Adhesive for high-frequency dielectric heating and structure

Abstract

An adhesive (1A) for high-frequency dielectric heating contains: (A) a thermoplastic resin containing a styrene-based thermoplastic elastomer (a1) and a thermoplastic resin (a2) other than the styrene-based thermoplastic elastomer (a1); and (B) a dielectric filler. The content of the styrene component with respect to the entirety of the thermoplastic resin (A) is 20.0-45.0 mass%, the storage elastic modulus in an environment at 110°C is 300 MPa or more, and the complex viscosity at a shear rate of 600 rad / s in an environment of 220°C is 350Pa·s or less.

Description

High frequency dielectric heating adhesive and structure

[0001] The present invention relates to an adhesive and a structure for high frequency dielectric heating.

[0002] As a method for bonding adherends using an adhesive, a method for bonding adherends by high frequency dielectric heating or the like has been proposed.

[0003] Patent Document 1 discloses a high-frequency dielectric heating adhesive containing a thermoplastic resin (A), the thermoplastic resin (A) containing 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, and 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 disclosed in Patent Document 1 has a tensile modulus of elasticity of 20 MPa or more and a dielectric property (tan δ / ε'r) of 0.005 or more.

[0004] International Publication No. 2021 / 201173

[0005] A high-frequency dielectric heating adhesive may be used to bond an adherend containing, for example, a styrene-based resin. In this case, the high-frequency dielectric heating adhesive may be required to have excellent adhesion to an adherend containing a styrene-based resin, even in a high-temperature environment. Furthermore, the high-frequency dielectric heating adhesive may be required to have excellent adhesion to an adherend containing a styrene-based resin, even in a room temperature environment and a low-temperature environment below 0°C. Furthermore, the high-frequency dielectric heating adhesive may be required to have a complex shape. To produce a high-frequency dielectric heating adhesive with a complex shape, the high-frequency dielectric heating adhesive may be produced by, for example, injection molding. For this reason, the high-frequency dielectric heating adhesive may be required to have excellent adhesion to an adherend containing a styrene-based resin, and to be suitable for injection molding, under both environmental conditions, such as (1) a high-temperature environment and (2) an environment around room temperature. Therefore, there is room for further improvement in high-frequency dielectric heating adhesives to meet the demand for both excellent adhesion and excellent injection moldability.

[0006] The object of the present invention is to provide a high-frequency dielectric heating adhesive containing a thermoplastic resin and a dielectric filler, which has superior injection moldability compared to conventional high-frequency dielectric heating adhesives, and which has excellent adhesion to adherends regardless of environmental conditions, even when the adherend contains a styrene-based resin, and a structure comprising said high-frequency dielectric heating adhesive.

[0007] [1] A high-frequency dielectric heating adhesive, comprising: a thermoplastic resin (A) containing a styrene-based thermoplastic elastomer (a1) and a thermoplastic resin (a2) other than the styrene-based thermoplastic elastomer (a1); and a dielectric filler (B), wherein the content of the styrene component in the entire thermoplastic resin (A) is 20.0 mass% or more and 45.0 mass% or less, the storage modulus in an environment of 110°C is 300 MPa or more, and the complex viscosity in an environment of 220°C at a shear rate of 600 rad / s is 350 Pa s or less.

[0008] [2] The adhesive for high-frequency dielectric heating according to [1], wherein the thermoplastic resin (a2) is a polyolefin resin.

[0009] [3] The adhesive for high-frequency dielectric heating according to [1] or [2], wherein the styrene-based thermoplastic elastomer (a1) contains a hydrogenated product of a styrene-based copolymer resin.

[0010] [4] The adhesive for high-frequency dielectric heating according to any one of [1] to [3], wherein the styrene-based thermoplastic elastomer (a1) contains styrene-(ethylene / butylene)-styrene.

[0011] [5] The adhesive for high-frequency dielectric heating according to any one of [1] to [4], wherein the thermoplastic resin (a2) contains a polypropylene-based resin.

[0012] [6] The high-frequency dielectric heating adhesive according to any one of [1] to [5], wherein the content of the styrene-based thermoplastic elastomer (a1) is 15.0 vol% or more and 55.0 vol% or less, based on the total volume of the high-frequency dielectric heating adhesive.

[0013] [7] The high-frequency dielectric heating adhesive according to any one of [1] to [6], wherein the content of the thermoplastic resin (a2) is 25.0 vol% or more and 65.0 vol% or less, based on the total volume of the high-frequency dielectric heating adhesive.

[0014] [8] The high-frequency dielectric heating adhesive according to any one of [1] to [7], wherein the content of the dielectric filler (B) is 3.0% by volume or more and 40.0% by volume or less, based on the total volume of the high-frequency dielectric heating adhesive.

[0015] [9] The high-frequency dielectric heating adhesive according to any one of [1] to [8], wherein the dielectric filler (B) is at least one selected from the group consisting of zinc oxide, silicon carbide, and titanium oxide.

[0016]

[10] The high-frequency dielectric heating adhesive according to any one of [1] to [9], wherein the high-frequency dielectric heating adhesive is a high-frequency dielectric heating adhesive sheet.

[0017]

[11] The high-frequency dielectric heating adhesive according to any one of [1] to

[10] , wherein the high-frequency dielectric heating adhesive is an injection-molded article.

[0018]

[12] A structure comprising: the high-frequency dielectric heating adhesive according to any one of [1] to

[11] ; and an adherend containing a styrene-based resin, wherein the adherend is bonded by the high-frequency dielectric heating adhesive.

[0019] According to one aspect of the present invention, a high-frequency dielectric heating adhesive containing a thermoplastic resin and a dielectric filler has superior injection moldability compared to conventional high-frequency dielectric heating adhesives, and has excellent adhesion to adherends regardless of environmental conditions, even when the adherend contains a styrene-based resin, and a structure comprising this high-frequency dielectric heating adhesive can be provided.

[0020] FIG. 1 is a schematic cross-sectional view showing an example of a high-frequency dielectric heating adhesive according to the present embodiment; FIG. 2 is a schematic cross-sectional view showing another example of a high-frequency dielectric heating adhesive according to the present embodiment; FIG. 3 is a schematic cross-sectional view showing another example of a high-frequency dielectric heating adhesive according to the present embodiment; FIG. 4 is a schematic cross-sectional view showing an example of a structure according to the present embodiment; FIG. 5 is a schematic view illustrating an example of a high-frequency dielectric heating treatment using the high-frequency dielectric heating adhesive according to the present embodiment and a dielectric heating device; and FIG. 6 is a schematic plan view showing the shape of the high-frequency dielectric heating adhesives produced in the examples and comparative examples.

[0021] An example of a preferred embodiment of the present invention will be described below.

[0022] [High-frequency dielectric heating adhesive] The high-frequency dielectric heating adhesive according to this embodiment contains a thermoplastic resin (A) including a styrene-based thermoplastic elastomer (a1) and a thermoplastic resin (a2) other than the styrene-based thermoplastic elastomer (a1), and a dielectric filler (B). The content of the styrene component in the entire thermoplastic resin (A) is 20.0 mass% or more and 45.0 mass% or less. The adhesive has a storage modulus of 300 MPa or more at 110°C and a complex viscosity of 350 Pa s or less at 220°C and a shear rate of 600 rad / s.

[0023] The high-frequency dielectric heating adhesive according to the present embodiment, having the above-described configuration, exhibits superior injection moldability compared to conventional high-frequency dielectric heating adhesives. It also exhibits excellent adhesion to adherends containing styrene-based resins, regardless of environmental conditions. The inventors discovered that the styrene content of the high-frequency dielectric heating adhesive affects both injection moldability and adhesion to adherends containing styrene-based resins. If the styrene content of the high-frequency dielectric heating adhesive is too low, it becomes difficult to achieve excellent adhesion to adherends containing styrene-based resins. On the other hand, if the styrene content of the high-frequency dielectric heating adhesive is too high, the fluidity of the high-frequency dielectric heating adhesive decreases, making the high-frequency dielectric heating adhesive less suitable for injection molding. The inventors also discovered that excellent injection moldability can be achieved by setting the upper limit of the complex viscosity of the high-frequency dielectric heating adhesive under specific conditions to 350 Pa·s or less. Furthermore, the present inventors have discovered that by setting the lower limit of the storage modulus of the high-frequency dielectric heating adhesive at 110°C to 300 MPa or higher, excellent adhesion to adherends containing styrene-based resins can be achieved even in high-temperature environments. Based on these findings, the high-frequency dielectric heating adhesive according to this embodiment is believed to have excellent heat resistance. Therefore, even if the adherend contains a thermoplastic resin containing a styrene-based resin with excellent heat resistance, such as polyphenylene ether containing a styrene-based resin, the high-frequency dielectric heating adhesive according to this embodiment has excellent adhesion in high-temperature environments. Furthermore, based on the above findings, the high-frequency dielectric heating adhesive according to this embodiment is believed to have excellent fluidity when heated. Therefore, the high-frequency dielectric heating adhesive according to this embodiment has excellent injection moldability. Based on the above, the present inventors infer that the high-frequency dielectric heating adhesive according to this embodiment has excellent injection moldability compared to conventional high-frequency dielectric heating adhesives, and has excellent adhesion to adherends regardless of environmental conditions, even if the adherend contains a styrene-based resin.Furthermore, the inventors speculate that the high-frequency dielectric heating adhesive according to this embodiment has excellent adhesion to adherends regardless of environmental conditions, and therefore has excellent adhesion to adherends containing thermoplastic resins, including styrene-based resins, even in low-temperature environments below 0°C.

