High frequency dielectric heating adhesive, structure, and method for manufacturing the structure

Abstract

This adhesive for high-frequency dielectric heating contains a thermoplastic resin (A), the thermoplastic resin (A) contains a styrene-base copolymer resin (a1), the content of the styrene-base copolymer resin (a1) in the thermoplastic resin (A) is 40-100 vol%, the content of the styrene-base monomer units in the styrene-base copolymer resin (a1) is 10-90 mass%, the tensile modulus of the adhesive for high-frequency dielectric heating is greater than or equal to 20 MPa, and the dielectric property (tan δ / ε'r) of the adhesive for high-frequency dielectric heating is greater than or equal to 0.005. (tan δ is the dielectric tangent at 23°C and a frequency of 40.68 MHz, and ε'r is the relative permittivity at 23°C and a frequency of 40.68 MHz.)

Description

[Technical Field]

[0001] The present invention relates to an adhesive for high-frequency dielectric heating, a structure, and a method for manufacturing a structure. [Background technology]

[0002] As a method for joining a plurality of adherends to produce a laminate, for example, a method has been proposed in which an adhesive is interposed between the adherends and a dielectric heating treatment, an induction heating treatment, an ultrasonic welding treatment, a laser welding treatment, or the like is performed.

[0003] For example, Patent Document 1 discloses a method of thermally bonding a surface sheet having a resin blend of a polyolefin resin and a styrene copolymer resin and a film layer containing silica. The film layer described in Patent Document 1 contains a resin blend containing 50 parts by mass of a styrene copolymer resin and 5 parts by mass of silica per 100 parts by mass of polyolefin resin. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-148839 Summary of the Invention [Problem to be solved by the invention]

[0005] The topsheet disclosed in Patent Document 1 has a low content of styrene copolymer resin in the resin blend contained in the film layer. For this reason, for example, when the topsheet disclosed in Patent Document 1 is bonded to an adherend containing a styrene resin, it is difficult to bond the topsheet and the adherend in a short period of time, and the adhesion of the topsheet to the adherend is insufficient.

[0006] Furthermore, conventional adhesives containing styrene-based resins have room for further improvement in strength properties such as fracture toughness.

[0007] The object of the present invention is to provide a high-frequency dielectric heating adhesive containing a styrene-based resin that can be bonded in a short time and has improved fracture toughness, as well as a structure in which adherends are bonded with the high-frequency dielectric heating adhesive and a method for manufacturing the structure. [Means for solving the problem]

[0008] According to one aspect of the present invention, there is provided a high-frequency dielectric heating adhesive, the high-frequency dielectric heating adhesive comprising a thermoplastic resin (A), the thermoplastic resin (A) comprising a styrene-based copolymer resin (a1), the content of the styrene-based copolymer resin (a1) in the thermoplastic resin (A) being 40% by volume or more and 100% by volume or less, the content of styrene-based monomer units in the styrene-based copolymer resin (a1) being 10% by mass or more and 90% by mass or less, the high-frequency dielectric heating adhesive having a tensile modulus of elasticity of 20 MPa or more, and a dielectric characteristic (tanδ / ε'r) of 0.005 or more. (tanδ is the dielectric tangent at 23°C and a frequency of 40.68MHz, ε'r is the relative permittivity at 23°C and a frequency of 40.68 MHz.)

[0009] In the high-frequency dielectric heating adhesive according to one aspect of the present invention, the high-frequency dielectric heating adhesive preferably further contains a dielectric filler (B) that generates heat when a high-frequency electric field is applied thereto.

[0010] In the adhesive for high-frequency dielectric heating according to one aspect of the present invention, the dielectric filler (B) is preferably at least one selected from the group consisting of zinc oxide, silicon carbide, titanium oxide, and barium titanate.

[0011] In the high-frequency dielectric heating adhesive according to one aspect of the present invention, the flow starting temperature of the high-frequency dielectric heating adhesive is preferably 80°C or higher and 250°C or lower.

[0012] In the adhesive for high-frequency dielectric heating according to one aspect of the present invention, the styrene copolymer resin (a1) is preferably a styrene elastomer.

[0013] In the adhesive for high-frequency dielectric heating according to one aspect of the present invention, the styrene copolymer resin (a1) is preferably a hydrogenated resin.

[0014] In the adhesive for high-frequency dielectric heating according to one aspect of the present invention, the thermoplastic resin (A) preferably further contains a thermoplastic resin (a2) different from the styrene copolymer resin (a1).

[0015] In the high-frequency dielectric heating adhesive according to one aspect of the present invention, the content of the styrene copolymer resin (a1) is preferably 20% by volume or more and 98% by volume or less, based on the total volume of the high-frequency dielectric heating adhesive.

[0016] In the high-frequency dielectric heating adhesive according to one aspect of the present invention, the high-frequency dielectric heating adhesive is preferably used by applying a high-frequency electric field of 3 MHz or more and 300 MHz or less.

[0017] In one embodiment of the high-frequency dielectric heating adhesive of the present invention, the high-frequency dielectric heating adhesive is an adhesive for joining one or more adherends, and it is preferable that at least one of the one or more adherends contains a resin having an aromatic ring.

[0018] In the high-frequency dielectric heating adhesive according to one aspect of the present invention, the resin having an aromatic ring is preferably a styrene-based resin.

[0019] In the high-frequency dielectric heating adhesive according to one aspect of the present invention, the high-frequency dielectric heating adhesive is preferably an adhesive sheet.

[0020] In the high-frequency dielectric heating adhesive according to one aspect of the present invention, the adhesive sheet preferably has a thickness of 5 μm or more and 2000 μm or less.

[0021] According to one aspect of the present invention, there is provided a structure in which one or more adherends are bonded with the high-frequency dielectric heating adhesive according to the above-described aspect of the present invention.

[0022] According to one aspect of the present invention, there is provided a method for manufacturing a structure, comprising the steps of placing a high-frequency dielectric heating adhesive according to one aspect of the present invention described above on one or more adherends, and applying a high-frequency electric field of 3 MHz or more and 300 MHz or less to the high-frequency dielectric heating adhesive to join the adherends.

[0023] According to one aspect of the present invention, it is possible to provide a high-frequency dielectric heating adhesive containing a styrene-based resin that can be bonded in a short time and has improved fracture toughness, as well as a structure in which an adherend is bonded with the high-frequency dielectric heating adhesive and a method for manufacturing the structure. [Brief explanation of the drawings]

[0024] [Figure 1A] 1 is a schematic cross-sectional view showing an example of a high-frequency dielectric heating adhesive according to an embodiment of the present invention. [Figure 1B] FIG. 2 is a schematic cross-sectional view showing another example of a high-frequency dielectric heating adhesive according to the present embodiment. [Figure 1C] FIG. 2 is a schematic cross-sectional view showing another example of a high-frequency dielectric heating adhesive according to the present embodiment. [Figure 2] FIG. 1 is a schematic cross-sectional view illustrating an example of a structure according to an embodiment of the present invention. [Figure 3] FIG. 10 is a schematic cross-sectional view illustrating another example of the structure according to the present embodiment. [Figure 4] 1 is a schematic diagram illustrating an example of high-frequency dielectric heating treatment using a high-frequency dielectric heating adhesive and a dielectric heating device according to the present embodiment. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0025] [High frequency dielectric heating adhesive] The high-frequency dielectric heating adhesive according to this embodiment contains a thermoplastic resin (A). The thermoplastic resin (A) contains a styrene copolymer resin (a1). The content of the styrene copolymer resin (a1) in the thermoplastic resin (A) is 40% by volume or more and 100% by volume or less. The content of styrene monomer units in the styrene copolymer resin (a1) is 10% by mass or more and 90% by mass or less. The high-frequency dielectric heating adhesive according to this embodiment has a tensile modulus of elasticity of 20 MPa or more. The high-frequency dielectric heating adhesive according to this embodiment also has a dielectric characteristic (tanδ / ε'r) of 0.005 or more. (tanδ is the dielectric tangent at 23°C and a frequency of 40.68MHz, ε'r is the relative permittivity at 23°C and a frequency of 40.68 MHz.)

[0026] <Thermoplastic resin (A)> The thermoplastic resin (A) contains a styrene copolymer resin (a1). The thermoplastic resin (A) may contain a thermoplastic resin (a2) different from the styrene copolymer resin (a1), or may not contain a thermoplastic resin (a2). The thermoplastic resin (a2) will be described later.

[0027] (Styrene-based copolymer resin (a1)) In the adhesive for high frequency dielectric heating according to this embodiment, the content of the styrene copolymer resin (a1) relative to the entire thermoplastic resin (A) is 40% by volume or more and 100% by volume or less on a volume basis. If the content of the styrene copolymer resin (a1) relative to the total thermoplastic resin (A) is 40% by volume or more, for example, when the high-frequency dielectric heating adhesive is joined to an adherend containing a resin having an aromatic ring, the adhesion between the adherend and the high-frequency dielectric heating adhesive of this embodiment is likely to be improved.

[0028] The content of the styrene copolymer resin (a1) in the thermoplastic resin (A) is, on a volume basis, preferably 45% by volume or more, more preferably 50% by volume or more, even more preferably 55% by volume or more, and even more preferably 60% by volume or more. The upper limit of the content of the styrene copolymer resin (a1) in the thermoplastic resin (A) is not particularly limited, and may be, for example, less than 100% by volume, 95% by volume or less, 92% by volume or less, or 90% by volume or less, on a volume basis. If the content of the styrene copolymer resin (a1) in the thermoplastic resin (A) is 45% by volume or more, the adhesiveness to the adherend is likely to be higher when the thermoplastic resin (A) is bonded to an adherend containing a resin having an aromatic ring, for example.

