Adhesive for high-frequency heating, structure, and bonding method.

Abstract

To provide a high-frequency heating adhesive in which overheating is suppressed. [Solution] The high-frequency heating adhesive contains a thermoplastic resin (A) and a filler (B) that generates heat when high frequency is applied. When high frequency of a specific frequency and output is applied to the high-frequency heating adhesive, the reference time is the time when the temperature of the high-frequency heating adhesive reaches 50°C from the start of application of the high frequency, T1 is the temperature of the high-frequency heating adhesive when the high frequency is applied for 10 seconds from the reference time, and T2 is the temperature of the high-frequency heating adhesive when the high frequency is applied for 20 seconds from the reference time. In this case, T1 is 80°C or higher, and the temperature rise rate Tr1 of the high-frequency heating adhesive, expressed by the following formula (F1), is 20% or less. Tr1(%)={(T2-T1) / T1}×100 ···(F1)

Description

Technical Field

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

Background Art

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

[0003] Patent Document 1 discloses a dielectric heat-bondable adhesive film for bonding a plurality of adherends made of the same material or different materials by dielectric heating. Said dielectric heat-bondable adhesive film comprises a polyolefin resin and a dielectric filler having an average particle diameter within a range from 1 μm to 30 μm, and has a thickness of from 10 μm to 2000 μm.

[0004] Patent Document 2 discloses a dielectric heat-bondable adhesive film for bonding a plurality of adherends made of the same material or different materials by dielectric heating using high-frequency waves with a frequency within a range from 1 MHz to 100 MHz. Said dielectric heat-bondable adhesive film comprises a polypropylene-based resin and zinc oxide, which is a dielectric filler having an average particle diameter within a range from 2 μm to 25 μm, and the thickness of said dielectric heat-bondable adhesive film is within a range from 100 μm to 1000 μm.

[0005] Patent Document 3 discloses an adhesive for high-frequency heating for bonding at least three or more adherends. Said adhesive for high-frequency heating comprises a thermoplastic resin and a dielectric filler that generates heat upon application of a high-frequency electric field, and the dielectric property DP1 of said adhesive for high-frequency heating and the dielectric property DP2 of each of said three or more adherends satisfy a specific relationship. Each of said three or more adherends is either an adherend that does not have a flow initiation temperature, or an adherend that has a flow initiation temperature, and the flow initiation temperature TF2 (°C) of said adherend and the flow initiation temperature TF1 (°C) of said adhesive for high-frequency heating satisfy a specific relationship.

Prior Art Documents

[0006] [Patent Document 1] International Publication No. 2018 / 079354 [Patent Document 2] Japanese Patent Publication No. 2019-094503 [Patent Document 3] International Publication No. 2022 / 118825 [Overview of the project] [Problems that the invention aims to solve]

[0007] When using a high-frequency heating adhesive to bond objects, applying high-frequency energy to the adhesive causes it to heat up, allowing it to bond to the object. While this is not a problem under normal operating conditions, excessive heat can occur if the high-frequency application time is prolonged. If the high-frequency heating adhesive becomes overheated, while it will bond to the object, there is a risk of damage to the contact area between the object and the adhesive.

[0008] The object of the present invention is to provide a high-frequency heating adhesive containing a thermoplastic resin and a filler that generates heat when high-frequency waves are applied, which can firmly adhere to an adherend while suppressing overheating, a structure equipped with the high-frequency heating adhesive, and a bonding method using the high-frequency heating adhesive. [Means for solving the problem]

[0009] [1] An adhesive for high-frequency heating, The aforementioned high-frequency heating adhesive is A thermoplastic resin (A) and a filler (B) that generates heat when high-frequency energy is applied, It contains, When a high frequency of 40.68 MHz and an output of 100 W is applied, the time when the temperature of the high-frequency heating adhesive reaches 50°C from the start of application of the high frequency is defined as the reference time, the time when the high frequency is applied for 10 seconds from the reference time is defined as the first application time, the temperature of the high-frequency heating adhesive at the first application time is defined as T1, the time when the high frequency is applied for 20 seconds from the reference time is defined as the second application time, and the temperature of the high-frequency heating adhesive at the second application time is defined as T2, The above T1 is 80°C or higher, The temperature rise rate Tr1 of the high-frequency heating adhesive, expressed by the following formula (F1) between the first application time and the second application time, is 20% or less. Adhesive for high-frequency heating. Tr1(%)={(T2-T1) / T1}×100 ···(F1)

[0010] [2] In the high-frequency heating adhesive described in [1], When the temperature of the high-frequency heating adhesive at the reference time is T0, the temperature rise rate Tr0, expressed by the following formula (F2), from the reference time to the first application time is 30% or more. Adhesive for high-frequency heating. Tr0 = {(T1 - T0) / T0} × 100 …(F2)

[0011] [3] In the high-frequency heating adhesive described in [1] or [2], When a high frequency of the aforementioned frequency and output is applied, and the point in time when the high frequency is applied for 30 seconds from the reference time is defined as the third application time, and the temperature of the high-frequency heating adhesive at the third application time is defined as T3, and the point in time when the high frequency is applied for 40 seconds from the reference time is defined as the fourth application time, and the temperature of the high-frequency heating adhesive at the fourth application time is defined as T4, The temperature rise rate Tr2 of the high-frequency heating adhesive, expressed by the following formula (F3), between the second application time and the third application time, is 15% or less. The temperature rise rate Tr3 of the high-frequency heating adhesive, expressed by the following formula (F4) between the third application time and the fourth application time, is 15% or less. An adhesive for high-frequency heating. Tr2(%)={(T3-T2) / T2}×100 ···(F3) Tr3(%)={(T4-T3) / T3}×100 ···(F4)

[0012] [4] The adhesive for high-frequency heating according to any one of [1] to [3], wherein, when a time point at which said high-frequency wave is applied for 40 seconds from said reference time is defined as a fourth application time point, and the temperature of said adhesive for high-frequency heating at said fourth application time point is defined as T4, said T4 is 220°C or lower. An adhesive for high-frequency heating.

[0013] [5] The adhesive for high-frequency heating according to any one of [1] to [4], wherein said filler (B) is a layered phosphate. An adhesive for high-frequency heating.

[0014] [6] The adhesive for high-frequency heating according to [5], wherein said layered phosphate is zirconium phosphate. An adhesive for high-frequency heating.

[0015] [7] The adhesive for high-frequency heating according to [5] or [6], wherein said layered phosphate does not support metal ions. An adhesive for high-frequency heating.

[0016] [8] The adhesive for high-frequency heating according to any one of [1] to [7], wherein the content of said filler (B) is 8.0% by volume or more and 40.0% by volume or less, relative to the entire adhesive for high-frequency heating. An adhesive for high-frequency heating.

[0017] [9] The adhesive for high-frequency heating according to any one of [1] to [8], wherein the volume-average particle diameter of said filler (B) is 0.01 μm or more and 25.0 μm or less, The volume-average particle diameter is calculated in accordance with JIS Z 8819-2:2019 based on the results of the particle size distribution measurement of the filler (B) by laser diffraction and scattering method. Adhesive for high-frequency heating.

[0018]

[10] In the high-frequency heating adhesive described in any one of items [1] to [9], The thermoplastic resin (A) is a polyolefin resin. Adhesive for high-frequency heating.

[0019]

[11] In the high-frequency heating adhesive described in any one of items [1] to

[10] , The content of the thermoplastic resin (A) is 60.0% by volume or more and 92.0% by volume or less relative to the total amount of the high-frequency heating adhesive. Adhesive for high-frequency heating.

[0020]

[12] In the high-frequency heating adhesive described in any one of items [1] to

[11] , The aforementioned high-frequency heating adhesive is a high-frequency heating adhesive sheet. Adhesive for high-frequency heating.

[0021]

[13] A structure, A high-frequency heating adhesive as described in any one of items [1] to

[12] , The object to be adhered to, Equipped with, The adherend is bonded with the high-frequency heating adhesive. structure.

[0022]

[14] A bonding method using an adhesive for high-frequency heating, The process involves applying a high frequency to a high-frequency heating adhesive described in any one of items [1] to

[12] to bond one or more adherends, The output of the aforementioned high-frequency is 10W or more and 200W or less, and the application time of the aforementioned high-frequency is 1 second or more and 20 seconds or less. Adhesion method.

