WO2024063029A1

WO2024063029A1 - Foam adhesive sheet, and method for manufacturing structure

Info

Publication number: WO2024063029A1
Application number: PCT/JP2023/033787
Authority: WO
Inventors: 純子小谷; 信之神田; 優菜鈴木; 健太郎星; 菜穂前田; 泉長谷川; 信哉島田
Original assignee: 大日本印刷株式会社
Priority date: 2022-09-20
Filing date: 2023-09-15
Publication date: 2024-03-28
Also published as: JP2024043866A

Abstract

The present disclosure provides a foam adhesive sheet having an adhesive layer, the adhesive layer containing a thermosetting adhesive and a foaming agent, wherein when a displacement was measured through the thermochemical analysis by applying a compressive load and elevating temperature at a predetermined rate, the sum of the initial thickness of the foam adhesive sheet and the amount of displacement at a predetermined temperature of 160 °C to 200 °C (exclusive of 200 °C) is 100% to 308% with respect to a gap setting value of 100%.

Description

Method for manufacturing foam adhesive sheet and structure

This disclosure relates to a foamable adhesive sheet and a method for manufacturing a structure using the same.

Adhesives for bonding members together are used in various fields, and many bonding methods are known.

For example,

Patent Documents

1 and 2 disclose adhesive sheets containing a foaming agent (foamable adhesive sheets). As a method of using a foamable adhesive sheet, for example, a method is known in which a foamable adhesive sheet is placed between members, and then the foamable adhesive sheet is foamed and cured by heating to bond the members together.

Such foamable adhesive sheets are required to have foaming properties to fill the gaps between components, and adhesive properties to bond the components together.

Japanese Patent Application Publication No. 2000-53944 Patent No. 6223477

However, when foaming and curing a foamable adhesive sheet by heating, both foaming and curing occur, so it is difficult to maintain a balance between foaming and curing, resulting in a decrease in foaming ratio and adhesive strength. There's a problem. As described above, it has been difficult to balance the expansion ratio and adhesive strength, and it has been difficult to obtain desired foaming characteristics and adhesive characteristics.

The present disclosure has been made in view of the above circumstances, and provides a foamable adhesive sheet and a structure using the foamable adhesive sheet, which is suitable for a predetermined gap and can obtain excellent foaming properties and adhesive properties. The main purpose is to provide a manufacturing method for.

One embodiment of the present disclosure is a foamable adhesive sheet having an adhesive layer, wherein the adhesive layer contains a thermosetting adhesive and a foaming agent, and in the foamable adhesive sheet, thermomechanical measurement The initial thickness of the foamable adhesive sheet and the amount of displacement at a predetermined temperature of 160 ° C or more and less than 200 ° C. Provided is a foamable adhesive sheet in which the total of the following is 100% or more and 308% or less with respect to the gap setting value of 100%.

Another embodiment of the present disclosure includes a step of arranging a foamable adhesive sheet having an adhesive layer between a first member and a second member, and a step of foaming and curing the foamable adhesive sheet by heating. a bonding step of bonding a member and the second member, wherein the adhesive layer contains a thermosetting adhesive and a foaming agent, and the foamable adhesive sheet includes: , by thermomechanical measurement, the initial thickness of the foamable adhesive sheet when applying a compressive load, increasing the temperature at a predetermined temperature increase rate, and measuring the displacement, and at a predetermined temperature of 160 ° C or more and less than 200 ° C. The total displacement amount is 100% or more and 308% or less with respect to the gap setting value of 100%, and the gap setting value is between the first member and the second member. Provided is a method for manufacturing a structure in which the distance of the gap after arranging the .

Another embodiment of the present disclosure includes a step of arranging a foamable adhesive sheet having an adhesive layer between a first member and a second member, and a step of foaming and curing the foamable adhesive sheet by heating. a bonding step of bonding a member and the second member, wherein the adhesive layer contains a thermosetting adhesive and a foaming agent, and the heating temperature in the bonding step is is 150°C or more and less than 200°C, and when the foamable adhesive sheet is heated to the heating temperature at a predetermined heating rate by applying a compressive load and the displacement is measured by thermomechanical measurement. The sum of the initial thickness of the foamable adhesive sheet and the amount of displacement is set to be 121% or more and 168% or less with respect to the gap setting value of 100%, and the gap setting value is A method for manufacturing a structure is provided, in which the distance of a gap after the foamable adhesive sheet is placed between one member and the second member is provided.

