, the film tends to be easily formed into a uniform thickness. When the thickness of the heat-expandable adhesive sheet is equal to or less than the upper limit value, the sheet tends to be easily applied to a narrow three-dimensional space.

< substrate >

The base material that can be used together with the heat-expandable adhesive sheet of the present embodiment can be appropriately selected according to the use of the heat-expandable adhesive sheet.

Examples of the substrate include: resin films, metal foils, papers, nonwoven fabrics, foam materials, and the like.

Examples of the resin constituting the resin film include: polyolefin resins such as polyethylene and polypropylene; vinyl resins such as polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, ethylene-vinyl acetate copolymer and ethylene-vinyl alcohol copolymer; polyester resins such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate; a polystyrene; acrylonitrile-butadiene-styrene copolymer; cellulose triacetate; a polycarbonate; urethane resins such as polyurethane and acrylic modified polyurethane; polymethylpentene; polysulfone; polyether ether ketone; polyether sulfone; polyphenylene sulfide; polyimide resins such as polyether imide and polyimide; polyamide resin; an acrylic resin; a fluorine-based resin; etc.

Examples of the metal constituting the metal foil include: aluminum, tin, chromium, titanium, and the like.

Examples of the paper include: thin layer paper, medium paper, high quality paper, impregnated paper, coated paper, art paper, sulfuric acid paper, glass paper, etc.

Examples of the nonwoven fabric include: a film-like nonwoven fabric is produced from fibers formed of a resin constituting the resin film by a suitable method such as an adhesive method, a needle punching method, a spunbonding method, or a melt blowing method; a Japanese-style nonwoven fabric produced from pulp fibers by a papermaking method, and the like.

Examples of the foaming material include a material obtained by foaming a resin constituting the resin film with a foaming agent or the like.

Among them, a resin film is preferable, and a resin film containing a polyester resin such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate as a constituent material is more preferable.

These substrates may be composed of only 1 layer, or may be a multilayer structure in which 2 or more layers are laminated.

In addition, from the viewpoint of improving interlayer adhesion between the substrate and other layers to be laminated, the surface of the substrate may be subjected to surface treatment by an oxidation method, a concavity and convexity method, an easy-to-adhere treatment, a primer treatment, or the like.

The thickness of the base material is not particularly limited, but is preferably 5 to 500. Mu.m, more preferably 15 to 300. Mu.m, and still more preferably 20 to 200. Mu.m.

When the thickness of the base material is not less than the above lower limit, excellent deformation resistance tends to be easily obtained. When the thickness of the base material is equal to or less than the upper limit, moderate flexibility can be obtained, and handling tends to be easy.

< Release Material >)

Examples of the release material that can be used together with the heat-expandable adhesive sheet of the present embodiment include: a separator subjected to a double-sided peeling treatment, a separator subjected to a single-sided peeling treatment, and the like.

Examples of the release sheet include: a release sheet obtained by coating a release agent on a base material for a release material.

Examples of the base material for the release material include: plastic films, papers, etc.

Examples of the plastic film include: polyester resin films such as polyethylene terephthalate resin, polybutylene terephthalate resin, and polyethylene naphthalate resin; an olefin resin film such as a polypropylene resin and a polyethylene resin; etc.

Examples of the paper include: high quality paper, cellophane, kraft paper, etc.

Examples of the release agent include: rubber-based elastomers such as silicone-based resins, olefin-based resins, isoprene-based resins, and butadiene-based resins; long chain alkyl-based resins, alkyd-based resins, and fluorine-based resins; etc. The stripping agent may be used alone or in combination of 1 or more than 2.

The thickness of the release material is not particularly limited, but is preferably 10 to 200. Mu.m, more preferably 20 to 150. Mu.m, and still more preferably 35 to 80. Mu.m.

When the thickness of the release material is not less than the above lower limit, excellent deformation resistance tends to be easily obtained. When the thickness of the release material is equal to or less than the upper limit, moderate flexibility can be obtained, and handling tends to be easy.

Method for producing heat-expandable adhesive sheet

The method for producing the heat-expandable adhesive sheet according to the present embodiment is not particularly limited, and the heat-expandable adhesive composition according to the present embodiment can be produced by a known method into a sheet.

The sheet of the heat-expandable adhesive composition may be formed by applying the heat-expandable adhesive composition of the present embodiment diluted with a solvent and drying the composition, or may be formed by melt-extruding the heat-expandable adhesive composition. As the solvent in the case of dilution with the solvent, the above-mentioned solvents can be used.

Next, a method of manufacturing the heat-expandable adhesive sheet according to the present embodiment will be described more specifically by taking a method of applying and drying a heat-expandable adhesive composition diluted with a solvent as an example.