[0023] A bonding method using the high-frequency heating adhesive described in

[15]

[14] , The frequency of the aforementioned high-frequency is 3 MHz or higher and 30 GHz or lower. Adhesion method. [Effects of the Invention]

[0024] According to one aspect of the present invention, a high-frequency heating adhesive containing a thermoplastic resin and a filler that generates heat when high-frequency waves are applied is provided, which can firmly adhere to an adherend while suppressing overheating, a structure equipped with the high-frequency heating adhesive, and a bonding method using the high-frequency heating adhesive. [Brief explanation of the drawing]

[0025] [Figure 1] (A) is a schematic cross-sectional view showing an example of a high-frequency heating adhesive according to this embodiment, (B) is a schematic cross-sectional view showing another example of a high-frequency heating adhesive according to this embodiment, and (C) is a schematic cross-sectional view showing another example of a high-frequency heating adhesive according to this embodiment. [Figure 2] This is a schematic cross-sectional view showing an example of a structure according to this embodiment. [Figure 3] This is a schematic diagram illustrating an example of high-frequency dielectric heating treatment using the high-frequency heating adhesive and dielectric heating device according to this embodiment. [Figure 4] This graph shows the relationship between the time during which high frequency was applied and the temperature of the high-frequency heating adhesive in Examples 1 and 2 and Comparative Examples 1 and 2. [Modes for carrying out the invention]

[0026] The following describes an example of a preferred embodiment of the present invention.

[0027] [Adhesive for high-frequency heating] The high-frequency heating adhesive according to this embodiment contains a thermoplastic resin (A) and a filler (B) that generates heat when high frequency is applied. When a high frequency of 40.68 MHz and an output of 100 W is applied to the high-frequency heating adhesive, the time when the temperature of the high-frequency heating adhesive reaches 50°C from the start of application of the high frequency is defined as the reference time, the time when the high frequency is applied for 10 seconds from the reference time is defined as the first application time, and the temperature of the high-frequency heating adhesive at the first application time is defined as T1, and the time when the high frequency is applied for 20 seconds from the reference time is defined as the second application time, and the temperature of the high-frequency heating adhesive at the second application time is defined as T2, T1 is 80°C or higher, and the temperature rise rate Tr1 of the high-frequency heating adhesive, expressed by the following formula (F1) between the first application time and the second application time, is 20% or less. Tr1(%)={(T2-T1) / T1}×100 (F1)

[0028] The high-frequency heating adhesive according to this embodiment, having the above configuration, is a high-frequency heating adhesive containing a thermoplastic resin and a filler that generates heat when high frequency is applied, which can adhere firmly to the adherend while suppressing overheating. When high frequency is applied to the high-frequency heating adhesive, if the temperature rise rate of the high-frequency heating adhesive is low in the interval between the first application point and the second application point where the application continues from the first application point, it is considered that the heating temperature of the high-frequency heating adhesive is suppressed from continuing to rise. In other words, the inventors have found that overheating of the high-frequency heating adhesive can be suppressed if the temperature rise rate Tr1, represented by the above formula (F1), is less than or equal to the above value. Therefore, the high-frequency heating adhesive according to this embodiment has the advantage that even if too much high frequency is applied, the temperature rise of the high-frequency heating adhesive is suppressed.

[0029] In this specification, the term "applying high frequency" encompasses both the application of a high-frequency electric field and the application of a high-frequency magnetic field.

[0030] The following describes the materials used in the high-frequency heating adhesive according to this embodiment.

[0031] <Thermoplastic resin (A)> The type of thermoplastic resin (A) is not particularly limited. The thermoplastic resin (A) 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 melted and having a predetermined heat resistance. It is preferable to select a type of thermoplastic resin (A) that has high affinity with the material of the adherend.

[0032] In the high-frequency heating adhesive according to this embodiment, the thermoplastic resin (A) is preferably a polyolefin resin or a styrene resin, and more preferably a polyolefin resin. If the thermoplastic resin (A) is a polyolefin resin or a styrene resin, the high-frequency heating adhesive melts easily when high frequency is applied, and the high-frequency heating adhesive according to this embodiment can be easily bonded to the adherend.

[0033] In this specification, polyolefin resins include polyolefin resins having polar moieties and polyolefin resins not having polar moieties, and when specifying the presence or absence of polar moieties, they are described as polyolefin resins having polar moieties or polyolefin resins not having polar moieties.

[0034] It is also preferable that the thermoplastic resin (A) is a polyolefin resin having polar regions. Alternatively, the thermoplastic resin (A) may be a polyolefin resin that does not have polar regions.

[0035] (Polyolefin resin) Examples of polyolefin resins as thermoplastic resin (A) include resins made of homopolymers such as polyethylene, polypropylene, polybutene, and polymethylpentene, and α-olefin resins made of copolymers of monomers selected from the group consisting of ethylene, propylene, butene, hexene, octene, and 4-methylpentene. The polyolefin resin as thermoplastic resin (A) may be a single resin or a combination of two or more resins.

[0036] [Polyolefin resins with polar regions] In polyolefin resins having polar regions, the polar regions are not particularly limited as long as they are regions that can impart polarity to the polyolefin resin. Furthermore, it is preferable that the high-frequency heating adhesive contains a polyolefin resin having polar parts as the thermoplastic resin (A), as this tends to improve dielectric properties and thus enhances adhesion to the adherend. A polyolefin-based thermoplastic resin having polar moieties may be a copolymer of an olefin monomer and a monomer having polar moieties. Alternatively, a polyolefin-based thermoplastic resin having polar moieties may be a resin obtained by introducing polar moieties into an olefin polymer obtained by polymerization of olefin monomers through modification such as an addition reaction.

[0037] There are no particular limitations on the type of olefin monomer that constitutes the polyolefin resin having polar moieties. Examples of olefin monomers include ethylene, propylene, butene, hexene, octene, and 4-methyl-1-pentene. These olefin monomers may be used individually 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. In polyolefin resins having polar regions, the olefin-derived structural units are preferably those derived from ethylene or propylene.

[0038] Examples of polar sites include hydroxyl groups, carboxyl groups, vinyl acetate structures, and acid anhydride structures. Other examples of polar sites include acid-modified structures introduced into polyolefin resins through acid modification.

[0039] Acid-modified structures, as polar sites, are sites introduced by acid modification of thermoplastic resins (e.g., polyolefin resins). Compounds used in acid modification of thermoplastic resins (e.g., polyolefin resins) include unsaturated carboxylic acid derivatives derived from unsaturated carboxylic acids, acid anhydrides of unsaturated carboxylic acids, and esters of unsaturated carboxylic acids. In this specification, polyolefin resins having acid-modified structures may be referred to as acid-modified polyolefin resins.

[0040] Examples of unsaturated carboxylic acids include acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, and citraconic acid.

[0041] Examples of acid anhydrides of unsaturated carboxylic acids include maleic anhydride, itaconic anhydride, and citraconic anhydride.

[0042] 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 tetrahydrophthalate anhydride.

[0043] [Maleic anhydride-modified polyolefin] Polyolefin resins used as thermoplastic resins more preferably have an acid anhydride structure as an acid-modified structure. The acid anhydride structure is preferably a structure introduced when the polyolefin resin is modified with maleic anhydride.

[0044] In maleic anhydride-modified polyolefins, the olefin-derived constituent units are preferably those 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.

[0045] The content (volume content) of thermoplastic resin (A) in the high-frequency heating adhesive is preferably 60.0 volume% or more, more preferably 65.0 volume% or more, even more preferably 70.0 volume% or more, even more preferably 75.0 volume% or more, and still most preferably 78.0 volume% or more. The content (volume percentage) of thermoplastic resin (A) in the high-frequency heating adhesive is preferably 92.0% by volume or less, more preferably 91.0% by volume or less, and even more preferably 90.0% by volume or less.

[0046] <Filler (B)> Filler (B) will now be described. Filler (B) is a filler that generates heat when a high frequency is applied. Preferably, filler (B) is a filler that generates heat when a high frequency magnetic field is applied and when a high frequency electric field is applied.

[0047] One embodiment of filler (B) is a filler that generates heat when a high frequency with a frequency range of 1 kHz or more and 30 GHz or less is applied. Another embodiment of filler (B) is a filler that generates heat when a high frequency with a frequency range of 3 MHz or more and 30 GHz or less is applied. Filler (B) may generate heat when a high frequency with a frequency range of 1 kHz or more and 3 MHz or less is applied, may generate heat when a high frequency with a frequency range of 3 MHz or more and 300 MHz or less is applied, or may generate heat when a high frequency with a frequency range of 300 MHz or more and 30 GHz or less is applied. From the viewpoint of making it easier to suppress overheating of the high-frequency heating adhesive and from the viewpoint of being able to selectively and uniformly heat the necessary parts, it is preferable that filler (B) is a filler that generates heat when a high frequency with a frequency range of at least 3 MHz or more and 300 MHz is applied. It is preferable that filler (B) is a filler that generates heat when a high frequency such as 13.56 MHz, 27.12 MHz, or 40.68 MHz is applied, among the frequency range of 3 MHz or more and 300 MHz or less. Furthermore, it is preferable that the filler (B) is a filler that generates heat when a high frequency of, for example, 2.45 GHz is applied, within the frequency range of 300 MHz or higher and 30 GHz or lower.