[0024] The materials used in the high-frequency dielectric heating adhesive according to this embodiment will be described below.

[0025] <Thermoplastic Resin (A)> The types of thermoplastic resin (A) include a styrene-based thermoplastic elastomer (a1) and a thermoplastic resin (a2) other than the styrene-based thermoplastic elastomer (a1).

[0026] (Styrenic thermoplastic elastomer (a1)) The styrene-based thermoplastic elastomer (a1) is an elastomer of a copolymer resin containing styrene as a monomer unit. The styrene-based thermoplastic elastomer (a1) may contain one or both of a hydrogenated styrene-based copolymer resin and an unhydrogenated styrene-based copolymer resin. The styrene-based thermoplastic elastomer (a1) may be used alone or in combination of two or more. In this specification, among styrene-based resins, resins that can be classified as styrene-based thermoplastic elastomers are referred to as styrene-based thermoplastic elastomers, and the terms "styrene-based resin" and "styrene-based thermoplastic elastomer" are used to distinguish between them.

[0027] Examples of the styrene-based thermoplastic elastomer (a1) include a styrene-conjugated diene copolymer and a styrene-olefin copolymer. Examples of the styrene-conjugated diene copolymer include an unhydrogenated styrene-conjugated diene copolymer and a hydrogenated styrene-conjugated diene copolymer.

[0028] Specific examples of the unhydrogenated styrene-conjugated diene copolymer include at least one selected from the group consisting of styrene-butadiene copolymer, styrene-butadiene-styrene copolymer, styrene-(butadiene / butylene)-styrene copolymer, styrene-isoprene copolymer, styrene-isoprene-styrene copolymer, and styrene-(ethylene / isoprene)-styrene copolymer, etc. The unhydrogenated styrene-conjugated diene copolymer may be used alone or in combination of two or more.

[0029] Specific examples of the hydrogenated styrene-conjugated diene copolymer include at least one selected from the group consisting of a styrene-(ethylene / propylene)-styrene copolymer and a styrene-(ethylene / butylene)-styrene copolymer. The styrene-(ethylene / propylene)-styrene copolymer is a hydrogenated product of a styrene-isoprene-styrene copolymer. The styrene-(ethylene / butylene)-styrene copolymer is a hydrogenated product of a styrene-butadiene-styrene copolymer. The hydrogenated styrene-conjugated diene copolymer may be used alone or in combination of two or more.

[0030] From the viewpoint of excellent adhesion to adherends containing styrene-based resins regardless of environmental conditions, the styrene-based thermoplastic elastomer (a1) preferably contains a hydrogenated product of a styrene-based copolymer resin. From the same viewpoint, the styrene-based thermoplastic elastomer (a1) more preferably contains styrene-(ethylene / butylene)-styrene. If the styrene-based thermoplastic elastomer (a1) contains, for example, styrene-(ethylene / butylene)-styrene, the heat resistance of the high-frequency dielectric heating adhesive is likely to be improved. Furthermore, if the styrene-based thermoplastic elastomer (a1) contains, for example, styrene-(ethylene / butylene)-styrene, high adhesive strength between the adherend containing a styrene-based resin and the high-frequency dielectric heating adhesive is likely to be obtained, even in high-temperature environments.

[0031] The content of the styrene thermoplastic elastomer (a1) relative to the total thermoplastic resin (A) is not particularly limited, as long as the content of the styrene component relative to the total thermoplastic resin (A) is in the range of 20.0 mass% or more and 45.0 mass% or less. From the viewpoint of excellent injection moldability and excellent adhesion to an adherend containing a styrene resin regardless of environmental conditions, the content of the styrene thermoplastic elastomer (a1) relative to the total thermoplastic resin (A) is, for example, preferably 27.0 vol% or more, more preferably 29.0 vol% or more, even more preferably 31.0 vol% or more, still more preferably 33.0 vol% or more, and even more preferably 35.0 vol% or more. From the same viewpoint, the content of the styrene-based thermoplastic elastomer (a1) is, for example, preferably 75.0 vol% or less, more preferably 71.0 vol% or less, more preferably 69.0 vol% or less, even more preferably 67.0 vol% or less, and even more preferably 65.0 vol% or less, relative to the total thermoplastic resin (A). Here, the content relative to the total thermoplastic resin (A) represents, in the case of a volume basis, the content when the total thermoplastic resin (A) is taken as 100 vol%, and in the case of a mass basis, represents the content when the total thermoplastic resin (A) is taken as 100 mass%.

[0032] The content of the styrene-based thermoplastic elastomer (a1) in the entire high-frequency dielectric heating adhesive is not particularly limited, as long as the content of the styrene component in the entire thermoplastic resin (A) is in the range of 20.0 mass% or more and 45.0 mass% or less. From the viewpoint of excellent injection moldability and excellent adhesion to adherends containing styrene-based resins regardless of environmental conditions, the content of the styrene-based thermoplastic elastomer (a1) in the entire high-frequency dielectric heating adhesive is preferably 15.0 volume% or more and 55.0 volume% or less. From the viewpoint of even better adhesion to adherends containing styrene-based resins regardless of environmental conditions, the content of the styrene-based thermoplastic elastomer (a1) in the entire high-frequency dielectric heating adhesive is more preferably 18.0 volume% or more, and even more preferably 20.0 volume% or more. From the viewpoint of obtaining better injection moldability, the content of the styrene-based thermoplastic elastomer (a1) is more preferably 53.0% by volume or less, and even more preferably 51.0% by volume or less, relative to the entire high-frequency dielectric heating adhesive. Here, the content relative to the entire high-frequency dielectric heating adhesive is, when based on volume, the content when the entire high-frequency dielectric heating adhesive is taken as 100% by volume, and when based on mass, the content when the entire high-frequency dielectric heating adhesive is taken as 100% by mass.

[0033] If the content of the styrene-based thermoplastic elastomer (a1) is 15.0% by volume or more relative to the entire high-frequency dielectric heating adhesive, it becomes easier to obtain a high-frequency dielectric heating adhesive that has excellent adhesion to adherends containing styrene-based resins, regardless of environmental conditions.If the content of the styrene-based thermoplastic elastomer (a1) is 55.0% by volume or less relative to the entire high-frequency dielectric heating adhesive, it becomes easier to obtain excellent injection moldability because an increase in viscosity in the high-shear region is suppressed and fluidity can be easily adjusted to an appropriate range.

[0034] From the viewpoint of easily obtaining superior adhesion to an adherend containing a styrene-based resin regardless of environmental conditions, the content of the styrene component in the styrene-based thermoplastic elastomer (a1) is preferably 15.0 mass% or more, more preferably 20.0 mass% or more, even more preferably 25.0 mass% or more, still more preferably 30.0 mass% or more, even more preferably 40.0 mass% or more, and even more preferably 50.0 mass% or more. From the viewpoint of easily obtaining superior injection moldability, the content of the styrene component in the styrene-based thermoplastic elastomer (a1) is preferably 80.0 mass% or less, more preferably 75.0 mass% or less, and even more preferably 70.0 mass% or less.

[0035] (Thermoplastic resin (a2)) The thermoplastic resin (a2) is a thermoplastic resin other than the styrene-based thermoplastic elastomer (a1). That is, the thermoplastic resin (a2) is a resin different from the styrene-based thermoplastic elastomer (a1), and is not the styrene-based thermoplastic elastomer (a1).

[0036] The thermoplastic resin (a2) is preferably at least one selected from the group consisting of polyolefin resins, styrene resins, polyacetal resins, polycarbonate resins, acrylic resins, polyamide resins, polyimide resins, polyvinyl acetate resins, phenoxy resins, and polyester resins, for example, from the viewpoint of being easily meltable and having a predetermined heat resistance. It is preferable to select a type of resin for the thermoplastic resin (a2) that has high affinity with the material of the adherend. It is also preferable to select a type of resin for the thermoplastic resin (a2) that has high affinity with the styrene thermoplastic elastomer (a1). Furthermore, it is preferable to select a type of resin for the thermoplastic resin (a2) that has excellent fluidity.