[0029] The content of the styrene copolymer resin (a1) is, on a volume basis, preferably 20% by volume or more, more preferably 30% by volume or more, even more preferably 40% by volume or more, and even more preferably 50% by volume or more, based on the total volume of the high-frequency dielectric heating adhesive. The content of the styrene copolymer resin (a1) is preferably 98% by volume or less, and more preferably 95% by volume or less, based on the volume of the entire high-frequency dielectric heating adhesive. If the content of the styrene copolymer resin (a1) in the entire high-frequency dielectric heating adhesive is 20% by volume or more, the adhesive strength to the adherend is likely to be higher when the adhesive is bonded to an adherend containing, for example, a resin having an aromatic ring. If the content of the styrene copolymer resin (a1) in the entire high-frequency dielectric heating adhesive is 98% by volume or less, the dielectric properties of the high-frequency dielectric heating adhesive can be easily improved, and the adhesive strength to the adherend can be easily improved.

[0030] In the adhesive for high-frequency dielectric heating according to this embodiment, the amount of styrene-based monomer units contained in the styrene-based copolymer resin (a1) is 10 mass % or more and 90 mass % or less on a mass basis. If the content of styrene-based monomer units in the styrene-based copolymer resin (a1) is 10 mass% or more, it is easy to improve the adhesion of the high-frequency dielectric heating adhesive to an adherend containing a resin having an aromatic ring, and it is also easy to improve the heat resistance in an assumed actual use environment. If the content of styrene-based monomer units in the styrene-based copolymer resin (a1) is 90 mass% or less, the fracture toughness of the high-frequency dielectric heating adhesive is likely to be improved, and therefore, for example, when the high-frequency dielectric heating adhesive according to this embodiment is used to join adherends and an impact is applied to the structure, it becomes easier to prevent the structure from being destroyed.

[0031] The content of styrene-based monomer units in the styrene-based copolymer resin (a1) is, on a mass basis, preferably 15 mass% or more, more preferably 20 mass% or more, even more preferably 25 mass% or more, even more preferably 30 mass% or more, even more preferably 40 mass% or more, and even more preferably 50 mass% or more. The content of styrene-based monomer units in the styrene-based copolymer resin (a1) is preferably 80% by mass or less, more preferably 70% by mass or less, based on mass. If the content of styrene-based monomer units in the styrene-based copolymer resin (a1) is 15% by mass or more, when the resin is bonded to an adherend containing a resin having an aromatic ring, the adhesiveness to the adherend is likely to be higher. If the content of styrene-based monomer units in the styrene-based copolymer resin (a1) is 80 mass % or less, the fracture toughness of the adhesive for high-frequency dielectric heating tends to be higher.

[0032] In this specification, the term "styrene copolymer resin" refers to a resin obtained by copolymerizing a styrene monomer with another monomer. That is, the styrene copolymer resin contains a styrene monomer unit and another monomer unit different from the styrene monomer unit. The styrene monomer refers to a monomer having a styrene skeleton. In addition, in this specification, a styrene-based resin is a resin having a styrene skeleton, and represents at least one of a styrene-based homopolymer resin (a homopolymer containing a styrene-based monomer unit) and a styrene-based copolymer resin (a copolymer containing a styrene-based monomer unit).

[0033] Examples of the styrene copolymer resin (a1) include resins obtained by copolymerizing a styrene monomer such as α-methylstyrene or β-methylstyrene with an aliphatic monomer (a monomer having an aliphatic compound skeleton). The styrene copolymer resin may be a hydrogenated styrene resin (hydrogenated resin) obtained by hydrogenating a copolymer resin of a styrene monomer and an aliphatic monomer.

[0034] The styrene copolymer resin (a1) is preferably a styrene elastomer. In this specification, the styrene copolymer resin (a1) includes a styrene elastomer.

[0035] If the styrene copolymer resin (a1) is a styrene elastomer, the fracture toughness of the high-frequency dielectric heating adhesive is more likely to be improved. Examples of styrene elastomers include styrene-conjugated diene copolymers and styrene-olefin copolymers. Specific examples of styrene-conjugated diene copolymers include unhydrogenated styrene-conjugated diene copolymers such as styrene-butadiene copolymer, styrene-butadiene-styrene copolymer (SBS), styrene-butadiene / butylene-styrene copolymer, styrene-isoprene copolymer, styrene-isoprene-styrene copolymer (SIS), and styrene-ethylene / isoprene-styrene copolymer; and hydrogenated styrene-conjugated diene copolymers such as styrene-ethylene / propylene-styrene copolymer (SEPS) and styrene-ethylene / butylene-styrene copolymer (SEBS). The styrene elastomer may be hydrogenated (hydrogenated resin) or unhydrogenated.

[0036] The styrene copolymer resin (a1) is preferably a hydrogenated resin, and more preferably a hydrogenated resin of a styrene elastomer. If the styrene copolymer resin (a1) is a hydrogenated resin, reduction due to ozone degradation is less likely to occur, and the weather resistance of the high-frequency dielectric heating adhesive is more likely to be improved. By improving weather resistance, for example, the decrease in fracture toughness over time is suppressed.

[0037] The styrene copolymer resin (a1) may be used alone or in combination of two or more. For example, it may be at least one selected from the group consisting of styrene-butadiene-styrene copolymer (SBS), styrene-isoprene-styrene copolymer (SIS), and styrene-ethylene / butylene-styrene copolymer (SEBS). Among these, the styrene copolymer resin (a1) preferably contains styrene-ethylene / butylene-styrene copolymer (SEBS).

[0038] (thermoplastic resin (a2)) The thermoplastic resin (a2) is a component that may be contained in the thermoplastic resin (A) as needed. The content of the thermoplastic resin (a2) in the thermoplastic resin (A) is, on a volume basis, 0% by volume or more and 60% by volume or less.

[0039] When the thermoplastic resin (A) contains the thermoplastic resin (a2), the content of the thermoplastic resin (a2) in the thermoplastic resin (A) is, on a volume basis, preferably more than 0% by volume, more preferably 5% by volume or more, even more preferably 8% by volume or more, and even more preferably 10% by volume or more. When the thermoplastic resin (A) contains the thermoplastic resin (a2), the content of the thermoplastic resin (a2) in the thermoplastic resin (A) is, on a volume basis, preferably 55% by volume or less, more preferably 50% by volume or less, even more preferably 45% by volume or less, and even more preferably 40% by volume or less. If the content of the thermoplastic resin (a2) exceeds 0% by volume, it is easier to impart heat resistance to the adhesive for high-frequency dielectric heating. When the content of the thermoplastic resin (a2) is 55% by volume or less, the content of the styrene copolymer resin (a1) in the thermoplastic resin (A) increases, and therefore, when the thermoplastic resin (A) is bonded to an adherend containing a resin having an aromatic ring, for example, the adhesiveness to the adherend is likely to be improved.

[0040] The type of thermoplastic resin (a2) is not particularly limited. The thermoplastic resin (a2) may be used alone or in combination of two or more types, as long as it is a resin different from the styrene copolymer resin (a1). As described above, the thermoplastic resin (a2) is a resin different from the styrene copolymer resin (a1). Therefore, in this embodiment, the styrene resin as the thermoplastic resin (a2) does not include the styrene copolymer resin (a1). Hereinafter, in the description of the thermoplastic resin (a2), the styrene resin as the thermoplastic resin (a2) may be referred to as the styrene resin (a3) ​​for convenience.

[0041] From the viewpoints of ease of melting, heat resistance, etc., the thermoplastic resin (a2) is preferably at least one selected from the group consisting of polyolefin resins, polyolefin resins having a polar moiety, styrene resins (a3), polyacetal resins, polycarbonate resins, polyacrylic resins, polyamide resins, polyimide resins, polyvinyl acetate resins, phenoxy resins, polyester resins, polyphenylene sulfide resins, and polyphenylene ether resins.

[0042] Among the resins exemplified above, the thermoplastic resin (a2) is preferably a polyolefin resin or a polyphenylene ether resin, and more preferably a polyolefin resin. If the thermoplastic resin (a2) is a polyolefin resin or a polyphenylene ether resin, it will have high compatibility with the styrene copolymer resin (a1), making it easier to obtain high adhesive strength. Furthermore, if the thermoplastic resin (a2) is a polyolefin resin, the high-frequency dielectric heating adhesive will easily melt when a high-frequency electric field is applied, making it easier to obtain high adhesive strength. In this specification, polyolefin-based resins include polyolefin-based resins having polar moieties and polyolefin-based resins having no polar moieties, and when specifying whether or not a polar moiety is present, the resins are described as polyolefin-based resins having polar moieties or polyolefin-based resins having no polar moieties.

[0043] The thermoplastic resin (a2) is preferably a polyolefin resin having a polar moiety, but may also be a polyolefin resin having no polar moiety.

[0044] Polyolefin resin Examples of the polyolefin resin as the thermoplastic resin (a2) include resins made of homopolymers such as polyethylene, polypropylene, polybutene, and polymethylpentene, and α-olefin resins made of copolymers of monomers selected from the group consisting of ethylene, propylene, butene, hexene, octene, and 4-methylpentene. The polyolefin resin as the thermoplastic resin (a2) may be a single resin or a combination of two or more resins.

[0045] Polyolefin resin with polar moieties The polar moieties in the polyolefin resin having polar moieties are not particularly limited as long as they can impart polarity to the polyolefin resin. Polyolefin resins having polar moieties are preferred because they exhibit high adhesive strength to adherends. Furthermore, by including a polyolefin resin having polar moieties as the thermoplastic resin (a2) in the high-frequency dielectric heating adhesive, the dielectric properties tend to be improved, and the adhesive strength to adherends is also increased, which is preferred. The polyolefin-based thermoplastic resin having a polar moiety may be a copolymer of an olefin-based monomer and a monomer having a polar moiety, or may be a resin obtained by introducing a polar moiety into a polyolefin-based resin obtained by polymerization of an olefin-based monomer by modification such as an addition reaction.

[0046] The type of olefin monomer constituting the polyolefin resin having a polar moiety is not particularly limited. Examples of the olefin monomer include ethylene, propylene, butene, hexene, octene, and 4-methyl-1-pentene. The olefin monomer may be used alone or in combination of two or more. Of the olefin-based monomers, ethylene and propylene are preferred from the viewpoint of excellent mechanical strength and stable adhesive properties. The olefin-derived structural unit in the polyolefin-based resin having a polar moiety is preferably a structural unit derived from ethylene or propylene.