[0048] The type of filler (B) is not particularly limited, as long as it generates heat when high-frequency waves in the above frequency range are applied and the temperature rise rate Tr1 of the high-frequency heating adhesive satisfies the above formula (F1). Filler (B) may be an organic filler or an inorganic filler. Filler (B) is preferably an inorganic filler. From the viewpoint of suppressing overheating of the high-frequency heating adhesive, filler (B) is preferably a layered phosphate. The layered phosphate may be a layered phosphate of a trivalent metal or a layered phosphate of a tetravalent metal. Examples of layered phosphates include, specifically, at least one selected from the group consisting of zirconium phosphate, titanium phosphate, germanium phosphate, tin phosphate, lead phosphate, hafnium phosphate, cerium phosphate, lithium iron phosphate, and aluminum tripolyphosphate. The particle shape of the layered phosphate is preferably, for example, a two-dimensional layered structure.

[0049] Among these, from the viewpoint of suppressing overheating of the high-frequency heating adhesive, the filler (B) is preferably a layered phosphate of a tetravalent metal, and more preferably zirconium phosphate.

[0050] From the viewpoint of suppressing overheating of the high-frequency heating adhesive, it is preferable that the layered phosphate is not intercalated. In one embodiment of the layered phosphate, it is preferable that it does not support metal ions. Examples of such metal ions include at least one metal ion selected from the group consisting of silver, mercury, zinc, copper, iron, lead, platinum, molybdenum, and nickel.

[0051] The content (volume percentage) of filler (B) in the high-frequency heating adhesive is preferably 8.0 volume% or more, more preferably 9.0 volume% or more, and even more preferably 10.0 volume% or more. The content (volume content) of filler (B) in the high-frequency heating adhesive is preferably 40.0 volume% or less, more preferably 35.0 volume% or less, even more preferably 30.0 volume% or less, even more preferably 25.0 volume% or less, and still more preferably 22 volume% or less.

[0052] By having a volume content of filler (B) of 8.0% by volume or more in the high-frequency heating adhesive, the heat generation is improved, making it easier to firmly bond the high-frequency heating adhesive to the adherend. By having a volume content of filler (B) in the high-frequency heating adhesive of 40.0% by volume or less, a decrease in the strength of the adhesive can be prevented, and as a result, a decrease in adhesive strength can be prevented by using this adhesive. Furthermore, when the shape of the high-frequency heating adhesive according to this embodiment is an adhesive sheet, having a volume content of filler (B) in the adhesive sheet of 40.0% by volume or less makes it easier to obtain flexibility as a sheet and to prevent a decrease in toughness, so that the high-frequency heating adhesive sheet can be easily processed into the desired shape in a subsequent process.

[0053] The volume-average particle diameter of filler (B) is preferably 0.01 μm or more, more preferably 0.03 μm or more, even more preferably 0.05 μm or more, even more preferably 0.07 μm or more, even more preferably 0.10 μm or more, and still most preferably 0.15 μm or more. The volume-average particle size of filler (B) is preferably 25.0 μm or less, more preferably 15.0 μm or less, even more preferably 5.0 μm or less, even more preferably 3.0 μm or less, and particularly preferably 1.0 μm or less.

[0054] Because the volume-average particle size of filler (B) is 0.01 μm or larger, the high-frequency heating adhesive exhibits high heat generation performance when high frequency is applied, and can adhere firmly to the substrate in a short time. By having a volume-average particle diameter of filler (B) of 25.0 μm or less, the high-frequency heating adhesive exhibits high heat generation performance when high frequency is applied, and can firmly adhere to the adherend in a short time. Furthermore, if the high-frequency heating adhesive according to this embodiment is an adhesive sheet, having a volume-average particle diameter of filler (B) of 25.0 μm or less prevents a decrease in the strength of the high-frequency heating adhesive sheet.

[0055] The volume-average particle size of filler (B) is measured by the following method: The particle size distribution of filler (B) is measured by laser diffraction and scattering, and the volume-average particle size is calculated from the results of this particle size distribution measurement in accordance with JIS Z 8819-2:2019.

[0056] <Additives> The high-frequency heating adhesive according to this embodiment may or may not contain additives, as long as they do not hinder adhesion in a short time.

[0057] If the high-frequency heating adhesive according to this embodiment contains additives, examples of additives include tackifiers, plasticizers, waxes, colorants, antioxidants, UV absorbers, antibacterial agents, coupling agents, viscosity modifiers, organic fillers, and inorganic fillers. The organic and inorganic fillers used as additives are different from filler (B).

[0058] Tackifiers and plasticizers can improve the melting and bonding properties of high-frequency heating adhesives. Examples of tackifiers include rosin derivatives, polyterpene resins, aromatically modified terpene resins, hydrides of aromatically modified terpene resins, terpene phenol resins, coumarone-indene resins, aliphatic petroleum resins, aromatic petroleum resins, and hydrides of 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.

[0059] When the high-frequency heating adhesive according to this embodiment contains additives, the content of the additives in the high-frequency 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 heating adhesive. Furthermore, the content of the additives in the high-frequency 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.

[0060] The high-frequency heating adhesive according to this embodiment preferably does not contain a solvent. A solvent-free high-frequency heating adhesive is less likely to cause problems with volatile organic compounds caused by the adhesive used for bonding to the adherend.

[0061] The high-frequency heating adhesive according to this embodiment preferably does not contain conductive materials such as carbon or carbon compounds mainly composed of carbon and metals. The high-frequency heating adhesive according to this embodiment preferably does not contain conductive materials composed of metals such as carbon steel, alpha iron, gamma iron, delta iron, copper, iron oxide, brass, aluminum, iron-nickel alloys, and iron-nickel-chromium alloys, nor conductive materials composed of carbon or carbon compounds mainly composed of carbon such as coke, gaseous carbon, anthracite, flake graphite, earthy graphite, coke-based artificial graphite, carbon black-based artificial graphite, pyrolysis-based artificial graphite, kitsch graphite, carbon fiber, and carbon black.

[0062] In this embodiment, from the viewpoint of adhesion to the adherend, it is preferable that the high-frequency heating adhesive does not contain modified lignin such as glycol lignin as other additives.

[0063] In the high-frequency heating adhesive according to this embodiment, the total content of thermoplastic resin (A) and 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 still more preferably 99% by mass or more.

[0064] <Characteristics of adhesives for high-frequency heating> Next, the characteristics of the high-frequency heating adhesive according to this embodiment will be described.

[0065] (Temperature rise rate) In this embodiment, when a high frequency of 40.68 MHz and an output of 100 W is applied to the high-frequency heating adhesive, the temperature rise rate Tr1 of the high-frequency heating adhesive, expressed by the following formula (F1), is 20% or less. Tr1(%)={(T2-T1) / T1}×100 (F1)

[0066] In the above formula (F1), T1 is the temperature of the high-frequency heating adhesive at the first application time, with the reference time being the point when the temperature of the high-frequency heating adhesive reaches 50°C from the start of application of a high frequency with a frequency of 40.68 MHz and an output of 100 W, and the first application time being the point when the high frequency is applied for 10 seconds from the reference time. T2 is the temperature of the high-frequency heating adhesive at the second application time, with the second application time being the point when the high frequency is applied for 20 seconds from the reference time.

[0067] The temperature rise rate Tr1 is preferably 15% or less, more preferably 14% or less, and even more preferably 13% or less. If the temperature rise rate Tr1 is 15% or less, overheating of the high-frequency heating adhesive is suppressed. The lower limit of the temperature rise rate Tr1 is 0% or more.

[0068] In the high-frequency heating adhesive according to this embodiment, from the viewpoint of facilitating bonding between the adherend and the high-frequency heating adhesive in a short time, it is preferable that the temperature rise rate Tr0, expressed by the following formula (F2), from the reference time to the first application time, when the temperature T0 of the high-frequency heating adhesive at the reference time is set to 30% or more. In the following formula (F2), T1 is as described above. Tr0 = {(T1 - T0) / T0} × 100 …(F2)

[0069] The temperature rise rate Tr0 is more preferably 40% or more, even more preferably 50% or more, even more preferably 70% or more, even more preferably 90% or more, and even more preferably 100% or more. If the temperature rise rate Tr0 is 30% or more, the adherend and the high-frequency heating adhesive can be bonded in a short time. There is no particular upper limit to the temperature rise rate, for example, it may be 250% or less.

[0070] In the high-frequency heating adhesive according to this embodiment, the temperature T1 is 80°C or higher. From the viewpoint of obtaining stronger adhesion with the adherend, the temperature T1 is preferably 85°C or higher, more preferably 90°C or higher, even more preferably 95°C or higher, even more preferably 100°C or higher, and still more preferably 120°C or higher. The upper limit of the temperature T1 is not particularly limited. From the viewpoint of making it easier to suppress overheating of the high-frequency heating adhesive, the temperature T1 can be, for example, 200°C or lower.