[0037] In the high-frequency dielectric heating adhesive according to this embodiment, the thermoplastic resin (a2) is preferably a polyolefin-based resin or a styrene-based resin, and more preferably a polyolefin-based resin. If the thermoplastic resin (a2) is a polyolefin-based resin or a styrene-based resin, the high-frequency dielectric heating adhesive is easily melted when a high-frequency electric field is applied, and the high-frequency dielectric heating adhesive according to this embodiment can be easily bonded to an adherend. When the thermoplastic resin (a2) is a styrene-based resin, the styrene-based resin may be used as the thermoplastic resin (a2) so that the content of the styrene component relative to the total thermoplastic resin (A) satisfies 20.0 mass% or more and 45.0 mass% or less. Furthermore, from the viewpoints of affinity with the styrene-based thermoplastic elastomer (a1), the heat resistance of the high-frequency dielectric heating adhesive, and the fluidity of the high-frequency dielectric heating adhesive, the thermoplastic resin (a2) is preferably a polyolefin-based resin. If the thermoplastic resin (a2) is a polyolefin-based resin, it is easier to obtain a high-frequency dielectric heating adhesive that has excellent injection moldability and excellent adhesion to adherends containing styrene-based resins, even in high-temperature environments.

[0038] In this specification, polyolefin-based resins include polyolefin-based resins having polar moieties and polyolefin-based resins not having 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 not having polar moieties.

[0039] The thermoplastic resin (a2) is preferably a polyolefin resin having a polar moiety, but may also be a polyolefin resin having no polar moiety.

[0040] (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-methyl-1-pentene, etc. The polyolefin resin as the thermoplastic resin (a2) may be a single resin or a combination of two or more resins.

[0041] From the viewpoint of excellent injection moldability and excellent adhesion to adherends containing styrene-based resins regardless of environmental conditions, the thermoplastic resin (a2) preferably contains a polypropylene-based resin. The polypropylene-based resin may be a resin composed of a homopolymer of a propylene monomer, or a copolymer containing a propylene monomer. The copolymer containing a propylene monomer may be a propylene-based random copolymer or a propylene-based block copolymer. The polypropylene-based resin may be a single resin or a combination of two or more resins. If the thermoplastic resin (a2) contains a polypropylene-based resin, excellent compatibility with the styrene-based thermoplastic elastomer (a1) is easily obtained. Furthermore, if the thermoplastic resin (a2) contains a polypropylene-based resin, an excellent balance between fluidity and heat resistance is easily obtained.

[0042] [Polyolefin Resin Having 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. Furthermore, it is preferable that the high-frequency dielectric heating adhesive contains a polyolefin resin having polar moieties as the thermoplastic resin (a2), as this tends to improve the dielectric properties and increase the adhesive strength to the adherend. The polyolefin thermoplastic resin having polar moieties may be a copolymer of an olefin monomer and a monomer having a polar moiety. Furthermore, the polyolefin thermoplastic resin having polar moieties may be a resin obtained by introducing polar moieties into an olefin polymer obtained by polymerization of an olefin monomer through modification such as an addition reaction.

[0043] The type of olefin monomer constituting the polyolefin resin having a polar moiety is not particularly limited. Examples of olefin monomers 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. From the viewpoint of obtaining excellent mechanical strength and stable adhesive properties, the olefin monomer is preferably at least one of ethylene and propylene. The olefin-derived structural unit in the polyolefin resin having a polar moiety is preferably a structural unit derived from ethylene or propylene.

[0044] 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.

[0045] 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 thermoplastic resin (e.g., 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.

[0046] Examples of unsaturated carboxylic acids include acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, and citraconic acid.

[0047] Examples of the acid anhydrides of unsaturated carboxylic acids include maleic anhydride, itaconic anhydride, and citraconic anhydride.

[0048] Examples of esters of unsaturated carboxylic acids include 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.

[0049] [Maleic Anhydride-Modified Polyolefin] The polyolefin resin as the thermoplastic resin (a2) preferably has an acid anhydride structure as the acid-modified structure. The acid anhydride structure is preferably a structure introduced when the polyolefin resin is modified with maleic anhydride.

[0050] The olefin-derived structural unit in the maleic anhydride-modified polyolefin is preferably a structural unit derived from ethylene or propylene. That is, the maleic anhydride-modified polyolefin is preferably a maleic anhydride-modified polyethylene resin or a maleic anhydride-modified polypropylene resin. Furthermore, from the viewpoints of excellent injection moldability and excellent adhesion to adherends containing styrene-based resins regardless of environmental conditions, the maleic anhydride-modified polyolefin is preferably a maleic anhydride-modified polypropylene resin.

[0051] From the viewpoint of excellent injection moldability and excellent adhesion to adherends containing styrene-based resins regardless of environmental conditions, the content of thermoplastic resin (a2) is preferably 25.0 vol% or more and 65.0 vol% or less, based on the entire high-frequency dielectric heating adhesive. From the viewpoint of obtaining even better injection moldability, the content of thermoplastic resin (a2) is more preferably 28.0 vol% or more, even more preferably 30.0 vol% or more, even more preferably 33.0 vol% or more, and even more preferably 35.0 vol% or more, based on the entire high-frequency dielectric heating adhesive. From the viewpoint of excellent adhesion to adherends containing styrene-based resins regardless of environmental conditions, the content of thermoplastic resin (a2) is more preferably 60.0 vol% or less, even more preferably 55.0 vol% or less, based on the entire high-frequency dielectric heating adhesive.

[0052] The content (volume content) of the thermoplastic resin (A) in the high-frequency dielectric heating adhesive is preferably 60.0% by volume or more, more preferably 65.0% by volume or more, even more preferably 70.0% by volume or more, even more preferably 75% by volume or more, and even more preferably 78% by volume or more. The content (volume content) of the thermoplastic resin (A) in the high-frequency dielectric heating adhesive is preferably 98.0% by volume or less, more preferably 97.0% by volume or less, even more preferably 96.0% by volume or less, even more preferably 94.0% by volume or less, and even more preferably 92.0% by volume or less.

[0053] <Dielectric filler (B)> The dielectric filler (B), which is a preferred material as a dielectric material, will be described. 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 is reversed at high frequencies. The dielectric filler (B) is preferably a filler that generates heat when a high-frequency electric field in a frequency range of 3 MHz or more and 300 MHz or less is applied. The dielectric filler (B) is preferably a filler that generates heat when a high-frequency electric field in a frequency range of 3 MHz or more and 300 MHz or less is applied, for example, at a frequency of 13.56 MHz, 27.12 MHz, or 40.68 MHz.

[0054] 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.

[0055] From the viewpoint of obtaining higher heat generation properties, the dielectric filler (B) is preferably at least one selected from the group consisting of zinc oxide, silicon carbide, titanium oxide, and barium titanate, more preferably at least one selected from the group consisting of zinc oxide, silicon carbide, and titanium oxide, and even more preferably at least one selected from the group consisting of zinc oxide and titanium oxide.

[0056] Among the dielectric fillers listed above, zinc oxide 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. For this reason, zinc oxide is more preferred as the dielectric filler (B). By using zinc oxide as the dielectric filler (B), a high-frequency dielectric heating adhesive with low transmittance and no design issues can be obtained. Zinc oxide is not too hard among ceramics, making it less likely to damage the manufacturing equipment for high-frequency dielectric heating adhesives. Because zinc oxide is an inactive oxide, it causes less damage to thermoplastic resins when blended with them. Furthermore, titanium oxide as the dielectric filler (B) is preferably at least one of anatase titanium oxide and rutile titanium oxide, and anatase titanium oxide is more preferred from the viewpoint of its excellent dielectric properties.

[0057] The shape of the dielectric filler (B) is not particularly limited, and various shapes can be adopted.

[0058] The content (volume content) of the dielectric filler (B) in the high-frequency dielectric heating adhesive is preferably 2.0% by volume or more, more preferably 3.0% by volume or more, even more preferably 4.0% by volume or more, even more preferably 6.0% by volume or more, and even more preferably 8.0% by volume or more. The content (volume content) of the dielectric filler (B) in the high-frequency dielectric heating adhesive is preferably 40.0% by volume or less, more preferably 35.0% by volume or less, even more preferably 30.0% by volume or less, even more preferably 25.0% by volume or less, and even more preferably 22% by volume or less.