[0047] Examples of the polar moiety include a hydroxyl group, a carboxyl group, a vinyl acetate structure, an acid anhydride structure, etc. Examples of the polar moiety also include an acid-modified structure that is introduced into a polyolefin resin by acid modification.

[0048] The acid-modified structure as a polar moiety is a moiety introduced by acid-modifying a thermoplastic resin (e.g., a polyolefin-based resin). Compounds used to acid-modify a polyolefin-based resin include unsaturated carboxylic acid derivative components derived from unsaturated carboxylic acids, acid anhydrides of unsaturated carboxylic acids, and esters of unsaturated carboxylic acids. In this specification, a polyolefin-based resin having an acid-modified structure may be referred to as an acid-modified polyolefin-based resin.

[0049] Examples of unsaturated carboxylic acids include acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, and citraconic acid.

[0050] Examples of the acid anhydrides of unsaturated carboxylic acids include acid anhydrides of unsaturated carboxylic acids such as maleic anhydride, itaconic anhydride, and citraconic anhydride.

[0051] Examples of the esters of unsaturated carboxylic acids include esters of unsaturated carboxylic acids such as methyl acrylate, ethyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, dimethyl maleate, monomethyl maleate, dimethyl fumarate, diethyl fumarate, dimethyl itaconate, diethyl itaconate, dimethyl citraconate, diethyl citraconate, and dimethyl tetrahydrophthalic anhydride.

[0052] Styrene-based resin (a3) The styrene-based resin (a3) ​​as the thermoplastic resin (a2) may be a homopolymer of a styrene-based monomer (polystyrene: PS), such as a homopolymer of styrene, a homopolymer of α-methylstyrene, or a homopolymer of β-methylstyrene. The PS may be a general-purpose polystyrene resin (GPPS resin) or a high-impact polystyrene resin (HIPS resin). The high-impact polystyrene resin (HIPS resin) is a resin containing a GPPS resin and a rubber-like elastomer.

[0053] Polyphenylene ether resin The polyphenylene ether resin as the thermoplastic resin (a2) may be, for example, a polyphenylene ether homopolymer resin or a polyphenylene ether copolymer resin, or may be a modified polyphenylene ether resin, which is a polymer alloy of a polyphenylene ether resin and a resin other than a polyphenylene ether resin.

[0054] <Dielectric filler (B)> The high-frequency dielectric heating adhesive according to this embodiment may contain a dielectric filler (B), or may not contain a dielectric filler (B) as long as the desired dielectric properties are obtained.

[0055] The dielectric filler (B) is a filler that generates heat when a high-frequency electric field is applied. A high-frequency electric field is an electric field whose direction reverses at high frequencies. The dielectric filler (B) is preferably a filler that generates heat when a high-frequency electric field in the frequency range of 3 MHz or more and 300 MHz or less is applied to it. The dielectric filler (B) is preferably a filler that generates heat when a high-frequency electric field in the frequency range of 3 MHz or more and 300 MHz or less is applied to it, for example, a frequency of 13.56 MHz, 27.12 MHz, or 40.68 MHz.

[0056] The dielectric filler (B) is preferably an inorganic material having crystal water such as zinc oxide, silicon carbide (SiC), anatase type titanium oxide, barium titanate, barium titanate zirconate, lead titanate, potassium niobate, rutile type titanium oxide, hydrated aluminum silicate, hydrated aluminosilicate of an alkali metal, or an inorganic material having crystal water such as hydrated aluminosilicate of an alkaline earth metal, either alone or in combination of two or more.

[0057] The dielectric filler (B) preferably contains at least one selected from the group consisting of zinc oxide, silicon carbide, barium titanate, and titanium oxide, and more preferably contains at least one selected from the group consisting of zinc oxide, barium titanate, and titanium oxide.

[0058] Among the dielectric fillers listed above, zinc oxide is more preferred as the dielectric filler (B) because it is available in a wide variety of shapes and sizes, allowing for the adhesive properties and mechanical properties of the high-frequency dielectric heating adhesive to be improved to suit the application. By using zinc oxide as the dielectric filler (B), a colorless high-frequency dielectric heating adhesive can be obtained. Because zinc oxide has a low density among dielectric fillers, when adherends are bonded using a high-frequency dielectric heating adhesive containing zinc oxide as the dielectric filler (B), the total weight of the bonded body is less likely to increase compared to when adhesives containing other dielectric fillers are used. Zinc oxide is not too hard, even among ceramics, so it is less likely to damage the manufacturing equipment for the high-frequency dielectric heating adhesive. Because zinc oxide is an inactive oxide, it causes less damage to thermoplastic resins when blended with them. Furthermore, the titanium oxide as the dielectric filler (B) is preferably at least one of anatase type titanium oxide and rutile type titanium oxide, and from the viewpoint of excellent dielectric properties, anatase type titanium oxide is more preferable.

[0059] The volume content of the dielectric filler (B) in the high-frequency dielectric heating adhesive is preferably 5% by volume or more, more preferably 8% by volume or more, and even more preferably 10% by volume or more. The volume content of the dielectric filler (B) in the high-frequency dielectric heating adhesive is preferably 50% by volume or less, more preferably 40% by volume or less, even more preferably 35% by volume or less, and even more preferably 25% by volume or less. When the volume content of the dielectric filler (B) in the high-frequency dielectric heating adhesive is 5% by volume or more, heat generation is improved and it becomes easier to firmly bond the high-frequency dielectric heating adhesive to the adherend. By having the volume content of the dielectric filler (B) in the high-frequency dielectric heating adhesive be 50% by volume or less, it is possible to prevent a decrease in the strength of the adhesive, and as a result, by using this adhesive, it is possible to prevent a decrease in bonding strength. Furthermore, when the high-frequency dielectric heating adhesive according to this embodiment is an adhesive sheet, having the volume content of the dielectric filler (B) in the adhesive sheet be 50% by volume or less makes it easier to obtain flexibility as a sheet and to prevent a decrease in toughness, making it easier to process the high-frequency dielectric heating adhesive sheet into a desired shape in a subsequent process.

[0060] When the high-frequency dielectric heating adhesive according to this embodiment contains a thermoplastic resin (A) and a dielectric filler (B), the volume content of the dielectric filler (B) relative to the total volume of the thermoplastic resin (A) and the dielectric filler (B) is preferably 5% by volume or more, more preferably 8% by volume or more, and even more preferably 10% by volume or more. The volume content of the dielectric filler (B) relative to the total volume of the thermoplastic resin (A) and the dielectric filler (B) is preferably 50% by volume or less, more preferably 40% by volume or less, even more preferably 35% by volume or less, and even more preferably 25% by volume or less.

[0061] The volume average particle size of the dielectric filler (B) is preferably 1 μm or more, more preferably 2 μm or more, and even more preferably 3 μm or more. The volume average particle size of the dielectric filler (B) is preferably 30 μm or less, more preferably 25 μm or less, and even more preferably 20 μm or less. When the volume average particle diameter of the dielectric filler (B) is 1 μm or more, the high-frequency dielectric heating adhesive exhibits high heat-generating performance when a high-frequency electric field is applied, and the adhesive layer can be firmly bonded to the adherend in a short time. When the volume average particle diameter of the dielectric filler (B) is 30 μm or less, the high-frequency dielectric heating adhesive exhibits high heat-generating performance when a high-frequency electric field is applied, and the adhesive layer can be firmly bonded to the adherend in a short time. Furthermore, when the high-frequency dielectric heating adhesive according to this embodiment is an adhesive sheet, when the volume average particle diameter of the dielectric filler (B) is 30 μm or less, a decrease in the strength of the high-frequency dielectric heating adhesive sheet can be prevented.

[0062] The volume average particle diameter of the dielectric filler (B) is measured by the following method: The particle size distribution of the dielectric filler (B) is measured by a laser diffraction / scattering method, and the volume average particle diameter is calculated from the results of the particle size distribution measurement in accordance with JIS Z 8819-2:2001.

[0063] <Additives> The high-frequency dielectric heating adhesive according to this embodiment may or may not contain an additive.

[0064] When the high-frequency dielectric heating adhesive according to this embodiment contains an additive, examples of the additive include a tackifier, a plasticizer, a wax, a colorant, an antioxidant, an ultraviolet absorber, an antibacterial agent, a coupling agent, a viscosity modifier, an organic filler, an inorganic filler, etc. The organic filler and inorganic filler as additives are different from the dielectric filler.

[0065] Tackifiers and plasticizers can improve the melting and adhesive properties of the high frequency dielectric heating adhesive. Examples of tackifiers include rosin derivatives, polyterpene resins, aromatic modified terpene resins, hydrogenated aromatic modified terpene resins, terpene phenol resins, coumarone-indene resins, aliphatic petroleum resins, aromatic petroleum resins, and hydrogenated aromatic petroleum resins. Examples of plasticizers include petroleum-based process oils, natural oils, dialkyl dibasic acids, and low-molecular-weight liquid polymers. Examples of petroleum-based process oils include paraffin-based process oils, naphthenic process oils, and aromatic process oils. Examples of natural oils include castor oil and tall oil. Examples of dialkyl dibasic acids include dibutyl phthalate, dioctyl phthalate, and dibutyl adipate. Examples of low-molecular-weight liquid polymers include liquid polybutene and liquid polyisoprene.

[0066] When the high-frequency dielectric heating adhesive according to this embodiment contains an additive, the content of the additive in the high-frequency dielectric heating adhesive is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, and even more preferably 0.1% by mass or more, based on the total amount of the high-frequency dielectric heating adhesive. The content of the additive in the high-frequency dielectric heating adhesive is preferably 20% by mass or less, more preferably 15% by mass or less, and even more preferably 10% by mass or less.

[0067] The high-frequency dielectric heating adhesive according to this embodiment preferably does not contain a solvent. A solvent-free high-frequency dielectric heating adhesive is less likely to cause problems with VOCs (volatile organic compounds) that are caused by the adhesive used to bond the adhesive to the adherend.

[0068] The high-frequency dielectric heating adhesive according to this embodiment preferably does not contain conductive materials such as carbon or carbon compounds containing carbon as a main component (e.g., carbon black), metals, etc. The high-frequency dielectric heating adhesive according to this embodiment preferably does not contain, for example, carbon steel, α-iron, γ-iron, δ-iron, copper, iron oxide, brass, aluminum, iron-nickel alloy, iron-nickel-chromium alloy, carbon fiber, or carbon black.