[0071] In the high-frequency heating adhesive according to this embodiment, from the viewpoint of suppressing overheating of the high-frequency heating adhesive, it is preferable that a high frequency of 40.68 MHz and an output of 100 W is applied, and the point in time when the high frequency is applied for 30 seconds from the reference time is defined as the third application time, the temperature of the high-frequency heating adhesive at the third application time is defined as T3, and the temperature rise rate Tr2 of the high-frequency heating adhesive, expressed by the following formula (F3) from the second application time to the third application time, is 15% or less. In the following formula (F3), T2 is as described above. Tr2(%)={(T3-T2) / T2}×100 ···(F3)

[0072] The temperature rise rate Tr2 is preferably 13% or less, more preferably 10% or less, and even more preferably 5% or less. If the temperature rise rate Tr2 is 15% or less, overheating of the high-frequency heating adhesive is more easily suppressed even when high-frequency power is continuously applied. The lower limit of the temperature rise rate Tr2 is 0% or more.

[0073] In the high-frequency heating adhesive according to this embodiment, from the viewpoint of suppressing overheating of the high-frequency heating adhesive, in formula (F4), T4 is the temperature T4 of the high-frequency heating adhesive at the time when a high frequency of 40.68 MHz and an output of 100 W is applied and the high frequency is applied for 40 seconds from the reference time, and it is preferable that the temperature rise rate Tr3 of the high-frequency heating adhesive, expressed by the following formula (F4) from the third application time to the fourth application time, is 15% or less. In the following formula (F4), T3 is as described above. Tr3(%)={(T4-T3) / T3}×100 ···(F4)

[0074] The temperature rise rate Tr3 is preferably 13% or less, more preferably 10% or less, and even more preferably 5% or less. If the temperature rise rate Tr3 is 15% or less, overheating of the high-frequency heating adhesive is further suppressed even when high-frequency power is continuously applied. The lower limit of the temperature rise rate Tr3 is 0% or more.

[0075] In the high-frequency heating adhesive according to this embodiment, the temperature T4 is preferably 220°C or lower, from the viewpoint of suppressing overheating of the high-frequency heating adhesive. Similarly, the temperature T4 is preferably 210°C or lower, more preferably 200°C or lower, even more preferably 190°C or lower, even more preferably 180°C or lower, and still more preferably 175°C or lower. The temperature T4 is preferably 100°C or higher, more preferably 105°C or higher, even more preferably 110°C or higher, even more preferably 115°C or higher, and still more preferably 120°C or higher, from the viewpoint of obtaining strong adhesion with the adherend.

[0076] The aforementioned temperature rise rates Tr0, Tr1, Tr2, and Tr3 are determined by the following procedure. Specifically, the aforementioned temperature rise rates Tr0, Tr1, Tr2, and Tr3 can be measured by the method described in the "Examples" section below, and the high-frequency application conditions can be specifically those described in the "Examples" section below.

[0077] (ST1): First, a high frequency of 40.68 MHz and an output of 100 W are applied to the high-frequency heating adhesive according to this embodiment. The reference time is defined as the point in time when the temperature of the high-frequency heating adhesive according to this embodiment reaches 50°C after the start of the high-frequency application under the above conditions. This reference time temperature is defined as T0. To explain the reference time, since the temperature of the high-frequency heating adhesive may rise instantaneously, for example, in less than 1 second after the start of application of the high frequency, the point in time when the temperature reaches 50°C is defined as the reference time to ensure the accuracy of the evaluation of the temperature rise rate.

[0078] (ST2): Next, the point in time when the high frequency under the above conditions has been applied for 10 seconds from the reference time is defined as the first application time. The temperature of the high-frequency heating adhesive measured at the first application time is defined as T1.

[0079] (ST3): Next, the point in time when the high frequency under the above conditions has been applied for 20 seconds from the reference time is defined as the second application time. The temperature of the high-frequency heating adhesive measured at the second application time is defined as T2.

[0080] (ST4): Next, the point in time when the high frequency under the above conditions has been applied for 30 seconds from the reference time is defined as the third application time. The temperature of the high-frequency heating adhesive measured at the third application time is defined as T3.

[0081] (ST5): Next, the point in time when the high frequency under the above conditions has been applied for 40 seconds from the reference time is defined as the fourth application time. The temperature of the high-frequency heating adhesive measured at the fourth application time is defined as T4.

[0082] (ST6): From the temperature T0 and temperature T1 values ​​measured in (ST1) and (ST2), the rate of temperature rise Tr0 within the interval from the reference time to the first application time is determined by the formula (F2).

[0083] Similarly, the temperature rise rate Tr1 within the interval from the first application time to the second application time is determined from the temperature T1 and temperature T2 values ​​measured in (ST2) and (ST3) using the formula (F1).

[0084] Similarly, the rate of temperature rise Tr2 within the interval from the second application time to the third application time is determined from the values ​​of temperature T2 and temperature T3 measured in (ST3) and (ST4) using formula (F3), and the rate of temperature rise Tr3 within the interval from the third application time to the fourth application time is determined from the values ​​of temperature T3 and temperature T4 measured in (ST4) and (ST5) using formula (F4).

[0085] <Shape of adhesive for high-frequency heating> The shape of the high-frequency heating adhesive according to this embodiment is not particularly limited. The high-frequency heating adhesive according to this embodiment may be a molded adhesive obtained by injection molding or the like, molded into the desired shape, or it may be a sheet-like adhesive obtained by extrusion molding or the like. In this embodiment, the molded body and the sheet are different shapes. A sheet usually refers to a long strip or sheet-like form 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 heating adhesive, and refers to various shapes other than a sheet.

[0086] The high-frequency heating adhesive according to this embodiment is preferably in sheet form. That is, the high-frequency heating adhesive according to this embodiment is preferably a high-frequency heating adhesive sheet (sometimes referred to as an adhesive sheet). Having the high-frequency heating adhesive as an adhesive sheet further shortens the manufacturing process time for the structure.

[0087] The shape of the high-frequency heating adhesive according to this embodiment may be that of a frame-shaped sheet (frame-shaped adhesive sheet) having a frame-shaped portion and an opening that penetrates from one surface to the other on two opposing surfaces. The shape of the opening is not particularly limited. If the adhesive sheet is frame-shaped, the frame-shaped adhesive sheet may have one opening or two or more. The frame-shaped sheet may have a notch in part of the frame-shaped portion. In this case, the opening may be shaped so that part of the frame-shaped portion communicates with the outside of the frame-shaped portion. That is, in a plan view of the frame-shaped sheet, the frame-shaped portion may have an open shape (for example, a discontinuous shape of the frame-shaped portion such as a C-shape or a U-shape). The frame-shaped sheet may not have a notch in the frame-shaped portion. In this case, the opening may be shaped so that the periphery of the opening is surrounded by the frame-shaped portion (for example, a continuous shape of the frame-shaped portion such as an O-shape). That is, in a plan view of the frame-shaped sheet, the frame-shaped portion may have a closed shape. If the frame-shaped sheet has two or more openings, the shape of the openings may be a combination of openings of the same shape or a combination of openings of different shapes when viewed in plan from the frame-shaped sheet. The shape of the high-frequency heating adhesive according to this embodiment may be a sheet without such openings. Furthermore, the high-frequency heating adhesive according to this embodiment can also be molded into an adhesive sheet of the desired shape by molding methods such as extrusion molding and injection molding.

[0088] In one embodiment, the high-frequency heating adhesive according to this embodiment consists of only one adhesive layer made of the high-frequency heating adhesive sheet according to this embodiment. When the high-frequency heating adhesive is a high-frequency heating adhesive sheet consisting of only one adhesive layer, the adhesive layer itself corresponds to the high-frequency heating adhesive sheet, and therefore the form and characteristics of the high-frequency heating adhesive sheet correspond to the form and characteristics of the adhesive layer. It is preferable that the high-frequency heating adhesive sheet consists of only a single adhesive layer. This makes it possible to reduce the thickness of the high-frequency heating adhesive sheet and to easily mold the high-frequency heating adhesive sheet.

[0089] Since high-frequency heating adhesive sheets may consist of only one layer of high-frequency heating adhesive, the terms "high-frequency heating adhesive sheet" and "adhesive layer" may, in some cases, be interchangeable within this specification.

[0090] The high-frequency heating adhesive according to this embodiment is not limited to a high-frequency heating adhesive sheet consisting of only one adhesive layer. The high-frequency heating adhesive according to this embodiment may be any of the embodiments shown in Figures 1(A), 1(B), and 1(C).

[0091] The high-frequency heating adhesive 1A shown in Figure 1(A) is an adhesive sheet consisting of only a single adhesive layer 10.

[0092] The high-frequency heating adhesive 1B shown in Figure 1(B) is an adhesive sheet having an adhesive layer 10 and a base material 30 that supports the adhesive layer 10. The adhesive layer 10 has a first surface 11. The base material 30 is not particularly limited as long as it is a member that can support the adhesive layer 10. Examples of the base material 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 base material 30 may contain a filler that generates heat when high frequency is applied. The filler (B) in the adhesive layer 10 and the filler in the base material 30 are either the same or different from each other.