[0059] When the volume content of the dielectric filler (B) in the high-frequency dielectric heating adhesive is 2.0% by volume or more, heat generation is improved and it is easy to firmly bond the high-frequency dielectric heating adhesive to the adherend. When the volume content of the dielectric filler (B) in the high-frequency dielectric heating adhesive is 40.0% by volume or less, a decrease in adhesive strength can be prevented, and as a result, use of this adhesive can prevent a decrease in adhesive strength. Furthermore, when the high-frequency dielectric heating adhesive according to this embodiment is in the form of an adhesive sheet, when the volume content of the dielectric filler (B) in the adhesive sheet is 40.0% by volume or less, flexibility as a sheet can be easily obtained and a decrease in toughness can be easily prevented, making it easy to process the high-frequency dielectric heating adhesive sheet into the desired shape in a subsequent process.

[0060] The volume average particle diameter of the dielectric filler (B) is preferably 0.1 μm or more, more preferably 1.0 μm or more, and even more preferably 2.0 μm or more. The volume average particle diameter of the dielectric filler (B) is preferably 25.0 μm or less, more preferably 20.0 μm or less, even more preferably 15.0 μm or less, and particularly preferably 10.0 μm or less.

[0061] When the volume average particle diameter of the dielectric filler (B) is 0.1 μm or more, the high-frequency dielectric heating adhesive exhibits high heat-generating performance when a high-frequency electric field is applied, and can be firmly bonded to an adherend in a short time. When the volume average particle diameter of the dielectric filler (B) is 25 μm or less, the high-frequency dielectric heating adhesive exhibits high heat-generating performance when a high-frequency electric field is applied, and can be firmly bonded to an adherend in a short time. Furthermore, when the high-frequency dielectric heating adhesive according to this embodiment is an adhesive sheet, a decrease in the strength of the high-frequency dielectric heating adhesive sheet can be prevented by having the volume average particle diameter of the dielectric filler (B) be 25 μm or less.

[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 8819-2:2019.

[0063] <Additives> The high-frequency dielectric heating adhesive according to this embodiment may or may not contain additives, as long as the adhesive does not impair short-term adhesion.

[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, and an inorganic filler. 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 high-frequency dielectric heating adhesives. Examples of tackifiers include rosin derivatives, polyterpene resins, aromatic-modified terpene resins, hydrogenated aromatic-modified terpene resins, terpene-phenolic 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 paraffinic 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 usually 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. Also, 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 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, metals, etc. For example, the high-frequency dielectric heating adhesive according to this embodiment preferably does not contain 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 according to this embodiment contains a conductive substance, the content of the conductive substance in the adhesive is preferably, independently, 7% by mass or less, more preferably 6% by mass or less, even more preferably 5% by mass or less, even more preferably 1% by mass or less, and even more preferably 0.1% by mass or less, based on the total amount of the adhesive. It is particularly preferable that the content of the conductive substance in the adhesive is 0% by mass. If the content of the conductive substance in the adhesive is 7% by mass or less, it becomes easier to prevent problems such as electrical breakdown during dielectric heating treatment, resulting in carbonization of the bonded joint and the adherend.

[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] (Styrene Component Content) In the high-frequency dielectric heating adhesive according to this embodiment, the styrene component content relative to the entire thermoplastic resin (A) is 20.0% by mass or more and 45.0% by mass or less. The styrene component content relative to the entire thermoplastic resin (A) is preferably 22.0% by mass or more, more preferably 24.0% by mass or more, and even more preferably 30.0% by mass or more. The styrene component content relative to the entire thermoplastic resin (A) is preferably 44.0% by mass or less, more preferably 43.0% by mass or less, and even more preferably 42.0% by mass or less. When the styrene component content relative to the entire thermoplastic resin (A) is 20.0% by mass or more, excellent adhesion to an adherend containing a styrene-based resin can be obtained regardless of environmental conditions. For example, excellent adhesion to an adherend containing a styrene-based resin can be obtained even in a high-temperature environment such as 110°C. Furthermore, if the content of the styrene component relative to the entire thermoplastic resin (A) is 45.0 mass% or less, the fluidity of the high-frequency dielectric heating adhesive will be in an appropriate range, and excellent injection moldability will be obtained.

[0073] (Storage Modulus) In the high-frequency dielectric heating adhesive according to this embodiment, the storage modulus in a 110°C environment is 300 MPa or more. The storage modulus in a 110°C environment is more preferably 310 MPa or more, even more preferably 320 MPa or more, even more preferably 330 MPa or more, and even more preferably 340 MPa or more. The upper limit of the storage modulus in a 110°C environment is not particularly limited, and may be, for example, 1500 MPa or less, 1000 MPa or less, or 800 MPa or less. If the storage modulus in a 110°C environment is 300 MPa or more, excellent adhesion to an adherend containing a styrene-based resin can be obtained regardless of the environmental conditions. For example, excellent adhesion to an adherend containing a styrene-based resin can be obtained even in a high-temperature environment such as 110°C.

[0074] (Complex Viscosity) In the high-frequency dielectric heating adhesive according to this embodiment, the complex viscosity at a 220°C environment and a shear rate of 600 rad / s is 350 Pa·s or less. The complex viscosity at a 220°C environment and a shear rate of 600 rad / s is preferably 340 Pa·s or less, more preferably 330 Pa·s or less, even more preferably 320 Pa·s or less, even more preferably 310 Pa·s or less, and even more preferably 300 Pa·s or less. If the complex viscosity at a 220°C environment and a shear rate of 600 rad / s is 350 Pa·s or less, the fluidity of the high-frequency dielectric heating adhesive falls within an appropriate range, resulting in excellent injection moldability. The lower limit of the complex viscosity at a 220°C environment and a shear rate of 600 rad / s is not particularly limited, and may be, for example, 150 Pa·s or more. Furthermore, if the complex viscosity at a shear rate of 600 rad / s in an environment of 220°C is 350 Pa·s or less, excellent injection moldability can be obtained, and therefore even if the thickness of the high-frequency dielectric heating adhesive is thin, a high-frequency dielectric heating adhesive can be obtained by injection molding.

[0075] (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 preferably has a dielectric property (tan δ / ε'r) of 0.005 or more. (Tan δ is the dielectric loss tangent at 23°C and a frequency of 40.68 MHz, and ε'r is the relative dielectric constant at 23°C and a frequency of 40.68 MHz.)

[0076] 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 a dielectric heating process, making it easier to firmly bond the high-frequency dielectric heating adhesive to the adherend in a short period of time.

[0077] The dielectric properties of the high-frequency dielectric heating adhesive according to this embodiment are preferably 0.0055 or more, and more preferably 0.006 or more. If the high-frequency dielectric heating adhesive according to this embodiment has a dielectric property of 0.006 or more, the high-frequency dielectric heating adhesive will be more likely to generate heat when subjected to a dielectric heating treatment, making it easier to firmly bond the high-frequency dielectric heating adhesive to the adherend in a short period of time.

[0078] 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 properties of the high-frequency dielectric heating adhesive are 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.

[0079] The dielectric property (tan δ / ε'r) is the value obtained by dividing the dielectric loss tangent (tan δ) measured using an impedance material apparatus, etc., by the relative dielectric constant (ε'r) measured using an impedance material apparatus, etc. The dielectric loss tangent (tan δ) and relative dielectric constant (ε'r), which are the dielectric properties of a high-frequency dielectric heating adhesive, can be measured simply and accurately using an impedance material analyzer.

[0080] 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 non-sheet-formed high-frequency dielectric heating adhesives, such as pellet-shaped ones, the measurement sheet is obtained by sheeting them 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.

[0081] (Melt Volume Rate) In the high-frequency dielectric heating adhesive according to this embodiment, the melt volume rate (hereinafter sometimes referred to as MVR) of the high-frequency dielectric heating adhesive is 25 cm ３ / 10 min or more is preferable, and 35 cm ３ / 10 min or more is more preferable, ３ It is more preferable that the MVR of the high frequency dielectric heating adhesive is 25 cm / 10 min or more. ３ If the MVR is 100 / min or more, the fluidity of the high-frequency dielectric heating adhesive falls within a suitable range, and therefore excellent injection moldability is likely to be obtained. ３ / 10 min or less, 200 cm ３ / 10 min or less, 150 cm ３ / 10 min or less, 120 cm ３ In this specification, the term "min" in the units is an abbreviation for "minutes."

[0082] In the high-frequency dielectric heating adhesive according to this embodiment, MVR (cm ３ / 10 min) is a value measured using a flow tester with a measurement load of 5 kg and a measurement temperature of 240°C. Specifically, the MVR of a high-frequency dielectric heating adhesive can be measured by the method described in the Examples section below.