The present disclosure can provide a foamable adhesive sheet and a method for manufacturing a structure using the foamable adhesive sheet, which can obtain excellent foaming properties and adhesive properties suitable for a predetermined gap.

FIG. 1 is a schematic cross-sectional view illustrating a foamable adhesive sheet in the present disclosure. FIG. 1 is a schematic cross-sectional view illustrating a foamable adhesive sheet in the present disclosure. FIG. 1 is a schematic cross-sectional view illustrating a foamable adhesive sheet in the present disclosure. 1 is a graph illustrating a TMA curve for a foamable adhesive sheet. FIG. 1 is a schematic cross-sectional view illustrating a foamable adhesive sheet according to the present disclosure. FIG. 3 is a process diagram illustrating a method for manufacturing a structure according to the present disclosure. 1 is a graph illustrating a TMA curve for a foamable adhesive sheet.

Embodiments of the present disclosure will be described below with reference to the drawings and the like. However, the present disclosure can be implemented in many different ways, and should not be construed as being limited to the description of the embodiments exemplified below. Further, in order to make the explanation clearer, the drawings may schematically represent the width, thickness, shape, etc. of each part compared to the actual form, but this is just an example and does not limit the interpretation of the present disclosure. do not. In addition, in this specification and each figure, the same elements as those described above with respect to the previously shown figures are denoted by the same reference numerals, and detailed explanations may be omitted as appropriate.

In this specification, when expressing a mode in which another member is placed on top of a certain member, when it is simply expressed as "above" or "below", unless otherwise specified, it means that the member is in contact with a certain member. This includes both cases in which another member is placed directly above or below a certain member, and cases in which another member is placed above or below a certain member via another member. In addition, in this specification, when expressing a mode in which another member is arranged on the surface of a certain member, when it is simply expressed as "on the surface side" or "on the surface", unless otherwise specified, This includes both a case in which another member is placed directly above or directly below a certain member, and a case in which another member is placed above or below a certain member via another member.

Furthermore, in this specification, the term "sheet" also includes a member called a "film." Furthermore, the term "film" also includes a member called a "sheet." Moreover, the numerical range in this specification is a range of average values.

In order to fill the gaps between members and join the members together, the foamable adhesive sheet must have foaming characteristics such that the thickness of the foamable adhesive sheet after foaming and curing is at least as thick as the gap between the members. be. However, as described above, in foamable adhesive sheets, it is difficult to balance the expansion ratio and adhesive strength. Therefore, it can be said that there is still room for investigation regarding foaming characteristics and adhesive characteristics suitable for the intended gap.

Conventionally, the foaming properties of a foamable adhesive sheet have been evaluated, for example, by the expansion ratio of the foamable adhesive sheet. Generally, the foaming ratio of a foamable adhesive sheet refers to the foaming ratio when the foamable adhesive sheet is foamed and cured in a state where no external pressure is applied to the foamable adhesive sheet.

On the other hand, when bonding components together using a foam adhesive sheet, the foam adhesive sheet is sandwiched between the components and the foam is cured. The sheet will be foamed and hardened. Therefore, the conditions for measuring the expansion ratio of a foamable adhesive sheet and the actual foaming and curing conditions for a foamable adhesive sheet are significantly different.

On the other hand, when measuring the foaming characteristics of a foamable adhesive sheet by thermomechanical measurement (TMA), the foamable adhesive sheet is heated under a compressive load, and the displacement due to thermal expansion of the foamable adhesive sheet is measured. Measure. In this case, the foamable adhesive sheet is foamed and cured while a certain degree of compressive load is applied to the foamed adhesive sheet. Therefore, the measurement conditions for the thermomechanical analysis can be closer to the actual foaming and curing conditions of the foamable adhesive sheet, compared to the conditions for measuring the expansion ratio of the conventional foamable adhesive sheet. Therefore, it is thought that thermomechanical measurements can provide measured values that reflect the foaming and curing behavior of the foamable adhesive sheet.