[0069] When the high-frequency dielectric heating adhesive of this embodiment contains a conductive substance, the content of the conductive substance in the adhesive is, independently, preferably 7 mass% or less, based on the total amount of the adhesive, more preferably 6 mass% or less, even more preferably 5 mass% or less, even more preferably 1 mass% or less, and even more preferably 0.1 mass% or less. It is particularly preferable that the content of the conductive material in the adhesive is 0% by mass. If the content of the conductive substance in the adhesive is 7 mass % or less, it becomes easier to prevent the problem of carbonization of the bonded portion and the adherend due to electrical breakdown during dielectric heating treatment.

[0070] In the high-frequency dielectric heating adhesive according to this embodiment, the total content of the thermoplastic resin (A) and the dielectric filler (B) is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 93% by mass or more, even more preferably 95% by mass or more, and even more preferably 99% by mass or more.

[0071] <Characteristics of high frequency dielectric heating adhesive> Next, the characteristics of the high-frequency dielectric heating adhesive according to this embodiment will be described.

[0072] (tensile modulus) The tensile modulus of elasticity of the high frequency dielectric heating adhesive according to this embodiment will be described below. The high frequency dielectric heating adhesive according to this embodiment has a tensile modulus of elasticity of 20 MPa or more.

[0073] If the tensile modulus of the high-frequency dielectric heating adhesive is less than 20 MPa, the high-frequency dielectric heating adhesive is likely to break if an impact is applied to the structure when the high-frequency dielectric heating adhesive is joined to the adherend. Furthermore, the high-frequency dielectric heating adhesive becomes difficult to handle when joining the high-frequency dielectric heating adhesive to the adherend, resulting in poor processability. The upper limit of the tensile modulus of the high-frequency dielectric heating adhesive is not particularly limited and may be, for example, 2000 MPa or less. If the tensile modulus of the high-frequency dielectric heating adhesive is excessively high, for example, the processability of the high-frequency dielectric heating adhesive when cutting it to a predetermined size may be reduced.

[0074] The tensile modulus of elasticity of the high-frequency dielectric heating adhesive according to this embodiment is preferably 50 MPa or more, more preferably 100 MPa or more, even more preferably 200 MPa or more, even more preferably 500 MPa or more, even more preferably 750 MPa or more, and even more preferably 1000 MPa or more. The tensile modulus of elasticity of the adhesive for high-frequency dielectric heating according to this embodiment is preferably 1900 MPa or less, more preferably 1800 MPa or less, and even more preferably 1500 MPa or less. If the tensile modulus of the high-frequency dielectric heating adhesive is 50 MPa or more, damage to the high-frequency dielectric heating adhesive is more likely to be suppressed even if an impact is applied to the structure when the high-frequency dielectric heating adhesive is joined to the adherend. In addition, the high-frequency dielectric heating adhesive becomes easier to handle when joining the high-frequency dielectric heating adhesive to the adherend, and its processability is also improved. If the tensile modulus of the high-frequency dielectric heating adhesive is 1900 MPa or less, the structure obtained by joining the high-frequency dielectric heating adhesive to the adherend can be more easily processed when cut to predetermined dimensions.

[0075] (Tensile elongation at break) In the adhesive for high frequency dielectric heating according to this embodiment, the tensile elongation at break is preferably 5% or more, more preferably 10% or more, and even more preferably 20% or more. In the high-frequency dielectric heating adhesive according to this embodiment, the tensile elongation at break is preferably 1500% or less, more preferably 1000% or less, even more preferably 750% or less, even more preferably 500% or less, even more preferably 200% or less, and even more preferably 100% or less. If the tensile elongation at break of a high-frequency dielectric heating adhesive is 5% or more, the high-frequency dielectric heating adhesive is less likely to break when the high-frequency dielectric heating adhesive is joined to an adherend, even if an impact is applied to the structure. In addition, the high-frequency dielectric heating adhesive is easier to handle and process when joining the high-frequency dielectric heating adhesive to an adherend. If the tensile elongation at break is 1500% or less, the high-frequency dielectric heating adhesive can be easily processed when cut to predetermined dimensions.

[0076] In this specification, the tensile modulus of elasticity of the adhesive for high-frequency dielectric heating can be measured in accordance with JIS K 7161-1:2014 and JIS K 7127:1999. In addition, in this specification, the tensile elongation at break of the adhesive for high-frequency dielectric heating can be measured in accordance with JIS K 7161-1:2014 and JIS K 7127:1999.

[0077] (Dielectric properties) The dielectric properties (tan δ / ε'r) of the high frequency dielectric heating adhesive according to this embodiment will be described. The high frequency dielectric heating adhesive according to this embodiment has a dielectric property (tan δ / ε'r) of 0.005 or more. (tanδ is the dielectric tangent at 23°C and a frequency of 40.68MHz, ε'r is the relative permittivity at 23°C and a frequency of 40.68 MHz.)

[0078] If the dielectric properties of the high-frequency dielectric heating adhesive are 0.005 or higher, the high-frequency dielectric heating adhesive will easily generate heat when subjected to dielectric heating treatment, making it easier to firmly bond the high-frequency dielectric heating adhesive to the adherend in a short period of time.

[0079] The dielectric properties of the adhesive for high frequency dielectric heating according to this embodiment are more preferably 0.008 or more, and even more preferably 0.010 or more. If the dielectric properties of the high-frequency dielectric heating adhesive of this embodiment are 0.008 or higher, the high-frequency dielectric heating adhesive will be more likely to generate heat when subjected to dielectric heating treatment, making it easier to firmly bond the high-frequency dielectric heating adhesive to the adherend in a short period of time.

[0080] The upper limit of the dielectric properties of the high-frequency dielectric heating adhesive according to this embodiment is not particularly limited. The dielectric properties of the high-frequency dielectric heating adhesive according to this embodiment may be, for example, 0.1 or less, 0.08 or less, or 0.05 or less. The dielectric properties of the high-frequency dielectric heating adhesive may be, for example, 0.005 or more and 0.1 or less. If the dielectric characteristic of the high-frequency dielectric heating adhesive is 0.1 or less, overheating is easily suppressed, and damage to the contact area between the adherend and the high-frequency dielectric heating adhesive is less likely to occur.

[0081] The dielectric characteristic (tan δ / ε'r) is the value obtained by dividing the dielectric loss tangent (tan δ) measured using an impedance material apparatus or the like by the relative dielectric constant (ε'r) measured using an impedance material apparatus or the like. The dielectric properties of the adhesive for high frequency dielectric heating, that is, the dielectric loss tangent (tan δ) and the relative dielectric constant (ε'r), can be measured simply and accurately using an impedance material analyzer. The details of the method for measuring the dielectric properties of the high-frequency dielectric heating adhesive and the adherend are as follows: First, a measurement sheet of the high-frequency dielectric heating adhesive is obtained. If a measurement sheet needs to be obtained from a structure, a measurement sheet of uniform thickness is obtained by cutting or scraping it from the structure. For an unsheeted adhesive, for example, in pellet form, the measurement sheet is obtained by sheeting it using a heat press or the like. The thickness of the measurement sheet is, for example, 10 μm or more and 2 mm or less. The relative permittivity (ε'r) and dielectric loss tangent (tanδ) of the sheet obtained in this manner are measured using an RF Impedance Material Analyzer E4991A (manufactured by Agilent) at 23°C and a frequency of 40.68 MHz, and the value of the dielectric property (tanδ / ε'r) is calculated.

[0082] (Flow starting temperature) In the high-frequency dielectric heating adhesive according to this embodiment, the flow initiation temperature is preferably 80°C or higher, more preferably 100°C or higher, even more preferably 120°C or higher, and even more preferably 140°C or higher. In the high-frequency dielectric heating adhesive according to this embodiment, the flow initiation temperature is preferably 250°C or less, more preferably 220°C or less, even more preferably 200°C or less, and even more preferably 180°C or less. If the flow initiation temperature of the high-frequency dielectric heating adhesive is 80°C or higher, structures manufactured using the high-frequency dielectric heating adhesive are likely to have heat resistance suitable for everyday use. If the flow initiation temperature of the high-frequency dielectric heating adhesive is 250°C or lower, it is easy to prevent the time required to melt the high-frequency dielectric heating adhesive during bonding from being long, and it is also easy to obtain bonding strength between the high-frequency dielectric heating adhesive and the adherend. The flow initiation temperature can be measured by the method described in the Examples section below.

[0083] <Aspects of high frequency dielectric heating adhesive> The shape of the high-frequency dielectric heating adhesive according to this embodiment is not particularly limited, but is preferably in the form of a sheet. That is, the high-frequency dielectric heating adhesive according to this embodiment is preferably an adhesive sheet (sometimes referred to as a high-frequency dielectric heating adhesive sheet). When the high-frequency dielectric heating adhesive is an adhesive sheet, the time required for the manufacturing process of the structure can be further shortened.

[0084] In one aspect, the high-frequency dielectric heating adhesive according to this embodiment is composed of only one adhesive layer made of the high-frequency dielectric heating adhesive sheet according to this embodiment. When the high-frequency dielectric heating adhesive is a high-frequency dielectric heating adhesive sheet composed of only one adhesive layer, the adhesive layer itself corresponds to the high-frequency dielectric heating adhesive sheet, and the shape and characteristics of the high-frequency dielectric heating adhesive sheet correspond to the shape and characteristics of the adhesive layer. The high-frequency dielectric heating adhesive sheet preferably consists of only a single adhesive layer. The high-frequency dielectric heating adhesive according to this embodiment is preferably a high-frequency dielectric heating adhesive sheet composed of only a single adhesive layer. This allows the high-frequency dielectric heating adhesive sheet to be thin, and also makes it easy to mold the high-frequency dielectric heating adhesive sheet.