[0083] <Shape of High-Frequency Dielectric Heating Adhesive> The shape of the high-frequency dielectric heating adhesive according to this embodiment is not particularly limited. The high-frequency dielectric heating adhesive according to this embodiment may be, for example, a molded adhesive formed into a desired shape by injection molding or the like, or a sheet-like adhesive obtained by extrusion molding or the like. In this embodiment, the molded body and the sheet have different shapes. A sheet typically refers to a long strip or sheet-like shape with a thickness of 1 mm or less, 2 mm or less, or 5 mm or less. A molded body refers to a shape obtained by molding a material containing each component of the high-frequency dielectric heating adhesive, and refers to various shapes other than a sheet.

[0084] The high-frequency dielectric heating adhesive according to this embodiment is preferably in sheet form. That is, the high-frequency dielectric heating adhesive according to this embodiment is preferably a high-frequency dielectric heating adhesive sheet (sometimes referred to as an 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.

[0085] The high-frequency dielectric heating adhesive according to this embodiment may have the shape of a frame-shaped sheet (frame-shaped adhesive sheet) including a frame portion and an opening penetrating from one opposing surface to the other. The shape of the opening is not particularly limited. When the adhesive sheet is frame-shaped, the frame-shaped adhesive sheet may have one opening or two or more openings. The frame-shaped sheet may have a cutout in a portion of the frame portion. In this case, the opening may be shaped so that a portion of the frame portion is connected to the outside of the frame portion. That is, in a plan view of the frame-shaped sheet, the frame portion may have an open shape (for example, a discontinuous shape of the frame portion, such as a C-shape or a U-shape). The frame-shaped sheet may not have a cutout in the frame portion. In this case, the opening may be shaped so that the periphery of the opening is surrounded by the frame portion (for example, a continuous shape of the frame portion, such as an O-shape). That is, in a plan view of the frame-shaped sheet, the frame portion may have a closed shape. When the frame-shaped sheet has two or more openings, the openings may be a combination of openings of the same shape or a combination of openings of different shapes when viewed from above. The high-frequency dielectric heating adhesive according to this embodiment may be a sheet without any openings. Furthermore, the high-frequency dielectric heating adhesive according to this embodiment can be molded into an adhesive sheet of the desired shape by molding methods such as extrusion molding and injection molding. The high-frequency dielectric heating adhesive according to this embodiment is preferably an injection-molded product because of its excellent injection moldability. If the high-frequency dielectric heating adhesive according to this embodiment is an injection-molded product, it is easy to realize a high-frequency dielectric heating adhesive of a complex shape. If the high-frequency dielectric heating adhesive according to this embodiment is an injection-molded product, the high-frequency dielectric heating adhesive may be in the form of a sheet or a molded product.

[0086] 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. It is preferable that the high-frequency dielectric heating adhesive sheet consists of only a single adhesive layer. This allows the high-frequency dielectric heating adhesive sheet to be thin and the high-frequency dielectric heating adhesive sheet to be easily formed.

[0087] 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.

[0088] The high-frequency dielectric heating adhesive according to this embodiment is not limited to an adhesive sheet for high-frequency dielectric heating consisting of only one adhesive layer, and may be any of the adhesives shown in Figures 1A, 1B, and 1C.

[0089] The high frequency dielectric heating adhesive 1A shown in FIG. 1A is an adhesive sheet consisting of only a single adhesive layer 10.

[0090] 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, acrylonitrile-butadiene-styrene copolymer 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. The dielectric filler (B) in the adhesive layer 10 and the dielectric filler in the substrate 30 may be the same or different.

[0091] 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 formed from a pressure-sensitive adhesive.

[0092] When the high-frequency dielectric heating adhesive according to this embodiment is an adhesive sheet consisting of only one adhesive layer, the thickness of the adhesive sheet according to 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. If the adhesive sheet is 5 μm or more thick, the heat generation properties of the adhesive sheet in contact with the adherend when a high-frequency electric field is applied are improved, making it easier to firmly bond the adhesive sheet and the adherend in a short period of time. Furthermore, when bonding to the adherend, the adhesive sheet easily conforms to the unevenness of the adherend, making it easier to develop adhesive strength.

[0093] When the adhesive sheet has a multilayer structure made up 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 multilayer sheet, if the thickness of the adhesive layer is 5 μm or more, the adhesive layer will easily follow the irregularities of the adherend when adhering to the adherend, and adhesive strength will be easily exhibited.

[0094] 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. For this reason, the adhesive sheet preferably has a thickness within a range that does not pose any 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.

[0095] 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.

[0096] Furthermore, the thickness of the adhesive sheet used as a high-frequency dielectric heating adhesive can be appropriately controlled. This allows the adhesive sheet to be applied to the roll-to-roll method, and the adhesive sheet can be processed into any area and shape by punching or other processes to match the adhesive area with the adherend and the shape of the adherend. Therefore, adhesive sheets used as high-frequency dielectric heating adhesives have great advantages from the viewpoint of the manufacturing process.

[0097] The high-frequency dielectric heating adhesive according to this embodiment is preferably used by applying a high-frequency electric field in a frequency range from short waves to ultra-short waves. When a high-frequency electric field in this frequency range is applied, the heatable depth is deep, improving heat generation during high-frequency application. Therefore, even if the high-frequency dielectric heating adhesive is thick, it is easy to firmly bond the adhesive sheet to the adherend in a short time.

[0098] <Method for Manufacturing High-Frequency Dielectric Heating Adhesive> The high-frequency dielectric heating adhesive according to this embodiment can be manufactured, for example, by mixing the above-described components. When the high-frequency dielectric heating adhesive according to this embodiment is an adhesive sheet, for example, the above-described components are premixed and kneaded using a known kneading device such as an extruder or a heated roll, and the adhesive can be manufactured by a known molding method such as extrusion molding, calendar molding, injection molding, or casting molding. When the high-frequency dielectric heating adhesive according to this embodiment is a molded body, for example, the material obtained by premixing the above-described components can be manufactured by a known molding method such as injection molding or compression molding. Furthermore, when the high-frequency dielectric heating adhesive according to this embodiment is a frame-shaped sheet, the frame-shaped sheet can be manufactured by forming openings in the sheet-shaped high-frequency dielectric heating adhesive obtained by the above-described adhesive sheet molding method, for example, by subjecting it to a known punching process. Alternatively, the frame-shaped sheet can be manufactured by using a mold with a shape that allows the desired openings to be obtained in the above-described adhesive sheet molding method. The high-frequency dielectric heating adhesive according to this embodiment has excellent injection moldability, so it is preferably manufactured by injection molding. If the high-frequency dielectric heating adhesive according to this embodiment is manufactured by injection molding, it can be easily manufactured even if the high-frequency dielectric heating adhesive has a complex shape. For example, even if the desired high-frequency dielectric heating adhesive is the frame-shaped sheet described above, the high-frequency dielectric heating adhesive for the frame-shaped sheet can be easily manufactured by injection molding.

[0099] High frequency dielectric heating adhesives have superior water resistance and moisture resistance compared to general pressure sensitive adhesives.

[0100] 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 problem of the entire adherend being damaged when the adhesive is bonded to the adherend.

[0101] [Adherend] The material of the adherend is not particularly limited, and may be any of organic materials, metal materials, and inorganic materials, or a composite material thereof.

[0102] The material of the adherend is preferably an organic material. Examples of organic materials that can be used as 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, polycarbonate resin, polyamide resin (e.g., nylon 6 and nylon 66), polyester resin (e.g., polyethylene terephthalate and polybutylene terephthalate), polyacetal resin, polymethyl methacrylate resin, and polystyrene resin. Examples of rubber materials include styrene-butadiene rubber, ethylene propylene rubber, and silicone rubber. The adherend may also be an organic foam material. Other examples of organic materials that can be used as the adherend include highly heat-resistant organic materials such as super engineering plastics. The high-frequency dielectric heating adhesive according to this embodiment has excellent heat resistance. In this respect, it is also preferable that the adherend include a highly heat-resistant organic material.

[0103] When the material of the adherend is a thermoplastic resin, the thermoplastic resin contained in the adherend and the thermoplastic resin (A) contained in the high-frequency dielectric heating adhesive may be different resins, in which case bonding is facilitated without damaging the shape of the adherend.

[0104] Furthermore, when the material of the adherend is a thermoplastic resin, from the viewpoint of adhesiveness, the main composition of the thermoplastic resin contained in the adherend may be the same as the main composition of the thermoplastic resin (A) contained in the high-frequency dielectric heating adhesive.