[0093] The high-frequency heating adhesive 1C shown in Figure 1(C) is an adhesive sheet having an intermediate layer 40 disposed between an adhesive layer 10 and an adhesive layer 20. The high-frequency heating adhesive 1C has a first surface 11 and a second surface 21 opposite to the first surface 11. In the high-frequency heating adhesive 1C, it is sufficient that the adhesive layer 10 satisfies the conditions for the adhesive layer of the high-frequency heating adhesive sheet according to this embodiment. In one embodiment, both the adhesive layer 10 and the adhesive layer 20 are layers with the same composition and properties. In one embodiment, the adhesive layer 20 is a high-frequency heating adhesive layer that differs from the adhesive layer 10 in at least one respect of composition and properties. In one embodiment, the adhesive layer 20 is a general adhesive layer that is not a high-frequency heating adhesive layer. In this case, the non-high-frequency heating adhesive layer 20 is, for example, a dry-solidifying adhesive layer that dries and solidifies as water or a solvent evaporates, or a layer of adhesive formed from an adhesive.

[0094] When the high-frequency 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 thicker, the heat generation of the adhesive sheet in contact with the adherend is improved when high-frequency current is applied, making it easier to firmly bond the adhesive sheet to the adherend in a short time. In addition, when bonding to the adherend, the adhesive sheet can more easily conform to the unevenness of the adherend, making it easier to achieve strong adhesive strength.

[0095] When the adhesive sheet has a multilayer structure consisting of multiple layers, the thickness of the adhesive layer is preferably 5 μm or more, more preferably 10 μm or more, even more preferably 30 μm or more, and even more preferably 50 μm or more. If the adhesive sheet for high-frequency heating is a multi-layered sheet, and the thickness of the adhesive layer is 5 μm or more, the adhesive layer will conform more easily to the unevenness of the adherend when bonding with the adherend, and the adhesive strength will be more easily achieved.

[0096] There is no particular upper limit to the thickness of the adhesive sheet. As the thickness of the adhesive sheet increases, the weight of the entire structure obtained by bonding the adhesive sheet to the adherend also increases. For this reason, it is preferable that the thickness of the adhesive sheet be within a range that does not cause problems in practical use, such as processability and handling. Considering the practicality and moldability of the adhesive sheet for high-frequency heating, 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 thickness of the adhesive sheet is preferably the above value regardless of whether the configuration consists of only one adhesive layer or a multilayer configuration consisting of multiple layers including an adhesive layer.

[0097] Adhesive sheets used as adhesives for high-frequency heating are easier to handle and offer improved workability when bonding to the substrate compared to using liquid adhesives that require application.

[0098] Furthermore, adhesive sheets used as adhesives for high-frequency heating allow for appropriate control of sheet thickness and other parameters. Therefore, adhesive sheets can be applied to roll-to-roll systems, and can be processed to any desired area and shape through die-cutting or other methods to match the bonding area with the adherend and the shape of the adherend. Thus, adhesive sheets used as adhesives for high-frequency heating offer significant advantages from a manufacturing process perspective.

[0099] The high-frequency heating adhesive according to this embodiment can adhere to the adherend even with dielectric heating, and therefore it is preferable to use it by applying a high-frequency electric field in the frequency band known as short wave to very short wave. Applying a high-frequency electric field in this frequency band increases the heating depth, thus improving the heat generation when high-frequency is applied. For this reason, even when the thickness of the high-frequency heating adhesive is thick, it is easy to firmly bond the adhesive sheet and the adherend in a short time.

[0100] <Method for manufacturing adhesive for high-frequency heating> The high-frequency heating adhesive according to this embodiment can be manufactured, for example, by mixing the above-mentioned components. If the high-frequency heating adhesive according to this embodiment is an adhesive sheet, for example, the above-mentioned components can be pre-mixed, kneaded using a known kneading device such as an extruder and a hot roll, and manufactured by a known molding method such as extrusion molding, calendering, injection molding, and casting molding. If the high-frequency heating adhesive according to this embodiment is a molded body, for example, it can be manufactured using a material obtained by pre-mixing the above-mentioned components by a known molding method such as injection molding and compression molding. Furthermore, if the high-frequency heating adhesive according to this embodiment is a frame-shaped sheet, the frame-shaped sheet can be manufactured by providing openings in the sheet-like high-frequency heating adhesive obtained by the above-mentioned adhesive sheet molding method, for example, by a known punching process. Alternatively, the frame-shaped sheet can be manufactured in the above-mentioned adhesive sheet molding method by using a mold with a shape that provides the desired openings.

[0101] High-frequency heating adhesives offer superior water and moisture resistance compared to general adhesives.

[0102] The high-frequency heating adhesive according to this embodiment is heated locally by the application of high frequency. Therefore, the high-frequency heating adhesive according to this embodiment makes it easier to prevent the problem of the entire adherend being damaged during adhesion.

[0103] [Adherend] The material of the adherend is not particularly limited. The adherend may be an organic material, a metallic material, or an inorganic material, or a composite material thereof.

[0104] The material of the adherend is preferably an organic material. Examples of organic materials for 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; nylon 6 and nylon 66, etc., polyester resin; polyethylene terephthalate and polybutylene terephthalate resin, etc., 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 a foamed organic material. In addition to these, other organic materials for the adherend include, for example, highly heat-resistant organic materials such as super engineering plastics. The high-frequency heating adhesive according to this embodiment has excellent heat resistance. In this respect, it is also preferable that the adherend contains a highly heat-resistant organic material.

[0105] If 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 heating adhesive may be different resins. In this case, bonding becomes easier without damaging the shape of the adherend.

[0106] Furthermore, if the material of the adherend is a thermoplastic resin, from the viewpoint of adhesion, 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 heating adhesive.

[0107] In this specification, "main composition of the thermoplastic resin" means, for example, if the thermoplastic resin is a polymer, the repeating unit that is present in the greatest quantity among the repeating units contained in the polymer. If the thermoplastic resin is a polymer derived from a single monomer, the repeating units of that monomer unit are the "main composition of the thermoplastic resin". If the thermoplastic resin is a copolymer, the repeating unit that is present in the greatest quantity among the polymer is the "main composition of the thermoplastic resin". If the thermoplastic resin is a copolymer, the "main composition of the thermoplastic resin" in the copolymer is a repeating unit that is present in 30% by mass or more, in one embodiment it is a repeating unit that is present in more than 30% by mass, in another embodiment it is a repeating unit that is present in 40% by mass or more, and in yet another embodiment it is a repeating unit that is present in 50% by mass or more. Furthermore, if the thermoplastic resin is a copolymer, there may be two or more repeating units that are present in the greatest quantity.

[0108] Examples of inorganic materials used as the adherend include glass materials, cement materials, ceramic materials, and metal materials. The adherend may also be a fiber-reinforced resin, which is a composite material of fibers and the aforementioned plastic material. The plastic material in this fiber-reinforced resin is at least one selected from the group consisting of, for example, polypropylene resin, polyethylene resin, polyurethane resin, acrylonitrile-butadiene-styrene copolymer resin, polycarbonate resin, polyamide resin; nylon 6 and nylon 66, etc., polyester resin polyethylene terephthalate and polybutylene terephthalate resin, etc., polyacetal resin, polymethyl methacrylate resin, epoxy resin, and polystyrene resin. Examples of fibers in the fiber-reinforced resin include glass fibers, Kevlar® fibers, and carbon fibers.

[0109] The adherend is preferably one with low conductivity.

[0110] When bonding multiple adherends using the high-frequency heating adhesive according to this embodiment, the multiple adherends may be made of the same material or different materials.

[0111] The shape of the adherend is not particularly limited, but if the high-frequency heating adhesive according to this embodiment is an adhesive sheet, the adherend preferably has a surface on which adhesive sheets can be bonded, and is preferably in the form of a sheet, plate, or block. When bonding multiple adherends together, the shapes and dimensions of the adherends may be the same or different.

[0112] [Structure] The structure according to this embodiment comprises a high-frequency heating adhesive according to this embodiment and a adherend, wherein the adherend is bonded by the high-frequency heating adhesive. In one embodiment of the structure according to this embodiment, it is preferable that one or more adherends are bonded by the high-frequency heating adhesive according to this embodiment. It is preferable that the structure according to this embodiment is a structure in which one or more adherends are laminated on the high-frequency heating adhesive. Furthermore, one embodiment of the structure according to this embodiment may be a structure in which two or more adherends are laminated via the high-frequency heating adhesive. Hereinafter, the case in which the structure according to this embodiment comprises two adherends will be described with reference to the drawings.