In order to form the thermally expandable adhesive multilayer sheet 10 shown in fig. 1, first, the thermally expandable adhesive composition of the present embodiment diluted with a solvent is applied to the release treated surface of the release material 2, and then dried, thereby obtaining a thermally expandable adhesive sheet with release material having the thermally expandable adhesive sheet 1 of the present embodiment formed on one surface of the release material 2. Then, by attaching a separate release material 2 to the exposed surface of the thermally expandable adhesive sheet 1 of the thermally expandable adhesive sheet with release material, a thermally expandable adhesive multilayer sheet 10 can be obtained.

In addition, in the case of forming the thermally expandable adhesive multilayer sheet 20 shown in fig. 2, the thermally expandable adhesive composition of the present embodiment diluted with a solvent is applied to the release treated surface of the release material 2, and then dried, thereby obtaining the thermally expandable adhesive sheet with release material having the thermally expandable adhesive sheet 1 of the present embodiment formed on one surface of the release material 2. Next, by performing the same process, another thermally expandable adhesive sheet with a release material was prepared. Then, 2 thermally expandable adhesive sheets with a release material were respectively adhered to both sides of the base material 3 so that the thermally expandable adhesive sheet 1 became an adhesive face, whereby a thermally expandable adhesive multilayer sheet 20 was obtained.

In the above-described method for producing a thermally expandable adhesive sheet, examples of a method for applying a thermally expandable adhesive composition diluted with a solvent include: spin coating, spray coating, bar coating, blade coating, roll coating, blade coating, die coating, gravure coating, and the like.

In addition, from the viewpoint of suppressing expansion of the thermally expandable particles (B), the step of drying the thermally expandable adhesive composition after application is preferably performed at a temperature lower than the expansion initiation temperature (t) of the thermally expandable particles (B).

Use of thermally expandable adhesive sheet

The use of the heat-expandable adhesive sheet according to the present embodiment is the same as that of the heat-expandable adhesive composition according to the present embodiment described above.

Examples

The present invention will be described more specifically with reference to the following examples, but the present invention is not limited to the following examples. The physical properties in each example were measured by the following method.

[ weight average molecular weight (Mw) ]

The measurement was performed under the following conditions using a gel permeation chromatography apparatus (product name "HLC-8020" manufactured by eastern co., ltd.) and a value measured by conversion from standard polystyrene was used.

(measurement conditions)

Chromatographic column: the composition was obtained by sequentially joining "TSK guard column HXL-L", "TSK gel G2500HXL", "TSK gel G2000HXL", "TSK gel G1000HXL" (both manufactured by Tosoh Co., ltd.)

Column temperature: 40 DEG C

Developing solvent: tetrahydrofuran (THF)

Flow rate: 1.0mL/min

[ thickness of layers ]

The measurement was performed at 23℃using a constant pressure thickness gauge (model: PG-02J, standard: according to JIS K6783, Z1702, Z1709) manufactured by Teclock, inc.

[ average particle diameter (D) of thermally-expansive particles (B) and inorganic filler (C) ₅₀ )]

The particle distribution was measured using a laser diffraction type particle size distribution measuring apparatus (for example, manufactured by Malvern corporation under the product name "Mastersizer 3000").

Then, the particle diameter corresponding to 50% of the cumulative volume frequency calculated from the smaller particle diameter of the particle distribution was taken as the average particle diameter (D ₅₀ )。

[ production of Heat-Expandable adhesive composition and Heat-Expandable adhesive sheet ]

Examples 1 to 3 and comparative examples 1 to 3

The components shown in table 1 were mixed in accordance with the compositions shown in table 1, diluted with methyl ethyl ketone, and stirred, whereby a heat-expandable adhesive composition having an active ingredient concentration of 50 mass% was prepared.

The heat-expandable adhesive composition was applied to a release sheet (product name "SP-PET382150", manufactured by Lindeke Co., ltd.) and a material having a release agent layer formed of a silicone release agent provided on one surface of a polyethylene terephthalate film, and the thickness was 38 μm to form a coating film, and the coating film was dried at 100℃for 60 seconds to form a heat-expandable adhesive sheet having a thickness of 25 μm on the release sheet.

[ measurement of expansion Rate ]

The thermally expandable adhesive sheet with release material prepared in each example was cut into a size of 10mm×10mm, and laminated on the surface of an aluminum plate (thickness 1 mm) having a smooth surface with the thermally expandable adhesive sheet side as an adhesive surface. Then, the material after the release of the release sheet was used as a test sample before the heat treatment. The thickness of the thermally expandable adhesive sheet on the aluminum plate in the test sample before the heat treatment was measured, and the obtained value was used as the thickness T before the heat treatment ₀ 。

Then, the test sample was heated in an oven at 160℃for 1 hour, and then cooled to room temperature (23 ℃) to prepare a heat-treated test sample. Measuring the heat-treated productThe thickness of the thermally expandable adhesive sheet on the aluminum plate in the test sample was set as the thickness T after the heat treatment ₁ 。

T obtained as described above is used ₀ T and T ₁ The expansion ratio was calculated by the following formula.