[0105] In this specification, the "main composition of the thermoplastic resin" refers to, for example, when the thermoplastic resin is a polymer, the repeating unit contained in the polymer that is the most abundant repeating unit in the polymer. When the thermoplastic resin is a polymer derived from a single monomer, the repeating unit derived from that monomer unit is the "main composition of the thermoplastic resin." When the thermoplastic resin is a copolymer, the repeating unit contained in the polymer that is the most abundant repeating unit is the "main composition of the thermoplastic resin." When the thermoplastic resin is a copolymer, the "main composition of the thermoplastic resin" in the copolymer is a repeating unit contained in an amount of 30% by mass or more, in one embodiment, a repeating unit contained in an amount of more than 30% by mass, in another embodiment, a repeating unit contained in an amount of 40% by mass or more, and in yet another embodiment, a repeating unit contained in an amount of 50% by mass or more. Furthermore, when the thermoplastic resin is a copolymer, the repeating unit contained in the most abundant amount may be two or more types.

[0106] Examples of inorganic materials used as the adherend include glass, cement, ceramic, and metal materials. The adherend may also be a fiber-reinforced resin, which is a composite material of fibers and the aforementioned plastic materials. The plastic material in this fiber-reinforced resin is at least one selected from the group consisting of polypropylene resin, polyethylene resin, polyurethane resin, acrylonitrile-butadiene-styrene copolymer resin, polycarbonate resin, polyamide resin (e.g., nylon 6 and nylon 66), polyester resin (e.g., polyethylene terephthalate and polybutylene terephthalate resin), polyacetal resin, polymethyl methacrylate resin, epoxy resin, and polystyrene resin. Examples of fibers in the fiber-reinforced resin include glass fiber, Kevlar® fiber, and carbon fiber.

[0107] The adherend preferably has low electrical conductivity.

[0108] When a plurality of adherends are bonded together using the adhesive for high-frequency dielectric heating according to this embodiment, the adherends may be made of the same material or different materials.

[0109] 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 shape of a sheet, plate, or block. When multiple adherends are to be bonded together, the shapes and dimensions of the adherends may be the same or different.

[0110] Since the high-frequency dielectric heating adhesive according to this embodiment contains a styrene-based thermoplastic elastomer (a1), the adherend is preferably an adherend containing a styrene-based resin. A styrene-based resin is a polymer containing styrenes as monomer units. An adherend containing a styrene-based resin may contain a styrene-based resin. The resin used for an adherend containing a styrene-based resin may be a styrene-based resin alone, a polymer alloy containing a styrene-based resin, or a combination of a styrene-based resin and another resin. The high-frequency dielectric heating adhesive according to this embodiment provides excellent adhesion to an adherend containing a styrene-based resin regardless of environmental conditions. Therefore, as long as the adherend contains a styrene-based resin, the adhesive exhibits excellent adhesion to an adherend containing a styrene-based resin even in high-temperature environments. The adherend containing a styrene-based resin is preferably an adherend containing, for example, a resin with excellent heat resistance that is mixed with a styrene-based resin. Specifically, an adherend containing a modified polyphenylene ether, which is a polyphenylene ether mixed with a styrene-based resin, is also preferably used.

[0111] [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, 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 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. The high-frequency dielectric heating adhesive according to this embodiment provides excellent adhesion to adherends containing styrene-based resins regardless of environmental conditions. Therefore, in one aspect, the structure according to this embodiment includes the high-frequency dielectric heating adhesive according to this embodiment and an adherend containing a styrene-based resin, and the adherend is preferably bonded with 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.

[0112] 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 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 the length direction. The structure 100 is disposed in a position where the longitudinal centers of the first adherend 110, the high-frequency dielectric heating adhesive 1A, and the second adherend 120 are aligned. In the structure 100 shown in FIG. 2, the first adherend 110 and the second adherend 120 each preferably contain a styrene-based resin. The high-frequency dielectric heating adhesive 1A is the high-frequency dielectric heating adhesive according to this embodiment. When the first adherend 110 and the second adherend 120 each contain a styrene-based resin, the styrene-based resins contained in the first adherend 110 and the second adherend 120 may be different from each other or the same. When the first adherend 110 and the second adherend 120 contain a styrene-based resin, the styrene-based resin contained in the first adherend 110 and the second adherend 120 may be only a styrene-based resin, a polymer alloy mixed with a styrene-based resin, or a combination of a styrene-based resin and another resin. The styrene-based resin contained in the first adherend 110 and the second adherend 120 is preferably the modified polyphenylene ether described above. As described above, the modified polyphenylene ether is a polyphenylene ether mixed with a styrene-based resin.

[0113] 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 Fig. 2. In the structure according to this embodiment, the shape, size, number, etc. of the adherends are not limited to those shown in Fig. 2. The structure according to this embodiment is not limited to the structure shown in Fig. 2 in which two adherends are stacked with the high-frequency dielectric heating adhesive interposed therebetween.

[0114] [Bonding method] Next, as an example of a bonding method for bonding an adherend using the high-frequency dielectric heating adhesive according to this embodiment, a method for manufacturing a structure by bonding the high-frequency dielectric heating adhesive according to this embodiment to an adherend will be described. The method for manufacturing a structure when manufacturing a structure by bonding the high-frequency dielectric heating adhesive according to this embodiment to an adherend includes, for example, the following steps.

[0115] When a structure is produced by bonding one or more adherends to the high-frequency dielectric heating adhesive according to this embodiment, the method for producing 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, 1 MHz or more and 300 MHz or less.

[0116] When a structure is produced by bonding two or more adherends to the high-frequency dielectric heating adhesive according to this embodiment, the method for producing 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, too, the frequency of the applied high-frequency electric field is, for example, 1 MHz or more and 300 MHz or less.

[0117] 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. Applying a high-frequency electric field while applying pressure with the electrodes in this manner makes it easier to manufacture a structure in a shorter time. In this specification, the term "dielectric heating device" may also be referred to as "high-frequency dielectric heating device."

[0118] 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.

[0119] Below, as an example of a method for manufacturing a structure according to this embodiment, an embodiment in which two or more adherends are bonded using the high-frequency dielectric heating adhesive according to this embodiment will be described, but the present invention is not limited to this embodiment.

[0120] The bonding method according to one aspect of this embodiment includes the following steps P1 and P2.

[0121] Step P1 is a step of placing the high-frequency dielectric heating adhesive according to this embodiment between two or more adherends. When producing a laminate 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.

[0122] It is preferable to sandwich the high-frequency dielectric heating adhesive between the adherends so that they can be bonded together. The high-frequency dielectric heating adhesive may be sandwiched between a portion of the adherends, between multiple portions of the adherends, or across 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 bonding surface between the adherends. Another example of sandwiching the high-frequency dielectric heating adhesive between a portion of the adherends is to arrange the high-frequency dielectric heating adhesive in a frame shape along the periphery of the bonding surface between the adherends and sandwich it between the adherends. By arranging the high-frequency dielectric heating adhesive in this frame shape, adhesive strength between the adherends can be obtained and the weight of the structure can be reduced compared to when the high-frequency dielectric heating adhesive is arranged over the entire bonding surface. Furthermore, according to one embodiment in which the 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 the high-frequency dielectric heating adhesive is placed over the entire bonding surface.

[0123] Process P2 is a process for bonding two or more adherends by applying a high-frequency electric field to the high-frequency dielectric heating adhesive placed between the adherends in process P1. In one embodiment, the frequency of the applied high-frequency electric field is 1 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.

[0124] <Dielectric Heating Device> FIG. 3 is 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. 3 includes a first high-frequency electric field application electrode 51, a second high-frequency electric field application electrode 52, and a high-frequency power supply 53. The first high-frequency electric field application electrode 51 and the second high-frequency electric field application electrode 52 are arranged opposite each other. The first high-frequency electric field application electrode 51 and the second high-frequency electric field application electrode 52 each have a press mechanism. The press mechanism for the electrodes (first high-frequency electric field application electrode 51 and second high-frequency electric field application electrode 52) of the dielectric heating device 50 can pressurize the first adherend 110, the high-frequency dielectric heating adhesive 1A, and the second adherend 120 between the first high-frequency electric field application electrode 51 and the second high-frequency electric field application electrode 52. In other words, 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 arranged between the electrodes.

[0125] When the first high-frequency electric field application electrode 51 and the second high-frequency electric field application electrode 52 form a pair of parallel plate electrodes, this type of electrode arrangement is sometimes referred to as 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.

[0126] A high-frequency power supply 53 is connected to each of the first high-frequency electric field application electrode 51 and the second high-frequency electric field application electrode 52 to apply a high-frequency electric field having a frequency of, for example, about 13.56 MHz, about 27.12 MHz, or about 40.68 MHz. As shown in FIG. 3 , 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 the first high-frequency electric field application electrode 51 and the second high-frequency electric field application electrode 52. Note that two or more adherends may be bonded together without pressure, for example, by the weight of the high-frequency dielectric heating adhesive and the adherends alone.