Therefore, the inventors of the present disclosure focused on the foaming properties of a foamable adhesive sheet measured by thermomechanical measurement, and as a result of intensive studies on the foaming properties and adhesive properties of a foamable adhesive sheet, It has been found that there is a correlation between the amount of displacement when measuring the foaming characteristics of a foamable adhesive sheet and the adhesive strength of the foamable adhesive sheet after foaming and curing. If the total of the initial thickness of the foamable adhesive sheet and the amount of displacement measured by thermomechanical measurement is within a predetermined range for the target gap, then It was found that the adhesive strength was increased. The present disclosure is based on such knowledge.

Hereinafter, the method for manufacturing the foamable adhesive sheet and structure in the present disclosure will be described in detail.

A. Foamable Adhesive Sheet The foamable adhesive sheet in the present disclosure is a foamable adhesive sheet having an adhesive layer, the adhesive layer containing a thermosetting adhesive and a foaming agent, and the foamable adhesive sheet , the initial thickness of the foamable adhesive sheet and a predetermined temperature of 160 ° C or more and less than 200 ° C The sum of the amount of displacement at and is 100% or more and 308% or less with respect to the gap setting value of 100%.

The foamable adhesive sheet in the present disclosure will be explained with reference to the drawings. 1 to 3 are schematic cross-sectional views illustrating a foamable adhesive sheet according to the present disclosure. The foamable adhesive sheet 10 in FIG. 1 has an adhesive layer 1. The foamable adhesive sheet 10 shown in FIG. The foamable adhesive sheet 10 in FIG. 2 has a first adhesive layer 1a and a second adhesive layer 1b. The foamable adhesive sheet 10 in FIG. 3 has a first adhesive layer 1a, a base material 2, and a second adhesive layer 1b in this order. Moreover, the adhesive layer 1, the first adhesive layer 1a, and the second adhesive layer 1b all contain a thermosetting adhesive and a foaming agent.

Figure 4 shows the temperature on the horizontal axis and the displacement on the vertical axis when the foamable adhesive sheet was measured by thermomechanical measurement (TMA) by applying a compressive load and increasing the temperature at a predetermined temperature increase rate. It is a graph illustrating a TMA curve with an axis. In the foamable adhesive sheet of the present disclosure, the sum of the initial thickness of the foamable adhesive sheet and the amount of displacement at a predetermined temperature in the TMA curve as shown in FIG. 4 is within a predetermined range with respect to the gap setting value. be.

In the foamable adhesive sheet of the present disclosure, the sum of the initial thickness of the foamable adhesive sheet and the amount of displacement at a predetermined temperature measured by thermomechanical measurement is within a predetermined range with respect to the gap setting value. As a result, excellent foaming and adhesion properties can be obtained that are suitable for the gap settings. Therefore, it is possible to obtain a foamable adhesive sheet that is optimal for filling gaps between members and joining members together, with respect to the gap setting value.

Hereinafter, each structure of the foamable adhesive sheet in the present disclosure will be explained.

1. Characteristics In the foamable adhesive sheet of the present disclosure, the initial thickness of the foamable adhesive sheet and 160° C. were determined by thermomechanical measurement when a compressive load was applied, the temperature was raised at a predetermined temperature increase rate, and the displacement was measured. The total amount of displacement at a predetermined temperature of 200° C. or more is 100% or more and 308% or less with respect to the gap setting value of 100%. The total of the initial thickness of the foamable adhesive sheet and the above displacement amount is preferably 112% or more and 308% or less, more preferably 138% or more and 308% or less, with respect to the gap setting value of 100%. . When the sum of the initial thickness of the foamable adhesive sheet and the displacement amount is within the above range, foaming characteristics and adhesive characteristics suitable for the gap setting value can be obtained.

Here, the thermomechanical measurement is performed by the following method. First, a foam adhesive sheet is punched out using a jig with a diameter of 4 mm to prepare a sample. Next, the sample is placed in an aluminum container with a diameter of 5 mm, and an aluminum plate with a diameter of 4 mm is placed on top of the sample. Next, thermomechanical measurement is performed under the conditions of temperature: 25° C. or more and 250° C. or less, heating rate: 20° C./min, load: 10 mN, and compression mode, and displacement due to expansion or contraction of the sample is measured. Then, the amount of displacement at a predetermined temperature is determined. As the thermomechanical measuring device, for example, a thermomechanical analyzer TMA7100 manufactured by Hitachi High-Tech Science Co., Ltd. is used.