[0113] Figure 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 and a second adherend 120, and a high-frequency heating adhesive 1A, the high-frequency heating adhesive 1A being positioned 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 heating adhesive 1A, and the second adherend 120 are stacked 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 positioned so that the longitudinal centers of the first adherend 110, the high-frequency heating adhesive 1A, and the second adherend 120 are aligned. The high-frequency heating adhesive 1A is a high-frequency heating adhesive according to this embodiment.

[0114] In the structure according to this embodiment, the position and thickness of the high-frequency heating adhesive are not limited to those shown in Figure 2. In the structure according to this embodiment, the shape, size, and number of adherends are not limited to those shown in Figure 2. The structure according to this embodiment is not limited to a structure in which two adherends are laminated with a high-frequency heating adhesive in between, as shown in Figure 2.

[0115] [Adhesion method] Next, as an example of an adhesive method for bonding an object to a substrate using the high-frequency heating adhesive according to this embodiment, a method for manufacturing a structure by bonding the high-frequency heating adhesive according to this embodiment to an object to be bonded will be described.

[0116] The bonding method using the high-frequency heating adhesive according to this embodiment comprises the step of applying high frequency to the high-frequency heating adhesive according to this embodiment to bond one or more adherends. In one aspect of the bonding method using the high-frequency heating adhesive according to this embodiment, it is preferable that in the above step, the output of the high frequency applied to the high-frequency heating adhesive is 10W or more and 200W or less, and the application time of the high frequency is 1 second or more and 20 seconds or less. By having a high-frequency output of 10W or more and 200W or less, and an application time of 1 second or more and 20 seconds or less, overheating when high frequency is applied to the high-frequency heating adhesive according to this embodiment is easily suppressed. The output of the high frequency indicates the amount of energy transferred to the object, and the frequency of the high frequency indicates the way (speed) of energy transfer. Note that the application time here is the application time starting from the time the application is started, not the application time starting from the time when the temperature reaches 50°C.

[0117] If the high-frequency output is 10W or higher, the problem of the temperature not rising easily during high-frequency heating treatment can be prevented, making it easier to obtain good adhesive strength. If the high-frequency output is 200W or less, it is easier to prevent problems that would arise from difficulty in temperature control due to high-frequency heating treatment.

[0118] If the high-frequency current is applied for 1 second or longer, the problem of the temperature not rising easily during dielectric heating treatment can be prevented, making it easier to obtain good adhesive strength. If the high-frequency application time is 20 seconds or less, it is easier to prevent problems such as decreased manufacturing efficiency of the structure, increased manufacturing costs, and thermal degradation of the adherend.

[0119] In one embodiment of the bonding method using the high-frequency heating adhesive according to this embodiment, the output of the high frequency applied to the high-frequency heating adhesive is preferably 15W or more, preferably 20W or more, preferably 25W or more, and preferably 30W or more. In one embodiment of the bonding method using the high-frequency heating adhesive according to this embodiment, the output of the high frequency applied to the high-frequency heating adhesive is preferably 190W or less, more preferably 170W or less, even more preferably 150W or less, even more preferably 120W or less, even more preferably 110W or less, and still even more preferably 100W or less.

[0120] In one embodiment of the bonding method using the high-frequency heating adhesive according to this embodiment, the application time of the high frequency applied to the high-frequency heating adhesive is preferably 2 seconds or more, preferably 3 seconds or more, preferably 4 seconds or more, and preferably 5 seconds or more. In one embodiment of the bonding method using the high-frequency heating adhesive according to this embodiment, the application time of the high frequency applied to the high-frequency heating adhesive is preferably 18 seconds or less, more preferably 15 seconds or less, even more preferably 12 seconds or less, even more preferably 11 seconds or less, and still even more preferably 10 seconds or less.

[0121] In one embodiment of the bonding method using a high-frequency heating adhesive according to this embodiment, it is preferable that the frequency of the high frequency applied to the high-frequency heating adhesive in the above step is 3 MHz or more and 30 GHz or less. In one embodiment of the bonding method using a high-frequency heating adhesive according to this embodiment, it is also preferable that the applied high frequency is in the range of 3 MHz or more and 300 MHz or less, or in the range of 300 MHz or more and 30 GHz or less. When the applied high frequency is in the range of 3 MHz or more and 300 MHz or less, specifically, the industrial frequency bands 13.56 MHz, 27.12 MHz, or 40.68 MHz allocated by the International Telecommunication Union are also used in the manufacturing method and bonding method by high-frequency heating according to this embodiment. When the applied high frequency is in the range of 300 MHz or more and 30 GHz or less, specifically, the industrial frequency band 2.45 GHz allocated by the International Telecommunication Union is also used in the manufacturing method and bonding method by high-frequency heating according to this embodiment.

[0122] A method for manufacturing a structure by bonding it to an adherend includes, for example, the following steps:

[0123] When manufacturing a structure by bonding one or more adherends to the high-frequency heating adhesive according to this embodiment, the method for manufacturing the structure according to this embodiment includes the steps of: placing the high-frequency heating adhesive according to this embodiment on one or more adherends; and applying high frequency to the high-frequency heating adhesive to bond the one or more adherends. The conditions for the applied high frequency can be, for example, the conditions described above.

[0124] When manufacturing a structure by bonding two or more adherends to the high-frequency heating adhesive according to this embodiment, the method for manufacturing the structure according to this embodiment includes the steps of: placing the high-frequency heating adhesive according to this embodiment between the two or more adherends; and applying high frequency to the high-frequency heating adhesive to bond the two or more adherends. In this case as well, the conditions for the applied high frequency can be, for example, the conditions described above.

[0125] Here, the heat generation of filler (B) is not limited to dielectric heating alone. For example, when layered phosphate is used, heat can be generated by a dielectric heating device, but it is not limited to dielectric heating alone. In the following description, we will take as an example the case in which a structure is manufactured by bonding two or more adherends to the high-frequency heating adhesive according to this embodiment by applying a high-frequency electric field using a dielectric heating device.

[0126] In the manufacturing method of the structure according to this embodiment, it is preferable to place two or more adherends and a high-frequency heating adhesive between the electrodes of a dielectric heating device, and to apply a high-frequency electric field while applying pressure to the two or more adherends and the high-frequency heating adhesive with the electrodes. By applying a high-frequency electric field while applying pressure with the electrodes in this way, the structure can be manufactured in a shorter time. In this specification, "dielectric heating device" may sometimes be referred to as "high-frequency dielectric heating device."

[0127] According to the manufacturing method using the high-frequency heating adhesive of this embodiment, a dielectric heating device can be used to locally heat only predetermined areas from the outside. Therefore, even when the adherend is a large and complex three-dimensional structure or a thick and complex three-dimensional structure, and even when high dimensional accuracy is required, the manufacturing method using the high-frequency heating adhesive of this embodiment is effective.

[0128] The following describes an example of a method for manufacturing a structure according to this embodiment, in which two or more adherends are bonded together using the high-frequency heating adhesive according to this embodiment. However, the present invention is not limited to this embodiment.

[0129] An adhesive bonding method according to one aspect of this embodiment includes the following steps P1 and P2.

[0130] ·Process P1 Step P1 is a step of placing the high-frequency heating adhesive according to this embodiment between two or more adherends. When manufacturing a laminate as a structure according to this embodiment, in step P1, for example, adherends and high-frequency heating adhesives are arranged alternately to laminate two or more adherends via the high-frequency heating adhesive.

[0131] It is preferable to sandwich the high-frequency heating adhesive between the adherends so that they can be bonded together. The high-frequency heating adhesive may be sandwiched between a part of the adherends, between multiple locations, or across the entire surface between the adherends. From the viewpoint of improving the bonding strength between the adherends, it is preferable to sandwich the high-frequency heating adhesive over the entire bonding surface between the adherends. Furthermore, one embodiment of sandwiching the high-frequency heating adhesive between adherends is to arrange the high-frequency heating adhesive in a frame shape along the outer circumference of the adhesive surface between adherends and sandwich it between them. By arranging the high-frequency heating adhesive in a frame shape in this way, the adhesive strength between adherends can be obtained, and the structure can be made lighter compared to when the high-frequency heating adhesive is placed over the entire adhesive surface. Furthermore, in one embodiment in which a high-frequency heating adhesive is sandwiched between a portion of the adherends, the amount of high-frequency heating adhesive used can be reduced or its size can be made smaller, thus shortening the high-frequency heating treatment time compared to when the high-frequency heating adhesive is placed over the entire adhesive surface.

[0132] ·Process P2 Step P2 is a step in which a high-frequency electric field is applied to a high-frequency heating adhesive placed between the adherends in step P1 to bond two or more adherends. In one embodiment, the frequency of the applied high-frequency electric field is 3 MHz or more and 300 MHz or less. For example, a high-frequency electric field can be applied to the high-frequency heating adhesive by using a dielectric heating device.