[0127] 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, causing the thermoplastic resin component in the high-frequency dielectric heating adhesive 1A to melt, and the first adherend 110 and the second adherend 120 can be firmly bonded together even in a short treatment time.

[0128] 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 dielectric filler dispersed in the adhesive component of the high-frequency dielectric heating adhesive 1A absorbs the 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 in a short treatment time.

[0129] The electrodes of the dielectric heating device 50 (the first high-frequency electric field application electrode 51 and the second high-frequency electric field application electrode 52) have a press mechanism, so the dielectric heating device 50 also functions as a press device. Therefore, the first adherend 110 and the second adherend 120 can be more firmly bonded together by the compression direction pressure applied by the first high-frequency electric field application electrode 51 and the second high-frequency electric field application electrode 52 and the heating and melting of the high-frequency dielectric heating adhesive 1A. Note that, although the method for manufacturing a structure has been described using an example in which the structure 100 shown in FIG. 3 is manufactured, the present invention is not limited to this example.

[0130] <High Frequency Dielectric Heating Conditions> The high frequency dielectric heating conditions can be changed as appropriate, but the following conditions are preferred.

[0131] The output of the high-frequency electric field is preferably 1 W or more, more preferably 3 W or more, even more preferably 5 W or more, and even more preferably 10 W or more. The output of the high-frequency electric field is preferably 50,000 W or less, more preferably 10,000 W or less, even more preferably 5,000 W or less, even more preferably 1,000 W or less, and even more preferably 100 W or less. If the output of the high-frequency electric field is 1 W or more, the problem of the temperature not rising easily during the dielectric heating treatment can be prevented, making it easier to obtain good adhesive strength. If the output of the high-frequency electric field is 50,000 W or less, it is easier to prevent the problem of temperature control being difficult during the dielectric heating treatment. The output of the high-frequency electric field indicates the amount of energy transmitted to the object.

[0132] 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 even more preferably 60 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 treatment can be prevented, and therefore good adhesive strength can be easily obtained. If the application time of the high-frequency electric field is 300 seconds or less, problems such as a decrease in the manufacturing efficiency of the structure, an increase in manufacturing costs, and thermal deterioration of the adherend can be easily prevented.

[0133] The frequency of the applied high-frequency electric field is 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 lower, more preferably 100 MHz or lower, even more preferably 80 MHz or lower, and even more preferably 50 MHz or lower. Specifically, the industrial frequency bands of 13.56 MHz, 27.12 MHz, or 40.68 MHz assigned by the International Telecommunication Union are also used in the high-frequency dielectric heating manufacturing method and bonding method of this embodiment. The frequency of the applied high-frequency electric field indicates the manner (speed) of energy transmission.

[0134] When a high-frequency electric field is applied while pressure is being applied, the initial setting value of the pressure applied to the high-frequency dielectric heating adhesive is preferably 1 kPa or more, more preferably 5 kPa or more, even more preferably 10 kPa or more, even more preferably 30 kPa or more, and even more preferably 50 kPa or more. When a high-frequency electric field is applied while pressure is being applied, the initial setting value of the pressure applied to the high-frequency dielectric heating adhesive is preferably 10 MPa or less, more preferably 5 MPa or less, even more preferably 1 MPa or less, and even more preferably 750 kPa or less. Here, the area used as the basis for the initial setting value of the pressure applied to the high-frequency dielectric heating adhesive is the smallest area among the areas of the electrode and the adherend when viewed in plan.

[0135] [Modifications of the Embodiments] The present invention is not limited to the above-described embodiments, and may include modifications and improvements within the scope of achieving the object of the present invention.

[0136] 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.

[0137] 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.

[0138] [Preparation of High-Frequency Dielectric Heating Adhesive] The high-frequency dielectric heating adhesive of each example was prepared according to the following procedure.

[0139] Examples 1 to 4 and Comparative Examples 1 to 8 As materials for preparing high-frequency dielectric heating adhesives, thermoplastic resin (A) and dielectric filler (B) were weighed out in the volumetric proportions shown in Table 1. The styrene-based thermoplastic elastomer (a1) in the thermoplastic resin (A) and the thermoplastic resin (a2) other than the styrene-based thermoplastic elastomer (a1) in the thermoplastic resin (A) were weighed out so that the styrene component content relative to the total of the styrene-based thermoplastic elastomer (a1) and the thermoplastic resin (a2) was the proportion shown in Table 1. In Table 1, the styrene-based thermoplastic elastomer (a1) is represented as TPS (a1) and the thermoplastic resin (a2) is represented as TP (a2). Furthermore, in Table 1, the styrene component content is represented as the St component content.

[0140] Next, the thermoplastic resin (A) and the dielectric filler (B) were premixed. The premixed material of the styrene-based thermoplastic elastomer (a1), the thermoplastic resin (a2), and the dielectric filler (B) was fed into the hopper of a 30 mmφ twin-screw extruder, the cylinder and the die were heated to a predetermined temperature, and the premixed material was melt-kneaded. After cooling the melt-kneaded material, the material was cut to produce granular pellets.

[0141] Next, the produced granular pellets were dried at 80°C for 6 hours, and then injection molded using an injection molding machine at a predetermined cylinder temperature, a predetermined injection speed, a predetermined mold temperature, and a predetermined holding pressure to produce sheet-shaped high-frequency dielectric heating adhesives (high-frequency dielectric heating adhesive sheets) having a thickness of 400 μm and the shape shown in FIG. 4 for Examples 1 to 4 and Comparative Examples 1 to 8.

[0142] FIG. 4 shows a schematic plan view of the high-frequency dielectric heating adhesive sheet prepared in each example. The high-frequency dielectric heating adhesive sheet AS shown in FIG. 4 is a frame-shaped high-frequency dielectric heating adhesive sheet AS formed into a hollow rectangle and equipped with a frame portion Fr and an opening Op. The frame-shaped high-frequency dielectric heating adhesive sheet AS has a first high-frequency dielectric heating adhesive sheet surface AS1 and a second high-frequency dielectric heating adhesive sheet surface AS2, which are opposing surfaces. The second high-frequency dielectric heating adhesive sheet surface AS2 is the surface opposite the first high-frequency dielectric heating adhesive sheet surface AS1. The opening Op is formed by penetrating the first high-frequency dielectric heating adhesive sheet surface AS1 and the second high-frequency dielectric heating adhesive sheet surface AS2. In FIG. 4, W is 190 mm, L is 250 mm, W1 is 7 mm, and L1 is 7 mm. W is the width dimension of the high-frequency dielectric heating adhesive sheet AS. L is the length dimension of the adhesive sheet AS for high-frequency dielectric heating. W1 is the dimension of the frame-shaped portion Fr in the width direction of the adhesive sheet AS for high-frequency dielectric heating. L1 is the dimension of the frame-shaped portion Fr in the length direction of the adhesive sheet AS for high-frequency dielectric heating. As mentioned above, the thickness of the frame-shaped portion Fr of the adhesive sheet AS for high-frequency dielectric heating is 400 μm.

[0143] The thermoplastic resin (A) and the dielectric filler (B) shown in Table 1 are explained below.

[0144] (Thermoplastic resin (A)) [Styrene-based thermoplastic elastomer (a1)] SEBS: styrene-(ethylene / butylene)-styrene copolymer (manufactured by Asahi Kasei Corporation, trade name "Tuftec H1043", styrene content 67% by mass). SEBS is a hydrogenated product of a styrene-based copolymer resin. SEPS: styrene-(ethylene / propylene)-styrene copolymer (manufactured by Kuraray Co., Ltd., trade name "Septon 2002", styrene content 30% by mass). SEPS is a hydrogenated product of a styrene-based copolymer resin.

[0145] [Thermoplastic resin (a2)] PP-1: Polypropylene resin (manufactured by Prime Polymer Co., Ltd., product name "Prime Polypro J108M"). PP-2: Propylene block copolymer (manufactured by SunAllomer Co., Ltd., product name "SunAllomer VMD81M"). PP-3: Polypropylene resin (manufactured by Prime Polymer Co., Ltd., product name "Prime Polypro F-744NP"). m-PPE: Modified polyphenylene ether (manufactured by Asahi Kasei Corporation, product name "Zylon 200H"). Modified polyphenylene ether is a polymer alloy in which polyphenylene ether is compounded with polystyrene.

[0146] (Dielectric Filler (B)) ZnO: Zinc oxide (manufactured by Hakusui Tech Co., Ltd., product name "DW-4").

[0147] The volume average particle diameter of the dielectric filler (B) was measured by a laser diffraction / scattering method using a laser diffraction particle size distribution measuring device (manufactured by Malvern Panalytical, product name "Mastersizer 3000"), and the volume average particle diameter was calculated from the results of the particle size distribution measurement in accordance with JIS Z 8819-2: 2019. The volume average particle diameter of the dielectric filler (B) measured by the above method was 4 μm.