Expansion ratio (%) =t ₁ ×100/T ₀

[ method for measuring shear Strength ]

The shear strength (hereinafter also referred to as "shear strength 1") in the case of expanding and curing the heat-expandable adhesive sheet while pressing the adherend and the shear strength (hereinafter also referred to as "shear strength 2") in the case of expanding and curing the adherend in the three-dimensional space were measured by the following procedure.

(1) Production of test piece 1 having shear Strength 1

Fig. 3 shows a schematic cross-sectional view for explaining a step of manufacturing the test piece 1 having the shear strength 1.

In the production of the test piece, an aluminum plate 2 sheet (aluminum plate 4 and aluminum plate 4') having a width of 15mm×length of 70mm×thickness of 1mm and having a smooth surface was prepared as an adherend.

The thermally expandable adhesive sheet with release material prepared in each example was cut into a square of 10mm×10mm, and laminated on the surface of the aluminum plate 4 with the thermally expandable adhesive sheet 1 side as an adhesive surface.

Next, the release material was peeled off from the thermally expandable adhesive sheet 1, another aluminum sheet 4' was placed on the exposed surface, the aluminum sheet 4 and the aluminum sheet 4' were made parallel, the aluminum sheets were fixed to each other with a clip, and the thermally expandable adhesive sheet 1 was pressed by the aluminum sheets 4 and 4' on both surfaces.

The bonding position of the heat-expandable adhesive sheet 1 is set so that four sides thereof are the centers of the aluminum plates 4, 4 'in the width direction in the direction parallel to the respective sides of the aluminum plates, and the distance d1 between one end portion of the heat-expandable adhesive sheet 1 and the end portion of the aluminum plate 4 and the distance d2 between the other end portion of the heat-expandable adhesive sheet 1 and the end portion of the aluminum plate 4' are 5mm, respectively.

The sample fixed with the clip was heated in an oven at 160℃for 1 hour, then cooled to room temperature (23 ℃) and the clip was removed to give test piece 1 having a shear strength of 1.

(2) Production of test piece 2 having shear Strength 2

Fig. 4 shows a schematic cross-sectional view for explaining a step of manufacturing the test piece 2 of the shear strength 2.

The thermally expandable adhesive sheet with release material prepared in each example was cut into a square of 10mm×10mm, and the square was laminated on the surface of the aluminum plate 4 with the thermally expandable adhesive sheet 1 side as the adhesive face. The bonding position of the thermally expandable adhesive sheet 1 is the same as that of the test piece 1.

Next, as shown in fig. 4, rectangular parallelepiped spacers 5 and 5' having a thickness t of 50 μm are fixed with an adhesive to the end of the aluminum plate 4 and the position beyond the thermally expandable adhesive sheet 1 from the aluminum plate 4, respectively. At this time, the fixed positions of the spacers 5 and 5 'are set to positions where the distances d3 and d4 between the spacers 5 and 5' and the heat-expandable adhesive sheet 1 are 2mm, respectively.

Next, the release material was peeled off from the thermally expandable adhesive sheet 1, and another aluminum sheet 4' was placed on the spacers 5 and 5', and the aluminum sheet 4' were made parallel, and the aluminum sheets were fixed to each other with a clip, so that the thermally expandable adhesive sheet 1 was placed in the space formed by the aluminum sheets 4 and 4' and the spacers 5 and 5'.

The sample fixed with the clip was heated in an oven at 160℃for 1 hour, then cooled to room temperature (23 ℃) and the clip was removed to give test piece 2 having a shear strength of 2.

(3) Tensile test

The ends of the 2 aluminum plates 4 and 4' of the test piece 1 or 2 after the heat treatment were fixed to chucks of a tensile tester, and the tensile test was performed at room temperature (23 ℃) at 180℃in the tensile direction at a tensile speed of 1 mm/min by using the tensile tester, whereby the shear strength 1 and the shear strength 2 of the thermally expandable adhesive sheet after the expansion curing were measured. In the measurement of the shear strength 1 and the shear strength 2, the failure mode was the cohesive failure of the expanded cured product of the heat-expandable adhesive sheet.