[0085] The high-frequency dielectric heating adhesive according to this embodiment is not limited to a high-frequency dielectric heating adhesive sheet consisting of only one adhesive layer. Another embodiment of the high-frequency dielectric heating adhesive may be a high-frequency dielectric heating adhesive sheet consisting of multiple layers. In this case, layers other than the adhesive layer may also be laminated.

[0086] Since a high-frequency dielectric heating adhesive sheet may consist of only one adhesive layer with high-frequency dielectric heating adhesive properties, in this specification the terms "high-frequency dielectric heating adhesive sheet" and "adhesive layer" may be interchangeable in some cases.

[0087] 1A, 1B, and 1C show schematic diagrams of a number of aspects of the high-frequency dielectric heating adhesive according to this embodiment.

[0088] The high-frequency dielectric heating adhesive 1A shown in FIG. 1A is an adhesive sheet consisting of only a single adhesive layer 10.

[0089] The high-frequency dielectric heating adhesive 1B shown in FIG. 1B is an adhesive sheet having an adhesive layer 10 and a substrate 30 that supports the adhesive layer 10. The adhesive layer 10 has a first surface 11. The substrate 30 is not particularly limited as long as it is a material that can support the adhesive layer 10. Examples of the substrate 30 include a resin sheet containing at least one resin selected from the group consisting of polyolefin resin, polyester resin, acetate resin, ABS resin, polystyrene resin, and vinyl chloride resin. Examples of polyolefin resins include polyethylene resin and polypropylene resin. Examples of polyester resins include polybutylene terephthalate resin and polyethylene terephthalate resin. The substrate 30 may contain a dielectric filler (B). The dielectric filler (B) in the adhesive layer 10 and the dielectric filler in the substrate 30 may be the same or different.

[0090] The high-frequency dielectric heating adhesive 1C shown in FIG. 1C is an adhesive sheet having an adhesive layer 10 and an intermediate layer 40 disposed between the adhesive layer 20. The high-frequency dielectric heating adhesive 1C has a first surface 11 and a second surface 21 opposite the first surface 11. In the high-frequency dielectric heating adhesive 1C, the adhesive layer 10 only needs to satisfy the requirements of the adhesive layer of the high-frequency dielectric heating adhesive sheet according to this embodiment. In one aspect, both the adhesive layer 10 and the adhesive layer 20 have the same composition and properties. In another aspect, the adhesive layer 20 is a high-frequency dielectric heating adhesive layer that differs from the adhesive layer 10 in at least one of its composition and properties. In another aspect, the adhesive layer 20 is a general adhesive layer that is not a high-frequency dielectric heating adhesive layer. In this case, the adhesive layer 20 that is not a high-frequency dielectric heating adhesive layer may be, for example, a layer of a drying-and-solidifying adhesive that dries and solidifies upon evaporation of water or a solvent, or a layer of an adhesive (pressure-sensitive adhesive) formed from an adhesive.

[0091] (Thickness) When the high-frequency dielectric heating adhesive of this embodiment is an adhesive sheet consisting of only one adhesive layer, the thickness of the adhesive sheet of this embodiment is preferably 5 μm or more, more preferably 10 μm or more, even more preferably 30 μm or more, and particularly preferably 50 μm or more. When the thickness of the adhesive sheet is 5 μm or more, the heat generation properties of the adhesive sheet in contact with the adherend when high frequency is applied are improved, making it easier to firmly bond the adhesive sheet and the adherend in a short time.In addition, when bonding to the adherend, the adhesive sheet can easily conform to the irregularities of the adherend, making it easier to develop adhesive strength.

[0092] When the adhesive sheet has a multilayer structure consisting of multiple layers, the thickness of the adhesive layer is preferably 5 μm or more, more preferably 10 μm or more, even more preferably 30 μm or more, and even more preferably 50 μm or more. When the adhesive sheet for high-frequency dielectric heating is a multi-layered sheet, if the thickness of the adhesive layer is 5 μm or more, the adhesive layer will easily conform to the unevenness of the adherend when adhering to the adherend, making it easier to develop adhesive strength.

[0093] The upper limit of the thickness of the adhesive sheet is not particularly limited. The thicker the adhesive sheet, the greater the weight of the entire structure obtained by adhering the adhesive sheet to the adherend. Therefore, it is preferable that the adhesive sheet have a thickness within a range that does not cause problems in practical use, such as processability and handling. Taking into consideration the practicality and formability of the high-frequency dielectric heating adhesive sheet, the thickness of the adhesive sheet according to this embodiment is preferably 2000 μm or less, more preferably 1000 μm or less, and even more preferably 600 μm or less. The upper limit of the adhesive sheet thickness is preferably the above value, regardless of whether the adhesive sheet has a single adhesive layer or a multilayer structure including multiple layers including the adhesive layer.

[0094] An adhesive sheet used as a high-frequency dielectric heating adhesive is easier to handle than a liquid adhesive that must be applied, and workability during bonding to an adherend is improved.

[0095] Furthermore, adhesive sheets used as high-frequency dielectric heating adhesives can be controlled in thickness and other dimensions as needed. This allows them to be used in roll-to-roll processes, and they can be processed into any desired area and shape by punching or other processes to match the bonding area with the adherend and the shape of the adherend. Therefore, adhesive sheets used as high-frequency dielectric heating adhesives have significant advantages from the perspective of the manufacturing process.

[0096] The high-frequency dielectric heating adhesive according to this embodiment is preferably used by applying a high-frequency electric field in the frequency range from so-called short wave to ultra-short wave (for example, 3 MHz or more to 300 MHz or less). When a high-frequency electric field in this frequency range is applied, the heatable depth is deep, improving the heat generation properties when high frequency is applied. Therefore, even if the high-frequency dielectric heating adhesive is thick, it is easy to firmly bond the adhesive sheet and the adherend in a short time. The high-frequency dielectric heating adhesive according to this embodiment is preferably used to bond to one or more adherends. The adherends will be described later.

[0097] An example of an index of fracture toughness of the high-frequency dielectric heating adhesive according to this embodiment is rectangular tear strength. In the high-frequency dielectric heating adhesive of this embodiment, the right-angle tear strength is preferably 15 N / mm or more, more preferably 20 N / mm or more, even more preferably 25 N / mm or more, even more preferably 30 N / mm or more, even more preferably 40 N / mm or more, and even more preferably 50 N / mm or more. If the right-angle tear strength of the high-frequency dielectric heating adhesive of this embodiment is 15 N / mm or more, even if a strong impact is applied to a structure obtained by joining the high-frequency dielectric heating adhesive and the adherend, destruction of the structure is more likely to be suppressed. The upper limit of the right-angle tear strength of the high-frequency dielectric heating adhesive according to this embodiment is not particularly limited, and may be, for example, 200 N / mm or less, or 100 N / mm or less.

[0098] <Method of manufacturing high frequency dielectric heating adhesive> The high-frequency dielectric heating adhesive according to this embodiment can be produced, for example, by mixing the above-mentioned components. When the high-frequency dielectric heating adhesive according to this embodiment is an adhesive sheet, the above-mentioned components can be premixed and kneaded using a known kneading device such as an extruder or a heated roll, and the adhesive can be produced by a known molding method such as extrusion molding, calendar molding, injection molding, or casting molding.

[0099] [Adherend] The material of the adherend is not particularly limited, and may be either an organic material or an inorganic material (including metal materials), or may be a composite material of an organic material and an inorganic material.

[0100] The material of the adherend is preferably an organic material. Examples of organic materials that can be used as the material of the adherend include plastic materials and rubber materials. Examples of plastic materials include polypropylene resin, polyethylene resin, epoxy resin, polyurethane resin, acrylonitrile-butadiene-styrene copolymer resin (ABS resin), polycarbonate resin (PC resin), polyamide resin (such as nylon 6 and nylon 66), polyester resin (such as polyethylene terephthalate (PET resin) and polybutylene terephthalate resin (PBT resin)), polyacetal resin (POM resin), polymethyl methacrylate resin, and styrene-based resin (such as polystyrene resin). Examples of rubber materials include styrene-butadiene rubber (SBR), ethylene propylene rubber (EPR), and silicone rubber. The adherend may also be a foamed organic material.

[0101] Examples of inorganic materials that can be used as the adherend include glass, cement, ceramic, and metal materials. The adherend may also be a fiber-reinforced plastic (FRP), a composite material made of fibers and the aforementioned plastic materials. The plastic material in the fiber-reinforced resin is at least one selected from the group consisting of polypropylene resin, polyethylene resin, polyurethane resin, acrylonitrile-butadiene-styrene copolymer resin (ABS resin), polycarbonate resin (PC resin), polyamide resin (such as nylon 6 and nylon 66), polyester resin (such as polyethylene terephthalate (PET resin) and polybutylene terephthalate resin (PBT resin)), polyacetal resin (POM resin), polymethyl methacrylate resin, and polystyrene resin. Examples of fibers in the fiber-reinforced resin include glass fiber, Kevlar fiber, and carbon fiber.

[0102] The adherend preferably has low electrical conductivity.

[0103] When one or more adherends are joined using the high-frequency dielectric heating adhesive according to this embodiment, the one or more adherends may be made of the same material or different materials. It is preferable that the material of at least one of the one or more adherends is primarily composed of a thermoplastic resin. In this specification, "primarily composed" means that the target substance is contained in the largest amount relative to the total. For example, this means that the target substance accounts for 50% by mass or more of the total.