[0148] [Evaluation of Physical Properties of High-Frequency Dielectric Heating Adhesive] The high-frequency dielectric heating adhesive of each example prepared was evaluated as follows.

[0149] <Storage modulus (E')> The adhesive sheet for high-frequency dielectric heating prepared in each example was cut into a size of 10 mm in length and 5 mm in width. The storage modulus of the cut adhesive sheet for high-frequency dielectric heating was measured in the temperature range of -50°C to 150°C using a dynamic viscoelasticity measuring device (manufactured by NETZSCH, product name "DMA242E Artemis") under conditions of a frequency of 10 Hz, an amplitude of 5 μm, and a heating rate of 3°C / min. The value of the storage modulus at 110°C was obtained from the measured storage modulus.

[0150] <Complex viscosity (η ＊The granular pellets prepared above were dried at 80°C for 6 hours, and then pressed in a heat press under a predetermined temperature and load to produce a 1000 μm thick high-frequency dielectric heating adhesive sheet, which was then cut into a 20 mm diameter piece. The complex viscosity of the cut high-frequency dielectric heating adhesive sheet was measured using a dynamic viscoelasticity measuring device (manufactured by Anton Paar, product name "Modular Compact Rheometer MCR302") at a temperature of 220°C, a shear strain of 0.1%, and an angular frequency range of 0.1 rad / s to 600 rad / s. From the measured complex viscosity, the complex viscosity value at a 220°C environment and an angular frequency of 600 rad / s as a shear rate was obtained.

[0151] <Dielectric Properties> The granular pellets prepared above were dried at 80°C for 6 hours, and then a 400 μm thick high-frequency dielectric heating adhesive sheet was produced using a heat press under a specified temperature and load. This was then cut into a 50 mm long x 50 mm wide piece. The cut high-frequency dielectric heating adhesive sheet was measured for its relative permittivity (ε'r) and dielectric loss tangent (tanδ) using a parallel plate method at 23°C and a frequency of 40.68 MHz using a dielectric material test fixture 16453A (Agilent). Based on the measurement results, the dielectric properties (tanδ / ε'r) were calculated.

[0152] <Injection moldability> Injection molding was carried out according to the procedure described above for the preparation of the high-frequency dielectric heating adhesive, and the adhesive sheet for high-frequency dielectric heating in each example was evaluated for suitability for injection molding in the production process according to the following evaluation criteria.

[0153] (Evaluation criteria) A: Injection molding possible F: Injection molding not possible due to insufficient filling

[0154] <Adhesive Strength> Two modified polyphenylene ether resin test pieces (25 mm long x 70 mm wide x 5 mm thick) were prepared as adherends. The prepared high-frequency dielectric heating adhesive sheet was cut to dimensions of 25 mm long x 7 mm wide. The cut high-frequency dielectric heating adhesive sheet was placed between two adherends and laminated. The adherend and high-frequency dielectric heating adhesive sheet laminated as described above were fixed between two electrodes of a high-frequency dielectric heating device (manufactured by Yamamoto Vinita Co., Ltd., product name "YRP-400T-A"). Next, while in the fixed state, an electric field was applied under the high-frequency electric field application conditions described below to bond the high-frequency dielectric heating adhesive sheet and the adherend, thereby preparing a test piece for adhesiveness evaluation. The pressing pressure during high-frequency electric field application was the initial setting value for the pressure applied to the high-frequency dielectric heating adhesive sheet.

[0155] (High frequency electric field application conditions) Frequency: 40.68 MHz Output: 30 W Application time: 50 seconds Pressing pressure: 0.2 MPa

[0156] The obtained test pieces were left to stand for 24 hours in an environment of 23°C and 50% RH, and then the tensile shear strength (unit: MPa) was measured as the adhesive strength in an environment of 23°C using a universal tensile tester (Instron 5581, manufactured by Instron Corporation). The tensile shear strength was measured in accordance with JIS K 6850:1999 at a tensile speed of 5 mm / min. The adhesive strength in an environment of 110°C was measured by leaving the test pieces that had been left to stand for 24 hours in an environment of 23°C and 50% RH for 5 minutes in an environment of 110°C, and then measuring the tensile shear strength at a tensile speed of 5 mm / min.

[0157] <MVR> The MVR of the high-frequency dielectric heating adhesives prepared in each example was measured using a Shimadzu flow tester (manufactured by Shimadzu Corporation, model number "CFT-100D") The measurement conditions were a die with a hole shape of φ2.0 mm and length of 5.0 mm, a cylinder with an inner diameter of 11.329 mm, a measurement load of 5 kg, and a measurement temperature of 240°C.

[0158]

[0159]

[0160] The high frequency dielectric heating adhesive sheets of each Example are superior in injection moldability compared to the high frequency dielectric heating adhesive sheets of Comparative Examples 1, 3, 6, and 7. It is also clear that the high frequency dielectric heating adhesive sheets of each Example have higher adhesive strength in a 23°C environment and also higher adhesive strength in a 110°C environment compared to the high frequency dielectric heating adhesive sheets of Comparative Examples 2, 4, 5, and 8. The MVR of the high frequency dielectric heating adhesive in each Example is 25 cm ３ The MVR of the comparative high frequency dielectric heating adhesives with poor injection moldability was 25 cm / 10 min or more. ３ / less than 10 min.

[0161] From the above results, it was confirmed that the high-frequency dielectric heating adhesive according to this embodiment has excellent injection moldability and has excellent adhesion to the adherend regardless of environmental conditions, even when the adherend contains a styrene-based resin.

[0162] 10, 20...adhesive layer, 11...first surface, 21...second surface, 30...substrate, 40...intermediate layer, 100...structure, 1A, 1B, 1C...high frequency dielectric heating adhesive, 50...dielectric heating device, 51...electrode (first high frequency electric field application electrode), 52...electrode (second high frequency electric field application electrode), 53...high frequency power supply, 110...adherend (first adherend), 120...adherend (second adherend), Fr...frame-shaped portion, Op...opening, AS...high frequency dielectric heating adhesive sheet, AS1...first high frequency dielectric heating adhesive sheet surface, AS2...second high frequency dielectric heating adhesive sheet surface.

Claims

1. A high-frequency dielectric heating adhesive comprising: a thermoplastic resin (A) containing a styrene-based thermoplastic elastomer (a1) and a thermoplastic resin (a2) other than the styrene-based thermoplastic elastomer (a1); and a dielectric filler (B), wherein the content of the styrene component in the entire thermoplastic resin (A) is 20.0 mass% or more and 45.0 mass% or less, the storage modulus in an environment of 110°C is 300 MPa or more, and the complex viscosity in an environment of 220°C at a shear rate of 600 rad / s is 350 Pa s or less.

2. The adhesive for high-frequency dielectric heating according to claim 1, wherein the thermoplastic resin (a2) is a polyolefin resin.

3. The adhesive for high frequency dielectric heating according to claim 1 or 2, wherein the styrene-based thermoplastic elastomer (a1) contains a hydrogenated product of a styrene-based copolymer resin.

4. The adhesive for high frequency dielectric heating according to claim 1 or 2, wherein the styrene-based thermoplastic elastomer (a1) contains styrene-(ethylene / butylene)-styrene.

5. The adhesive for high frequency dielectric heating according to claim 1 or 2, wherein the thermoplastic resin (a2) contains a polypropylene-based resin.

6. A high-frequency dielectric heating adhesive according to claim 1 or 2, wherein the content of the styrene-based thermoplastic elastomer (a1) is 15.0% by volume or more and 55.0% by volume or less relative to the total amount of the high-frequency dielectric heating adhesive.

7. A high-frequency dielectric heating adhesive according to claim 1 or 2, wherein the content of the thermoplastic resin (a2) is 25.0% by volume or more and 65.0% by volume or less relative to the total amount of the high-frequency dielectric heating adhesive.

8. A high-frequency dielectric heating adhesive according to claim 1 or 2, wherein the content of the dielectric filler (B) is 3.0% by volume or more and 40.0% by volume or less relative to the total amount of the high-frequency dielectric heating adhesive.

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

10. The high-frequency dielectric heating adhesive according to claim 1 or 2, wherein the high-frequency dielectric heating adhesive is a high-frequency dielectric heating adhesive sheet.

11. The high-frequency dielectric heating adhesive according to claim 1 or 2, wherein the high-frequency dielectric heating adhesive is an injection-molded product.

12. A structure comprising: the high-frequency dielectric heating adhesive according to claim 1 or 2; and an adherend containing a styrene-based resin, wherein the adherend is bonded by the high-frequency dielectric heating adhesive.

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