[0133] <Dielectric heating device> Figure 3 shows a schematic diagram illustrating the high-frequency dielectric heating treatment using the high-frequency heating adhesive and dielectric heating device according to this embodiment. The dielectric heating device 50 shown in Figure 3 comprises 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 positioned facing each other. The first high-frequency electric field application electrode 51 and the second high-frequency electric field application electrode 52 have a press mechanism. The press mechanism of 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 allows the first adherend 110, the high-frequency heating adhesive 1A, and the second adherend 120 to be subjected to pressure treatment 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 pressurizing two or more adherends and the high-frequency heating adhesive placed between the electrodes.

[0134] When the first high-frequency electric field application electrode 51 and the second high-frequency electric field application electrode 52 constitute a pair of parallel plate electrodes, this type of electrode arrangement is sometimes referred to as the parallel plate type. It is also preferable to use a parallel-plate type high-frequency dielectric heating device for applying a high-frequency electric field. With a parallel-plate type high-frequency dielectric heating device, the high-frequency electric field penetrates the high-frequency heating adhesive located between the electrodes, so the entire high-frequency heating adhesive can be heated, and the adherend and the high-frequency heating adhesive can be bonded in a short time. Furthermore, when manufacturing laminates as structural components, it is preferable to use a parallel-plate type high-frequency dielectric heating device.

[0135] 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 for applying a high-frequency electric field with a frequency of approximately 13.56 MHz, 27.12 MHz, or 40.68 MHz, for example. As shown in Figure 3, the dielectric heating device 50 performs dielectric heating treatment via a high-frequency heating adhesive 1A sandwiched between the first adherend 110 and the second adherend 120. Furthermore, in addition to dielectric heating treatment, the dielectric heating device 50 adheres the first adherend 110 and the second adherend 120 by pressurizing treatment using the first high-frequency electric field application electrode 51 and the second high-frequency electric field application electrode 52. Alternatively, two or more adherends may be bonded by, for example, only by the pressure exerted by the high-frequency heating adhesive and the weight of the adherends themselves, without pressurizing treatment.

[0136] 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 heating adhesive 1A absorbs the high-frequency energy. As a result, the thermoplastic resin component in the high-frequency heating adhesive 1A melts, and the first adherend 110 and the second adherend 120 can be firmly bonded even with a short processing time.

[0137] 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 filler (B) dispersed in the adhesive component of the high-frequency heating adhesive 1A absorbs the high-frequency energy. Furthermore, the filler (B) functions as a heat source, and the heat generated by the filler (B) melts the thermoplastic resin component, so that even with a short processing time, the first adherend 110 and the second adherend 120 can ultimately be firmly bonded together.

[0138] Since the electrodes of the dielectric heating device 50 (first high-frequency electric field application electrode 51 and second high-frequency electric field application electrode 52) have a press mechanism, the dielectric heating device 50 also functions as a press device. Therefore, the first adherend 110 and the second adherend 120 can be bonded more firmly by applying pressure in the compression direction by the first high-frequency electric field application electrode 51 and the second high-frequency electric field application electrode 52, and by heating and melting the high-frequency heating adhesive 1A. In the description of the manufacturing method of the structure, the manufacturing of the structure 100 shown in Figure 3 is given as an example, but the present invention is not limited to this example.

[0139] <High-frequency electric field heating conditions> The high-frequency dielectric heating conditions can be changed as appropriate, but even when a high-frequency electric field is applied, it is preferable to adopt the aforementioned conditions for high-frequency output, high-frequency application time, and high-frequency frequency.

[0140] When applying a high-frequency electric field while pressurizing, the initial setting of the pressure applied to the high-frequency 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 still more preferably 50 kPa or more. When applying a high-frequency electric field while pressurizing, the pressing pressure when applying the high frequency 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, as the initial setting value of the pressure applied to the high-frequency heating adhesive. Here, the area that serves as the reference for the initial pressure setting applied to the high-frequency heating adhesive is the smallest area among the areas of the electrode and the adherend when viewed from above.

[0141] [Variations of the Embodiment] The present invention is not limited to the embodiments described above. The present invention may include modifications and improvements to the extent that they can achieve the objectives of the present invention.

[0142] The high-frequency heating treatment is not limited to the dielectric heating apparatus with electrodes arranged opposite each other as described in the above embodiment, but a grid electrode type high-frequency dielectric heating apparatus may also be used. The grid electrode type high-frequency dielectric heating apparatus has a grid electrode in which electrodes of first polarity and electrodes of second polarity, which are opposite in polarity to the electrodes of first polarity, are alternately arranged on the same plane at regular intervals. In the figure, for the sake of simplification, an example is shown using a dielectric heating apparatus with electrodes arranged opposite each other.

[0143] Furthermore, the high-frequency heating treatment is not limited to dielectric heating devices; in addition to dielectric heating devices, heating devices capable of heating by applying high-frequency waves may also be used. [Examples]

[0144] The present invention will be described in more detail below with reference to examples. The present invention is not limited to these examples.

[0145] [Manufacturing of adhesives for high-frequency heating] The high-frequency heating adhesives for each example were prepared according to the following procedure.

[0146] <Examples 1, 2, 3 and Comparative Examples 1, 2, 3> For the preparation of a high-frequency heating adhesive, thermoplastic resin (A) and filler (B) were weighed by volume in the proportions shown in Table 1.

[0147] Next, the thermoplastic resin (A) and filler (B) were pre-mixed. The pre-mixed material of thermoplastic resin (A) and filler (B) was supplied to the hopper of a 30 mmφ twin-screw extruder, the cylinder and die were heated to a predetermined temperature, and the pre-mixed material was melt-kneaded. After the melt-kneaded material was cooled, granular pellets were produced by cutting the material.

[0148] Next, the prepared granular pellets were fed into the hopper of a single-screw extruder equipped with a T-die, the cylinder and die were heated to a predetermined temperature, the film-like molten mixture was extruded from the T-die, and the mixture was cooled with a cooling roll to produce 400 μm thick sheet-like high-frequency heating adhesives (high-frequency heating adhesive sheets) according to the examples and comparative examples.

[0149] The thermoplastic resin (A) and filler (B) shown in Table 1 are described below.

[0150] (Thermoplastic resin (A)) (A1) r-PP: Polypropylene resin (manufactured by Prime Polymer Co., Ltd., product name "Prime PolyPro F-744NP").

[0151] (Filler (B)) (B1)Zr(PO4)2: Zirconium phosphate (manufactured by Daiichi Rare Elements Chemical Industry Co., Ltd., product name "CSZP-1", two-dimensional layered structure). (B2)Zr(PO4)2: Zirconium phosphate (manufactured by Daiichi Rare Elements Chemical Industry Co., Ltd., product name "CZP-100", two-dimensional layered structure). (B3) ZnO: Zinc oxide (manufactured by Hakusui Tech Co., Ltd., product name "DW-4", amorphous form) (B4) ZnO: Zinc oxide (crushed product of (B3) above)

[0152] The volume-average particle diameter of filler (B) was determined by measuring the particle size distribution of filler (B) using a laser diffraction particle size distribution analyzer (Malvern Panalytical, product name "Mastersizer 3000"), and calculating the volume-average particle diameter from the results of this particle size distribution measurement in accordance with JIS Z 8819-2:2019.

[0153] [Evaluation of physical properties of adhesives for high-frequency heating] The following evaluations were performed on each of the high-frequency heating adhesives that were fabricated.

[0154] <Temperature evaluation when high frequency is applied> Two glass fiber reinforced polypropylene resin sheets (25 mm long, 100 mm wide, 1.5 mm thick) were prepared as the adherends. The prepared high-frequency heating adhesive (adhesive sheet) was cut to dimensions of 25 mm long and 12.5 mm wide. The cut adhesive sheet was placed between the two adherends and laminated.

[0155] As described above, the laminated adherends and adhesive sheets were fixed between the two electrodes of a high-frequency dielectric heating device (Yamamoto Viniter Co., Ltd., product name "YRP-400T-A"). Next, with the adherends fixed, an electric field was applied under the following high-frequency electric field application conditions to bond the adhesive sheets to the adherends. The temperature of the adhesive sheet at the time of bonding was measured using a thermographic camera (FLIR Systems Japan Co., Ltd., product name "FLIR T860"), and the application time from the reference time and the temperature of the adhesive sheet were plotted. The pressing pressure during high-frequency electric field application is the initial setting value for the pressure applied to the adhesive sheet. The reference time is defined as the point when the temperature of the adhesive sheet reaches 50°C or exceeds 50°C. The reference time is defined as the temperature T0, and the temperature of the adhesive sheet is measured every 10 seconds from the reference time. 1、 T2, T3, and T4 were plotted. Then, the temperature rise rates for each were calculated using the aforementioned formulas (F1), (F2), (F3), and (F4).