[0104] When the material of at least one of the one or more adherends is primarily composed of a thermoplastic resin, it is preferable that at least one of the adherends contains a resin having an aromatic ring. Resins having an aromatic ring are resins containing an aromatic ring in the molecule, such as aromatic polyester resins (e.g., polyethylene terephthalate (PET) resin), aromatic polycarbonate resins (aromatic PC resins), polyphenylene sulfide resins (PPS resins), polyphenylene ether resins (PPE resins), and styrene-based resins (e.g., polystyrene resins). Among these, the resin having an aromatic ring is preferably a styrene-based resin. That is, the material of the adherend preferably contains a styrene-based resin, and more preferably contains a styrene-based resin as the primary component. When an adherend contains a styrene-based resin, excellent adhesion is achieved when bonded with the high-frequency dielectric heating adhesive according to this embodiment. When two or more adherends are bonded, the two or more adherends may contain the same resin having an aromatic ring or different resins having an aromatic ring. The two or more adherends may, for example, all contain a styrene-based resin. When the two or more adherends all contain a styrene-based resin, the two or more adherends may contain the same styrene-based resin or different styrene-based resins. Examples of the styrene-based resin used as the material for the adherend include the same resins as those described above for the styrene-based copolymer resin (a1) and thermoplastic resin (a2). Among the resins listed above, it is preferable to contain a homopolymer of a styrene-based monomer (polystyrene: PS). The adherend preferably contains, by mass, 50% or more of a resin having an aromatic ring, based on the total thermoplastic resin contained in the adherend, more preferably 60% or more, even more preferably 70% or more, and particularly preferably 80% or more.When the material of the adherend contains a styrene-based resin, an aromatic polyester resin, an aromatic polycarbonate resin, a polyphenylene sulfide resin, or a polyphenylene ether resin, the adherend preferably contains 50 mass % or more of the resin, more preferably 60 mass % or more, even more preferably 70 mass % or more, and even more preferably 80 mass % or more, of the total thermoplastic resin contained in the adherend.

[0105] The shape of the adherend is not particularly limited, but when the high-frequency dielectric heating adhesive according to this embodiment is an adhesive sheet, the adherend preferably has a surface to which the adhesive sheet can be attached, and is preferably in the form of a sheet or plate. When multiple adherends are to be bonded together, the shapes and dimensions of the adherends may be the same or different.

[0106] [Structure] The structure according to this embodiment includes the high-frequency dielectric heating adhesive according to this embodiment and one or more adherends. In the structure according to this embodiment, the one or more adherends are bonded with the high-frequency dielectric heating adhesive according to this embodiment. The structure according to this embodiment is preferably a structure (e.g., a laminate) in which one or more adherends are stacked via the high-frequency dielectric heating adhesive. The structure according to this embodiment may also be a structure in which two or more adherends are stacked via the high-frequency dielectric heating adhesive. Below, a case in which the structure according to this embodiment includes two adherends will be described with reference to the drawings.

[0107] FIG. 2 shows a schematic cross-sectional view of a structure 100 as an example of this embodiment. The structure 100 includes a first adherend 110, a second adherend 120, and a high-frequency dielectric heating adhesive 1A, with the high-frequency dielectric heating adhesive 1A being disposed between the first adherend 110 and the second adherend 120. The structure 100 is a laminate in which the first adherend 110, the high-frequency dielectric heating adhesive 1A, and the second adherend 120 are laminated in this order. The first adherend 110 and the second adherend 120 have the same dimensions in the thickness direction and length direction. The structure 100 is disposed in a position where the center portions of the first adherend 110, the high-frequency dielectric heating adhesive 1A, and the second adherend 120 are aligned in the length direction.

[0108] FIG. 3 shows a schematic cross-sectional view of a structure 200 as another example of this embodiment. The structure 200 includes a first adherend 210, a second adherend 220, and a high-frequency dielectric heating adhesive 1A, with the high-frequency dielectric heating adhesive 1A disposed between the first adherend 210 and the second adherend 220. The structure 200 is a laminate in which the first adherend 210, the high-frequency dielectric heating adhesive 1A, and the second adherend 220 are laminated in this order. The first adherend 210 has the same lengthwise dimension as the high-frequency dielectric heating adhesive 1A. The second adherend 220 has larger thickness and lengthwise dimensions than the first adherend 210. The first adherend 110 and the high-frequency dielectric heating adhesive 1A are disposed in positions where both longitudinal ends are aligned. The first adherend 110, the high-frequency dielectric heating adhesive 1A, and the second adherend 220 are disposed in positions where one longitudinal end of each is aligned.

[0109] When the structure according to this embodiment is a laminate, the material of the adherend in the laminate is preferably an organic material. When the laminate includes two or more adherends, the adherends may be made of the same material or different materials. Of the two or more adherends in the laminate, it is preferable that the material of at least one adherend mainly comprises a thermoplastic resin. Examples of the thermoplastic resin used as the adherend material include resins having an aromatic ring (e.g., styrene-based resins). Examples of the resins having an aromatic ring used as the adherend material include the resins exemplified above. Examples of the styrene-based resin used as the adherend material include resins similar to those described above for the styrene-based copolymer resin (a1) and the thermoplastic resin (a2). For example, in the structure 100 of FIG. 2, it is preferable that the materials of the first adherend 110 and the second adherend 120 as the outermost layers are organic materials. When the first adherend 110 and the second adherend 120 are made of an organic material, at least one of the first adherend 110 and the second adherend 120 preferably contains a resin having an aromatic ring (for example, a styrene-based resin). The same applies to the first adherend 210 and the second adherend 220 in the structure 200 of FIG. 3.

[0110] In the structure according to this embodiment, the position and thickness of the high-frequency dielectric heating adhesive are not limited to those shown in FIGS. In the structure according to this embodiment, the shape, size, number, etc. of the adherend are not limited to those shown in FIGS. The structure according to this embodiment is not limited to the structure in which two adherends are laminated together via a high-frequency dielectric heating adhesive as shown in FIGS.

[0111] [Method of manufacturing the structure] The method for manufacturing a structure according to this embodiment includes the steps of placing the high-frequency dielectric heating adhesive according to this embodiment on one or more adherends and applying a high-frequency electric field to the high-frequency dielectric heating adhesive to bond the one or more adherends. The frequency of the applied high-frequency electric field is, for example, 3 MHz or more and 300 MHz or less. When manufacturing a structure by bonding two or more adherends to the high-frequency dielectric heating adhesive according to this embodiment, the method for manufacturing a structure according to this embodiment includes the steps of placing the high-frequency dielectric heating adhesive according to this embodiment between the two or more adherends and applying a high-frequency electric field to the high-frequency dielectric heating adhesive to bond the two or more adherends. In this case, the frequency of the applied high-frequency electric field is, for example, 3 MHz or more and 300 MHz or less.

[0112] In the method for manufacturing a structure according to this embodiment, it is preferable to place two or more adherends and a high-frequency dielectric heating adhesive between electrodes of a dielectric heating device, and apply a high-frequency electric field while applying pressure to the two or more adherends and the high-frequency dielectric heating adhesive with the electrodes. By applying a high-frequency electric field while applying pressure with the electrodes in this manner, it becomes easier to manufacture a structure in a shorter time.

[0113] According to the manufacturing method using the high-frequency dielectric heating adhesive of this embodiment, it is possible to locally heat only predetermined locations from the outside using a dielectric heating device. Therefore, the manufacturing method using the high-frequency dielectric heating adhesive of this embodiment is effective even when the adherend is a large and complex three-dimensional structure or a thick and complex three-dimensional structure, etc., and even when high dimensional accuracy is required.

[0114] Below, as an example of a method for manufacturing a structure according to this embodiment, an embodiment in which two or more adherends are joined using the high-frequency dielectric heating adhesive according to this embodiment will be described, but the present invention is not limited to this embodiment.

[0115] The bonding method according to one aspect of this embodiment includes the following steps P1 and P2.

[0116] ·Process P1 Step P1 is a step of placing the high-frequency dielectric heating adhesive according to this embodiment between two or more adherends. When a laminate is produced as the structure according to this embodiment, in step P1, for example, the adherends and the high-frequency dielectric heating adhesive are alternately placed to stack the two or more adherends with the high-frequency dielectric heating adhesive interposed therebetween.

[0117] It is preferable to sandwich the high-frequency dielectric heating adhesive between the adherends so that the adherends can be joined together. The high-frequency dielectric heating adhesive may be sandwiched between a portion of the adherends, sandwiched between the adherends at multiple locations, or sandwiched over the entire surface of the adherends. From the viewpoint of improving the adhesive strength between the adherends, it is preferable to sandwich the high-frequency dielectric heating adhesive over the entire joining surface between the adherends. One embodiment of sandwiching the high-frequency dielectric heating adhesive between parts of the adherends is to arrange the high-frequency dielectric heating adhesive in a frame shape along the periphery of the joining surfaces of the adherends and sandwich the adhesive between the adherends. By arranging the high-frequency dielectric heating adhesive in a frame shape in this way, the joining strength between the adherends can be improved and the weight of the structure can be reduced compared to when the high-frequency dielectric heating adhesive is arranged over the entire joining surface. Furthermore, according to one embodiment in which high-frequency dielectric heating adhesive is sandwiched between a portion of the adherends, the amount of high-frequency dielectric heating adhesive used can be reduced and the size can be made smaller, thereby shortening the high-frequency dielectric heating processing time compared to when high-frequency dielectric heating adhesive is placed over the entire joining surface.

[0118] ·Process P2 Step P2 is a step of applying a high-frequency electric field to the high-frequency dielectric heating adhesive placed between the adherends in step P1 to bond two or more adherends. In one embodiment, the frequency of the applied high-frequency electric field is 3 MHz or more and 300 MHz or less. For example, a dielectric heating device can be used to apply the high-frequency electric field to the high-frequency dielectric heating adhesive.

[0119] (Dielectric heating device) FIG. 4 shows a schematic diagram illustrating a high-frequency dielectric heating process using the high-frequency dielectric heating adhesive and dielectric heating device according to this embodiment. The dielectric heating device 50 shown in FIG. 4 includes a first high-frequency electric field applying electrode 51, a second high-frequency electric field applying electrode 52, and a high-frequency power supply 53. The first high-frequency electric field applying electrode 51 and the second high-frequency electric field applying electrode 52 are arranged opposite to each other. The first high-frequency electric field applying electrode 51 and the second high-frequency electric field applying electrode 52 have a pressing mechanism. The pressing mechanism of the electrodes (first high-frequency electric field applying electrode 51 and second high-frequency electric field applying electrode 52) of the dielectric heating device 50 can also apply a high-frequency electric field while applying pressure to two or more adherends and the high-frequency dielectric heating adhesive placed between the electrodes.

[0120] 4 shows an example of a method for producing a structure 100 (see FIG. 2) using a dielectric heating device 50. The dielectric heating device 50 can apply pressure to a first adherend 110, a high-frequency dielectric heating adhesive 1A, and a second adherend 120 between a first high-frequency electric field application electrode 51 and a second high-frequency electric field application electrode 52.