[ method for measuring storage modulus G' at 23 ]

The thermally expandable adhesive sheets with release materials prepared in each example were heated in an oven at 160℃for 1 hour in the state shown in FIG. 1, and then cut into a size of 5mm in width by 15mm in length, and the release materials on both sides were removed to obtain test pieces having a storage modulus G'. The thickness of the test piece was 500. Mu.m, and the thickness of the test piece of comparative example 1 to 3 and the thickness of the test piece of comparative example 2 to 3 were 50. Mu.m. The test piece was subjected to measurement of a storage modulus G 'using a dynamic viscoelasticity measuring device (product name "DMAQ800" manufactured by TA Instruments Co.) under conditions of a test start temperature of 0 ℃, a test end temperature of 200 ℃, a temperature rise rate of 3 ℃ C./min, a vibration frequency of 11Hz, and an amplitude of 5 μm, to obtain a storage modulus G' at 23 ℃.

TABLE 1

Details of the components shown in table 1 are as follows.

[ (A) component ]

Bisphenol a epoxy resin: trade name "jER828", manufactured by mitsubishi chemical Co., ltd., epoxy equivalent 184-194 g/eq

Cresol novolac type epoxy resin: manufactured by Nippon Kagaku Co., ltd., trade name "EOCN-102S", epoxy equivalent 205-225 g/eq

[ (B) component ]

Thermally expandable particles: sorbon fat pharmaceutical Co., ltd., trade name "FN-100SSD", average particle diameter before expansion at a maximum expansion temperature of 120 to 130 ℃ and a maximum expansion temperature of 145 to 155 ℃ and 23℃ (D) ₅₀ )6～11μm

[ (C) component ]

Average particle diameter (D) ₅₀ ) Silica of 50 nm: spherical dioxygen surface-treated with epoxy silane coupling agentSilicon carbide, manufactured by Admatechs, inc., trade name "YA050C-MKK"

Comparative composition

Average particle diameter (D) ₅₀ ) Silica of 0.5 μm: manufactured by Admatechs, inc., trade name "SC2050MA"

[ (D) component ]

O-cresol novolac resin: DIC Co., ltd., trade name "KA-1160", hydroxyl equivalent 117g/eq

[ (E) component ]

Imidazole-based curing catalyst: 2-phenyl-4, 5-dihydroxymethylimidazole, trade name "CUREZOL 2PHZ-PW", manufactured by Sichuanghua chemical industry Co., ltd "

[ (F) component ]

Acrylic resin: acrylic resin formed from Butyl Acrylate (BA)/Methyl Methacrylate (MMA)/Glycidyl Methacrylate (GMA)/2-hydroxyethyl acrylate (HEA) = 55/20/10/15 (mass ratio)

As is clear from table 1, the heat-expandable adhesive compositions of examples 1 to 3, which are the heat-expandable adhesive compositions of the present embodiment, obtained a high storage modulus G' compared with the heat-expandable adhesive composition of comparative example 2 containing no inorganic filler (C), and improved both the shear strength 1 when the adherend was expanded and cured while being pressurized by the adherend, and the shear strength 2 when the adherend was expanded and cured in the three-dimensional space between the adherends.

The heat-expandable adhesive compositions of examples 1 to 3 were blended with a resin composition having an average particle diameter (D ₅₀ ) The thermal expansion adhesive composition of comparative example 3, which was silica of 0.5 μm, had a high storage modulus G' and a high shear strength 2 after expansion curing, and also had a high retention of shear strength. From this, it was found that the particles having the average particle diameter (D ₅₀ ) The inorganic filler (C) having a particle size of 200nm or less exhibits a function of improving mechanical strength particularly remarkably when it is expanded and cured.

Claims

1. A heat-expandable adhesive composition comprising a thermosetting resin (A), heat-expandable particles (B), and an inorganic filler (C),

2. The heat-expandable adhesive composition according to claim 1, wherein,

the inorganic filler (C) is silicon dioxide.

3. The heat-expandable adhesive composition according to claim 2, wherein,

the silicon dioxide is subjected to surface treatment by a silane coupling agent.

4. The heat-expandable adhesive composition according to any one of claim 1 to 3, wherein,

5. The heat-expandable adhesive composition according to any one of claims 1 to 4, wherein,

6. The heat-expandable adhesive composition according to any one of claims 1 to 5, wherein,

7. The heat-expandable adhesive composition according to any one of claims 1 to 6, wherein,

8. The heat-expandable adhesive composition according to any one of claims 1 to 7, wherein,

the thermosetting resin (A) is an epoxy resin.

9. The heat-expandable adhesive composition according to any one of claims 1 to 8, further comprising a curing agent (D).

10. The heat-expandable adhesive composition according to any one of claims 1 to 9, further comprising a curing catalyst (E).

11. The heat-expandable adhesive composition according to any one of claims 1 to 10, further comprising a thermoplastic resin (F).

12. A heat-expandable adhesive sheet formed from the heat-expandable adhesive composition according to any one of claims 1 to 11.