[0156] (High-frequency electric field application conditions) Frequency: 40.68MHz Output: 100W Application time: Maximum 60 seconds Compression pressure: 0.5 MPa

[0157] <Adhesion Evaluation> Test specimens were prepared under the same conditions as those used for the temperature evaluation during high-frequency application described above. However, the application time was set to 10 seconds from the start of application, with the start time being defined as 0 seconds, rather than the reference time mentioned above. The obtained test specimens were left to stand for 24 hours in a 23°C, 50%RH environment, and then the tensile shear force (unit: MPa) as the adhesive strength at 23°C was measured using a universal tensile testing machine (Instron 5581, manufactured by Instron). The tensile shear force was measured in accordance with JIS K 6850:1999, with a tensile speed of 10 mm / min.

[0158] [Table 1]

[0159] [Table 2]

[0160] The reference temperature T0 is between 50°C and 60°C, exhibiting a certain range, which is due to the instantaneous rise in temperature in less than one second after the application of the high-frequency electric field.

[0161] In Comparative Example 1, the high-frequency heating adhesive sheet had a low temperature in the initial stages of high-frequency application, but the temperature increased as the high-frequency application continued. In Comparative Example 2, the high-frequency heating adhesive sheet also had a low temperature in the initial stages of high-frequency application, but the temperature of the high-frequency heating adhesive sheet in Comparative Example 2 did not rise easily even with continuous high-frequency application. In both Comparative Example 1 and Comparative Example 2, the high-frequency heating adhesive sheets did not adhere to the adherend after a high-frequency application time of 10 seconds from the start of application. In Comparative Example 3, the temperature was also low in the initial stages of high-frequency application, and therefore, it did not adhere to the adherend after a high-frequency application time of 10 seconds from the start of application.

[0162] In contrast, the high-frequency heating adhesive sheets of each embodiment exhibit a lower temperature rise rate in each section compared to the high-frequency heating adhesive sheet of Comparative Example 1. Furthermore, the high-frequency heating adhesive sheets of each embodiment achieve sufficient adhesive strength with the adherend even when the high-frequency application time from the start of application is only 10 seconds. For example, in Comparative Example 1, an adhesive strength of approximately 12 MPa can be obtained by increasing the output to 200 W or extending the application time to 20 seconds. This demonstrates that, compared to the comparative example, the high-frequency heating adhesives of each embodiment suppress the temperature rise of the adhesive even when high-frequency is continuously applied, enabling adhesion to the adherend with low power and a short time.

[0163] Referring to Figure 4, we see a graph where the horizontal axis represents the application time and the vertical axis represents the temperature of the high-frequency heating adhesive. In Figure 4, E1 and E2 correspond to Example 1 and Example 2, respectively, and C1 and C2 correspond to Comparative Example 1 and Comparative Example 2, respectively. Comparative Example 3 is omitted from the graph shown in Figure 4. As shown in Figure 4, the high-frequency heating adhesive sheets of Example 1 and Example 2 show a smaller temperature rise from 10 seconds after the application time compared to the high-frequency heating adhesive sheets of Comparative Example 1 and Comparative Example 2.

[0164] From the results above, it was confirmed that the high-frequency heating adhesive according to this embodiment can firmly adhere to the adherend while suppressing overheating. Furthermore, based on the above results, the high-frequency heating adhesive according to this embodiment suppresses the temperature rise of the high-frequency heating adhesive even when high frequency is continuously applied, and enables adhesion to the adherend with low power and in a short time. Therefore, it is expected to have the effect of reducing the power consumption required for adhesion to the adherend. [Explanation of Symbols]

[0165] 10,20...adhesive layer, 11...first surface, 21...second surface, 30...base material, 40...intermediate layer, 100...structure, 1A, 1B, 1C...adhesive for high frequency heating, 50...dielectric heating device, 51... Electrode (first high frequency electric field applying electrode), 52... Electrode (second high frequency electric field applying electrode), 53... High frequency power source, 110... Adherent (first adherend), 120... Adherent (second adherend).

Claims

1. A high-frequency heating adhesive, The aforementioned high-frequency heating adhesive is A thermoplastic resin (A) and a filler (B) that generates heat when high-frequency energy is applied, It contains, A high frequency of 40.68 MHz and an output of 100 W is applied, and the time when the temperature of the high-frequency heating adhesive reaches 50°C from the start of application of the high frequency is defined as the reference time, and the time when the high frequency is applied for 10 seconds from the reference time is defined as the first application time, and the temperature of the high-frequency heating adhesive at the first application time is defined as T １ The second application time is defined as the time when the high frequency is applied for 20 seconds from the reference time, and the temperature of the high-frequency heating adhesive at the second application time is defined as T ２ In that case, Said T １ The temperature is 80°C or higher. The temperature rise rate Tr1 of the high-frequency heating adhesive, expressed by the following formula (F1) between the first application time and the second application time, is 20% or less. Adhesive for high-frequency heating. Tr1(%)={(T ２ -T １ ) / T １ }×100 ・・・(F1)

2. In the high-frequency heating adhesive according to claim 1, The temperature of the high-frequency heating adhesive at the aforementioned reference time is T ０ In this case, the temperature rise rate Tr0, expressed by the following formula (F2), between the reference time and the first application time, is 30% or more. Adhesive for high-frequency heating. Tr0={(T １ -T ０ ) / T ０ }×100 …(F2)

3. In the high-frequency heating adhesive according to claim 1 or claim 2, The high frequency and output of the aforementioned frequency are applied, and the point in time when the high frequency has been applied for 30 seconds from the reference time is defined as the third application time, and the temperature of the high-frequency heating adhesive at the third application time is defined as T ３ The fourth application time is defined as the point in time when the high frequency is applied for 40 seconds from the reference time, and the temperature of the high-frequency heating adhesive at the fourth application time is defined as T ４ In that case, The temperature rise rate Tr2 of the high-frequency heating adhesive, expressed by the following formula (F3), between the second application time and the third application time, is 15% or less. The temperature rise rate Tr3 of the high-frequency heating adhesive, expressed by the following formula (F4), between the third application time and the fourth application time, is 15% or less. Adhesive for high-frequency heating. Tr2(%)={(T ３ -T ２ ) / T ２ }×100 ・・・(F3) Tr3(%)={(T ４ -T ３ ) / T ３ }×100 ・・・(F4)

4. In the high-frequency heating adhesive according to claim 1 or claim 2, The fourth application time is defined as the point in time when the aforementioned high frequency is applied for 40 seconds from the reference time, and the temperature of the high-frequency heating adhesive at the fourth application time is defined as T ４ In that case, the above T ４ The temperature is below 220°C. Adhesive for high-frequency heating.

5. In the high-frequency heating adhesive according to claim 1 or claim 2, The filler (B) is a layered phosphate. Adhesive for high-frequency heating.

6. In the high-frequency heating adhesive according to claim 5, The layered phosphate is zirconium phosphate. Adhesive for high-frequency heating.

7. In the high-frequency heating adhesive according to claim 5, The aforementioned layered phosphate does not support metal ions. Adhesive for high-frequency heating.

8. In the high-frequency heating adhesive according to claim 1 or claim 2, The content of the filler (B) is 8.0% by volume or more and 40.0% by volume or less relative to the total amount of the high-frequency heating adhesive. Adhesive for high-frequency heating.

9. In the high-frequency heating adhesive according to claim 1 or claim 2, The volume-average particle diameter of the filler (B) is 0.01 μm or more and 25.0 μm or less. The volume-average particle diameter is calculated in accordance with JIS Z 8819-2:2019 based on the results of the particle size distribution measurement of the filler (B) by laser diffraction and scattering. Adhesive for high-frequency heating.

10. In the high-frequency heating adhesive according to claim 1 or claim 2, The thermoplastic resin (A) is a polyolefin resin. Adhesive for high-frequency heating.

11. In the high-frequency heating adhesive according to claim 1 or claim 2, The content of the thermoplastic resin (A) is 60.0% by volume or more and 92.0% by volume or less relative to the total amount of the high-frequency heating adhesive. Adhesive for high-frequency heating.

12. In the high-frequency heating adhesive according to claim 1 or claim 2, The aforementioned high-frequency heating adhesive is a high-frequency heating adhesive sheet. Adhesive for high-frequency heating.

13. It is a structure, A high-frequency heating adhesive according to claim 1 or claim 2, The object to be adhered to, Equipped with, The adherend is bonded with the high-frequency heating adhesive. structure.

14. A bonding method using a high-frequency heating adhesive, The process involves applying high frequency to the high-frequency heating adhesive according to claim 1 or claim 2 to bond one or more adherends, The output of the aforementioned high frequency is 10W or more and 200W or less, and the application time of the aforementioned high frequency is 1 second or more and 20 seconds or less. Adhesion method.

15. A bonding method using a high-frequency heating adhesive as described in claim 14, The frequency of the aforementioned high-frequency is 3 MHz or higher and 30 GHz or lower. Adhesion method.

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