[0121] When the first high-frequency electric field applying electrode 51 and the second high-frequency electric field applying electrode 52 form a pair of parallel plate electrodes, this type of electrode arrangement is sometimes called a parallel plate type. It is also preferable to use a parallel plate type high frequency dielectric heating device to apply the high frequency electric field. With a parallel plate type high frequency dielectric heating device, the high frequency electric field penetrates the high frequency dielectric heating adhesive located between the electrodes, so the entire high frequency dielectric heating adhesive can be heated and the adherend and the high frequency dielectric heating adhesive can be bonded in a short time. Furthermore, when manufacturing a laminate as a structure, it is preferable to use a parallel plate type high frequency dielectric heating device.

[0122] A high frequency power supply 53 is connected to each of the first high frequency electric field applying electrode 51 and the second high frequency electric field applying electrode 52 to apply a high frequency electric field of, for example, about 13.56 MHz, about 27.12 MHz, or about 40.68 MHz. 4, the dielectric heating device 50 performs a dielectric heating process via a high-frequency dielectric heating adhesive 1A sandwiched between a first adherend 110 and a second adherend 120. In addition to the dielectric heating process, the dielectric heating device 50 also bonds the first adherend 110 and the second adherend 120 by a pressure process using a first high-frequency electric field application electrode 51 and a second high-frequency electric field application electrode 52. Note that two or more adherends may be bonded without the pressure process, for example, by pressing only with the high-frequency dielectric heating adhesive or the weight of the adherends.

[0123] When a high-frequency electric field is applied between the first high-frequency electric field application electrode 51 and the second high-frequency electric field application electrode 52, the high-frequency dielectric heating adhesive 1A absorbs the high-frequency energy. This causes the thermoplastic resin component in the high-frequency dielectric heating adhesive 1A to melt, allowing the first adherend 110 and the second adherend 120 to be firmly bonded together even in a short period of time. If the high-frequency dielectric heating adhesive 1A contains a dielectric filler (not shown), the dielectric filler dispersed in the adhesive component absorbs high-frequency energy. The dielectric filler then functions as a heat source, and the heat generated by the dielectric filler melts the thermoplastic resin component, ultimately firmly bonding the first adherend 110 and the second adherend 120 together, even after a short treatment time.

[0124] The first high-frequency electric field applying electrode 51 and the second high-frequency electric field applying electrode 52 have a pressing mechanism, and therefore also function as a pressing device. Therefore, the first adherend 110 and the second adherend 120 can be more firmly joined by the compression direction pressure applied by the first high-frequency electric field applying electrode 51 and the second high-frequency electric field applying electrode 52 and the heating and melting of the high-frequency dielectric heating adhesive 1A. Note that, although the method for manufacturing the structure has been described using an example in which the structure 100 shown in FIG. 2 is manufactured, the present invention is not limited to this example.

[0125] (High frequency dielectric heating conditions) The high-frequency dielectric heating conditions can be changed as appropriate, but the following conditions are preferred.

[0126] The output of the high frequency electric field is preferably 10 W or more, more preferably 30 W or more, even more preferably 50 W or more, and even more preferably 80 W or more. The output of the high frequency electric field is preferably 50,000 W or less, more preferably 20,000 W or less, even more preferably 15,000 W or less, even more preferably 10,000 W or less, and even more preferably 1,000 W or less. If the output of the high frequency electric field is 10 W or more, the problem of the temperature not rising easily during the dielectric heating process can be prevented, and good bonding strength can be easily obtained. If the output of the high frequency electric field is 50,000 W or less, it is easy to prevent the problem of temperature control becoming difficult during dielectric heating treatment.

[0127] The application time of the high frequency electric field is preferably 1 second or more. The application time of the high-frequency electric field is preferably 300 seconds or less, more preferably 240 seconds or less, even more preferably 180 seconds or less, even more preferably 120 seconds or less, even more preferably 90 seconds or less, and particularly preferably 50 seconds or less. If the application time of the high frequency electric field is 1 second or more, the problem of the temperature not rising easily during the dielectric heating process can be prevented, and good adhesive strength can be easily obtained. If the application time of the high frequency electric field is 300 seconds or less, it is easy to prevent problems such as a decrease in the manufacturing efficiency of the structure, an increase in manufacturing costs, and thermal deterioration of the adherend.

[0128] The frequency of the applied high frequency electric field is more preferably 1 kHz or higher, more preferably 1 MHz or higher, more preferably 3 MHz or higher, even more preferably 5 MHz or higher, and even more preferably 10 MHz or higher. The frequency of the applied high-frequency electric field is preferably 300 MHz or less, more preferably 100 MHz or less, even more preferably 80 MHz or less, and even more preferably 50 MHz or less. Specifically, the industrial frequency bands of 13.56 MHz, 27.12 MHz, and 40.68 MHz assigned by the International Telecommunication Union are also used in the manufacturing method and joining method using high-frequency dielectric heating of this embodiment.

[0129] [Effects of this embodiment] The high-frequency dielectric heating adhesive of this embodiment contains a thermoplastic resin (A) containing a styrene copolymer resin (a1) and has a tensile modulus that satisfies a specific lower limit, thereby improving the strength characteristics of the high-frequency dielectric heating adhesive. Furthermore, when the adherend contains a styrene resin, the adhesive can be more firmly bonded to the adherend. Furthermore, since the high-frequency dielectric heating adhesive of this embodiment has dielectric properties that satisfy the lower limit, it can firmly bond one or more adherends at a time in a short period of time. According to this embodiment, it is possible to provide a structure in which one or more adherends are bonded with the high-frequency dielectric heating adhesive, and a method for manufacturing the structure. According to the method for manufacturing the structure, a structure in which one or more adherends are bonded can be manufactured in a short period of time.

[0130] The high-frequency dielectric heating adhesive according to this embodiment has excellent fracture toughness. Therefore, by using the high-frequency dielectric heating adhesive according to this embodiment, a structure formed by bonding the high-frequency dielectric heating adhesive to an adherend exhibits little loss in strength even when subjected to a strong impact. Assuming that an impact bond strength test is conducted on a structure having a shape such as structure 200 shown in FIG. 3, for example, high impact bond strength is expected to be obtained. This is thought to be because, for example, if a crack exists in the high-frequency dielectric heating adhesive, cracks occurring in the structure will be less likely to propagate from this crack as a starting point.

[0131] High frequency dielectric heating adhesives have superior water resistance and moisture resistance compared to general pressure sensitive adhesives.

[0132] The high-frequency dielectric heating adhesive according to this embodiment is locally heated by the application of a high-frequency electric field, which makes it easy to prevent the entire adherend from being damaged when the adhesive is bonded to the adherend.

[0133] [Modifications of the embodiment] The present invention is not limited to the above-described embodiment, and may include modifications and improvements within the scope of achieving the object of the present invention.

[0134] The high-frequency dielectric heating process is not limited to the dielectric heating device with opposing electrodes described in the above embodiment, and a grid-type high-frequency dielectric heating device may also be used. A grid-type high-frequency dielectric heating device has a grid electrode in which electrodes of a first polarity and electrodes of a second polarity opposite to the first polarity are alternately arranged at regular intervals on the same plane. For simplicity, the figures show an example using a dielectric heating device with opposing electrodes. [Example]

[0135] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples in any way.

[0136] [Preparation of adhesive for high frequency dielectric heating] (Examples 1 to 5 and Comparative Examples 1 to 4) Materials for producing a high-frequency dielectric heating adhesive (adhesive sheet) were premixed according to the composition shown in Table 1. In Table 1, the high-frequency dielectric heating adhesive sheet is referred to as adhesive sheet. The premixed materials were fed into the hopper of a 30 mm diameter twin-screw extruder, and the cylinder temperature and die temperature were adjusted appropriately according to the type of thermoplastic resin (A), followed by melt-kneading the premixed materials. The melt-kneaded materials were cooled and then cut to produce granular pellets. The produced granular pellets were then fed into the hopper of a single-screw extruder equipped with a T-die, and the cylinder temperature and die temperature were adjusted appropriately according to the type of thermoplastic resin (A). A film-like melt-kneaded material was extruded from the T-die and cooled on a cooling roll, producing 400 μm-thick sheet-like high-frequency dielectric heating adhesives (high-frequency dielectric heating adhesive sheets) according to Examples 1 to 5 and Comparative Examples 1 to 4.

[0137] The thermoplastic resin (A) and the dielectric filler (B) shown in Table 1 are explained as follows: In Table 1, the content of the styrene-based monomer unit is expressed as the st monomer amount.

[0138] -Thermoplastic resin (A)- Styrene copolymer resin (a1) SEBS-1: Styrene-ethylene / butylene-styrene copolymer (manufactured by Asahi Kasei Corporation, product name "Tuftec H1043", styrene monomer unit content 67% by mass) SEBS-2: Styrene-ethylene / butylene-styrene copolymer (manufactured by Asahi Kasei Corporation, product name "Tuftec H1053", styrene monomer unit content 29% by mass) SEBS-3: Styrene-ethylene / butylene-styrene copolymer (manufactured by Sumitomo Chemical Co., Ltd., product name "ESPOLEX SB-2400") SBS: Styrene-butadiene-styrene copolymer (manufactured by Asahi Kasei Corporation, product name "Tufprene 126S", styrene monomer unit content 40% by mass) SIS: styrene-isoprene-styrene copolymer (manufactured by Zeon Corporation, product name "Quintac 3390", styrene monomer unit content 48% by mass)

[0139] SEBS-1, SEBS-2, and SEBS-3 are hydrogenated styrene copolymer resins, while SBS and SIS are unhydrogenated styrene copolymer resins.

[0140] Other thermoplastic resins (a2) GPPS: General-purpose polystyrene resin (manufactured by PS Japan Co., Ltd., product name "HF77", styrene monomer unit content 100% by mass) Random PP: Random polypropylene resin (Prime Polymer Co., Ltd., product name "Prime Polypro J705UG", styrene monomer unit content 0% by mass)

[0141] -Dielectric filler (B)- ZnO: Zinc oxide (manufactured by Sakai Chemical Industry Co., Ltd., product name "LP-ZINC11").