Note that the amount of displacement at a predetermined temperature refers to the amount of displacement accompanying expansion when the predetermined temperature is reached, with the amount of displacement at 25° C. being 0 in the TMA curve. The unit of displacement is "μm".

Furthermore, when determining the amount of displacement at a predetermined temperature, the predetermined temperature is any temperature between 160°C and below 200°C. This is because when the predetermined temperature is within the above range, a foamable adhesive sheet with good heat resistance can be obtained. Therefore, it can be applied to applications that require heat resistance similar to that of automobile engines. Further, if the predetermined temperature is lower than the above range, the amount of displacement at the predetermined temperature tends to be small. Therefore, adhesive strength may decrease. In this case, interfacial destruction may easily occur between the adhesive sheet and the member after foaming and curing. Here, in a microcapsule type foaming agent, a thermal expansion agent such as a hydrocarbon is encapsulated inside a shell made of resin. In the case of a microcapsule type foaming agent, when heated, the resin constituting the shell softens and the pressure of a thermal expansion agent such as a hydrocarbon increases, causing the microcapsule type foaming agent to expand. As the shell becomes thinner due to expansion, if heating is continued, the thermal expansion agent will escape from the microcapsule foaming agent, causing the microcapsule foaming agent to shrink. Therefore, in the case of a microcapsule type foaming agent, in the TMA curve, the amount of displacement tends to decrease after reaching the maximum amount of displacement. Therefore, if the predetermined temperature is higher than the above range, the amount of displacement at the predetermined temperature will become small, and as a result, the adhesive strength may decrease. Therefore, in the present disclosure, the above-mentioned predetermined temperature is an arbitrary temperature of 160°C or more and less than 200°C.

In the foamable adhesive sheet, the amount of displacement can be controlled, for example, by adjusting the particle size and content of the foaming agent. For example, when the particle size of the blowing agent is large, the above displacement amount tends to be large. On the other hand, when the particle size of the blowing agent is small, the amount of displacement tends to be small. Further, for example, when the content of the blowing agent is large, the above displacement amount tends to become large. On the other hand, when the content of the blowing agent is small, the above displacement amount tends to be small.

In addition, the initial thickness of the foamable adhesive sheet is the thickness of the foamable adhesive sheet before foaming, and the thickness of the foamable adhesive sheet at room temperature after setting the foamable adhesive sheet sample in a thermomechanical measuring device. Refers to thickness. Specifically, as described above, first, a sample is produced by punching out a foamable adhesive sheet using a jig of 4 mm in diameter. Next, the sample is placed in an aluminum container with a diameter of 5 mm, and an aluminum plate with a diameter of 4 mm is placed on top of the sample. In this state, the expansion and compression probe of the thermomechanical measurement device is brought into contact with the sample under a load of 100 mN, and the thickness after the aluminum plate and the sample are brought into sufficiently smooth contact is defined as the initial thickness of the foamable adhesive sheet. In addition, when the foamable adhesive sheet has a separator, the initial thickness of the foamable adhesive sheet refers to the thickness of the foamable adhesive sheet excluding the separator. The unit of the initial thickness of the foamable adhesive sheet is "μm".

Further, the above-mentioned gap setting value is preferably, for example, 100 μm or more and 500 μm or less, and more preferably 200 μm or more and 400 μm or less. The present disclosure is suitable when the gap setting is relatively small as described above. Note that the definition of the gap setting value will be described later. The unit of the gap setting value is "μm".

Furthermore, it is preferable that the foamable adhesive sheet of the present disclosure has a high adhesive strength after foaming and curing. The shear strength (adhesive strength) based on JIS K6850:1999 corresponding to ISO 4587 may be, for example, 1.50 MPa or more, 1.80 MPa or more, or 2.10 MPa or more at 23°C. Furthermore, the above shear strength (adhesive strength) may be, for example, 0.50 MPa or more, 0.75 MPa or more, or 1.00 MPa or more at 130°C. For example, in a high-strength acrylic foam adhesive tape that does not require heating, the shear strength (adhesive strength) is about 1 MPa or more and 2 MPa or less at room temperature, and it does not have heat resistance at 200°C. Therefore, if the above shear strength (adhesive strength) is in the above range at 23°C, it has an advantage in terms of strength. Furthermore, if the above shear strength (adhesive strength) is in the above range at 130°C, it can be applied to applications that require heat resistance around an automobile engine or similar.