[0142] (Volume average particle size of dielectric filler) The particle size distribution of the dielectric filler was measured by laser diffraction / scattering. The volume average particle diameter was calculated from the particle size distribution measurement results in accordance with JIS Z 8819-2:2001. The calculated volume average particle diameter of zinc oxide (ZnO) was 11 μm.

[0143] ·Adherent General-purpose polystyrene resin sheet (manufactured by Kyoei Resin Co., Ltd., product name "Dearite PS 201B-W1001").

[0144] [Evaluation of high frequency dielectric heating adhesive] The high-frequency dielectric heating adhesive (adhesive sheet) was evaluated as follows. The evaluation results are shown in Table 2.

[0145] (tensile modulus, tensile elongation at break) The prepared high-frequency dielectric heating adhesive sheet was cut into test pieces 150 mm long (TD direction) and 15 mm wide (MD direction). The test pieces were clamped between the chucks of a testing machine, and the tensile modulus (MPa) and tensile elongation at break (%) were measured at 23°C in accordance with JIS K 7161-1:2014 and JIS K 7127:1999. The tensile modulus (MPa) and tensile elongation at break (%) were measured using a tensile testing machine (Shimadzu Corporation, Autograph AG-IS 500N). The chuck distance was set to 100 mm. The tensile speed for measuring the tensile modulus (MPa) and tensile elongation at break (%) was 200 mm / min.

[0146] (Dielectric properties) The prepared adhesive sheet for high-frequency dielectric heating was cut into a length of 30 mm and a width of 30 mm. The dielectric constant (ε'r) and dielectric loss tangent (tanδ) of the cut adhesive sheet for high-frequency dielectric heating were measured using the parallel plate method at a frequency of 40.68 MHz at 23°C using an RF Impedance Material Analyzer E4991A (Agilent). The dielectric properties (tanδ / ε'r) were calculated based on the measurement results.

[0147] (Flow starting temperature) The flow initiation temperature of the fabricated high-frequency dielectric heating adhesive sheet was measured using a drop-type flow tester (Shimadzu Corporation, model number "CFT-100D"). Using a 5.0 kg load, a die with a 2.0 mm diameter hole and a 5.0 mm length, and a cylinder with an inner diameter of 11.329 mm, the temperature of the measurement sample was increased at a rate of 10°C / min over a temperature range of 30°C to 300°C. The stroke displacement rate (mm / min) was measured as it varied with the temperature rise, and a temperature dependence chart of the sample's stroke displacement rate was obtained. The flow initiation temperature was determined from this chart. The temperature at which the stroke displacement rate began to increase again after passing the peak on the low-temperature side of the chart was taken as the flow initiation temperature.

[0148] (Right-angle tear test) The adhesive sheet for high-frequency dielectric heating thus prepared was punched to obtain test specimens with the shape and dimensions specified in JIS K 7128-3:1998. The tear strength of the adhesive sheet for high-frequency dielectric heating was measured using a rectangular tear tester (Shimadzu Corporation, Autograph AG-IS 500N) in accordance with the JIS standard. The rectangular tear strength was measured using a tensile tester (Shimadzu Corporation, Autograph AG-IS 500N). The clamped portion of the test specimen was attached to the clamping tool of the tester, and the specimen was pulled at a tensile speed of 200 mm / min, and the maximum load F (N) was read. The rectangular tear strength T (N / mm) was calculated by dividing the maximum load F by the thickness d (mm) of the specimen (rectangular tear strength T = maximum load F / specimen thickness d).

[0149] (Weather resistance test) For the weather resistance test, a test specimen having the same shape and dimensions as the test specimen for the above-mentioned right-angle tear test was prepared separately. The prepared test specimen was subjected to a weather resistance test using an ultra-accelerated weather resistance tester (Iwasaki Electric Co., Ltd., Eye Super UV Tester SUV-W161). The test conditions were as follows: a metal halide lamp was used, and the illuminance was 90 mW / cm. 2 The irradiation time was 48 hours, the black panel temperature during irradiation was 63°C, and the relative humidity in the chamber was 70%RH. The test pieces after irradiation were subjected to the rectangular tear test described above. In addition, since the test pieces of Examples 4 and 5 deteriorated due to the weather resistance test, it was not possible to carry out a rectangular tear test after the weather resistance test. In addition, since the adhesiveness of Comparative Examples 2, 3, and 4 was evaluated as F, which will be described later, a rectangular tear test after the weather resistance test was not carried out.

[0150] (Adhesiveness) First, the high-frequency dielectric heating adhesive (adhesive sheet) was cut to a length of 25 mm and a width of 12.5 mm. Two of the aforementioned polystyrene resin sheets were prepared as adherends, each cut to a length of 25 mm, a width of 100 mm, and a thickness of 2 mm. The adhesive sheet cut to the aforementioned size was placed between the two adherends and laminated. Next, the adherend and adhesive sheet thus laminated were fixed between the two electrodes of a high-frequency dielectric heating device (Yamamoto Vinita Co., Ltd., product name "YRP-400T-A"). In this fixed state, a high-frequency electric field was applied under the following high-frequency application conditions to bond the high-frequency dielectric heating adhesive sheet and the adherend, thereby producing a test piece for adhesiveness evaluation. The pressing pressure when the high-frequency electric field was applied was the initial setting value for the pressure applied to the adhesive sheet.

[0151] High frequency electric field application conditions Frequency: 40.68MHz Output: 250W Application time: 20 seconds Pressing pressure: 0.52 MPa

[0152] The tensile shear strength (unit: MPa) was measured as adhesive strength for the obtained test pieces. A universal tensile tester (Instron 5581, manufactured by Instron Corporation) was used to measure the tensile shear strength. The tensile speed in measuring the tensile shear strength was set at 100 mm / min. The measurement of the tensile shear strength was in accordance with JIS K 6850:1999.

[0153] The adhesiveness of the prepared test pieces for adhesiveness evaluation was evaluated according to the following criteria. A: The bond strength is 1 MPa or more, or the adherend breaks. F: The bond strength is less than 1 MPa, or peeling occurs at the interface between the adhesive sheet and the adherend. The bonding strength of all the test pieces for evaluation was 1 MPa or more.

[0154] [Table 1]

[0155] [Table 2]

[0156] The adhesive properties and rectangular tear strength of each example were superior to those of each comparative example. These results demonstrate that the high-frequency dielectric heating adhesive according to this embodiment allows for bonding in a short time and provides a high-frequency dielectric heating adhesive with improved fracture toughness. [Explanation of symbols]

[0157] 10, 20... adhesive layer, 11... first surface, 21... second surface, 30... substrate, 40... intermediate layer, 100, 200... structure, 1A, 1B, 1C... high frequency dielectric heating adhesive, 50... dielectric heating device, 51... first high frequency electric field application electrode, 52... second high frequency electric field application electrode, 53... high frequency power supply, 110, 210... first adherend, 120, 220... second adherend

Claims

1. A high-frequency dielectric heating adhesive, The high-frequency dielectric heating adhesive contains a thermoplastic resin (A) and a dielectric filler (B) that generates heat upon application of a high-frequency electric field, The thermoplastic resin (A) contains a styrene copolymer resin (a1), the content of the styrene copolymer resin (a1) in the thermoplastic resin (A) is 40% by volume or more and 100% by volume or less, the content of styrene-based monomer units in the styrene-based copolymer resin (a1) is 10% by mass or more and 90% by mass or less, the styrene copolymer resin (a1) is a styrene elastomer, The tensile modulus of the high-frequency dielectric heating adhesive is 20 MPa or more, The dielectric characteristic (tanδ / ε′r) of the high-frequency dielectric heating adhesive is 0.005 or more. Adhesive for high frequency dielectric heating. (tanδ is the dielectric loss tangent at 23°C and a frequency of 40.68 MHz, ε'r is the relative dielectric constant at 23°C and a frequency of 40.68 MHz.)

2. The dielectric filler (B) is at least one selected from the group consisting of zinc oxide, silicon carbide, titanium oxide, and barium titanate. The high-frequency dielectric heating adhesive according to claim 1.

3. The flow starting temperature of the high-frequency dielectric heating adhesive is 80°C or higher and 250°C or lower. The adhesive for high-frequency dielectric heating according to claim 1 or 2.

4. The styrene copolymer resin (a1) is a hydrogenated resin. The adhesive for high-frequency dielectric heating according to any one of claims 1 to 3.

5. The thermoplastic resin (A) is a thermoplastic resin different from the styrene copolymer resin (a1). Further containing fat (a2), The adhesive for high-frequency dielectric heating according to any one of claims 1 to 4.

6. the content of the styrene copolymer resin (a1) is 20% by volume or more and 98% by volume or less with respect to the entire high-frequency dielectric heating adhesive; The adhesive for high-frequency dielectric heating according to any one of claims 1 to 5.

7. The high-frequency dielectric heating adhesive is used by applying a high-frequency electric field of 3 MHz or more and 300 MHz or less. The adhesive for high-frequency dielectric heating according to any one of claims 1 to 6.

8. The high-frequency dielectric heating adhesive is an adhesive for joining one or more adherends, At least one of the one or more adherends contains a resin having an aromatic ring. The adhesive for high-frequency dielectric heating according to any one of claims 1 to 7.

9. The resin having an aromatic ring is a styrene-based resin. The high-frequency dielectric heating adhesive according to claim 8.

10. The high-frequency dielectric heating adhesive is an adhesive sheet. The adhesive for high-frequency dielectric heating according to any one of claims 1 to 9.

11. The thickness of the adhesive sheet is 5 μm or more and 2000 μm or less. The high-frequency dielectric heating adhesive according to claim 10.

12. One or more adherends are bonded with the high-frequency dielectric heating adhesive according to any one of claims 1 to 11. structure.

13. A step of placing the high-frequency dielectric heating adhesive according to any one of claims 1 to 11 on one or more adherends; and applying a high-frequency electric field of 3 MHz or more and 300 MHz or less to the high-frequency dielectric heating adhesive to bond the adherend. Method for manufacturing the structure.

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