Furthermore, the foamable adhesive sheet in the present disclosure preferably has high electrical insulation properties after foaming and curing. After the foamable adhesive sheet is foamed and cured, the dielectric breakdown voltage based on JIS C2107:2011 corresponding to IEC 60454-2 is preferably, for example, 3 kV or more, and more preferably 5 kV or more. When the dielectric breakdown voltage is within the above range, it becomes possible to prevent rust and to be applied around copper wires. Further, after the foamable adhesive sheet is foamed and cured, the thermal conductivity is preferably, for example, 0.1 W/mK or more, and more preferably 0.15 W/mK or more. When the thermal conductivity is within the above range, the parts can be made smaller and the curing reaction during heating can be promoted.

2. Adhesive Layer The adhesive layer in the present disclosure contains a thermosetting adhesive and a foaming agent.

(1) Material (a) Foaming agent The foaming agent in the present disclosure is a foaming agent that causes a foaming reaction due to heat. As the foaming agent, a foaming agent that is generally used in the adhesive layer of a foamable adhesive sheet can be used.

The foaming initiation temperature of the foaming agent is equal to or higher than the softening temperature of the main ingredient of a thermosetting adhesive such as an epoxy resin, and below the activation temperature of the curing reaction of the main ingredient of a thermosetting adhesive such as an epoxy resin. It is preferable that there be. The foaming start temperature of the foaming agent is, for example, 70°C or higher, and may be 100°C or higher. If the foaming start temperature is too low, foaming will start early, foaming will occur while the flexibility and fluidity of the resin component is low, and uniform foaming may be difficult to produce. On the other hand, the foaming start temperature of the foaming agent is, for example, 210° C. or lower. If the foaming start temperature is too high, the resin component may deteriorate. Specifically, the foaming start temperature of the foaming agent is 70°C or more and 210°C or less, and may be 100°C or more and 210°C or less.

Note that the softening temperature of the main ingredient of a thermosetting adhesive such as an epoxy resin is measured using the ring and ball softening temperature test method specified in JIS K7234:1986.

Examples of the foaming agent include microcapsule foaming agents. It is preferable that the microcapsule type foaming agent has a thermal expansion agent such as a hydrocarbon as a core and a resin such as an acrylonitrile copolymer as a shell.

Furthermore, as the blowing agent, for example, an organic blowing agent or an inorganic blowing agent may be used. Examples of organic blowing agents include azo blowing agents such as azodicarbonamide (ADCA), azobisformamide, and azobisisobutyronitrile, fluorinated alkane blowing agents such as trichloromonofluoromethane, and paratoluenesulfonyl hydrazide. Hydrazine blowing agents, semicarbazide blowing agents such as p-toluenesulfonyl semicarbazide, triazole blowing agents such as 5-morpholyl-1,2,3,4-thiatriazole, N, such as N,N-dinitrosoterephthalamide, etc. - Examples include nitroso blowing agents. On the other hand, examples of inorganic blowing agents include ammonium carbonate, ammonium hydrogen carbonate, ammonium nitrite, ammonium borohydride, and azides.

The blowing agents may be used alone or in combination of two or more.

The average particle diameter of the blowing agent may be, for example, 10 μm or more, 13 μm or more, or 17 μm or more. Further, the average particle diameter of the foaming agent is preferably equal to or less than the thickness of the adhesive layer, and may be, for example, 44 μm or less, 30 μm or less, or 24 μm or less. Specifically, the average particle size of the foaming agent may be 10 μm or more and 44 μm or less, 13 μm or more and 30 μm or less, or 17 μm or more and 24 μm or less.

Note that the average particle size of the blowing agent is the particle size at 50% of the integrated value in the particle size distribution determined by laser diffraction scattering method. Furthermore, when measuring the average particle size of the foaming agent, the adhesive layer is dissolved in a solvent and the foaming agent is separated. The solvent is not particularly limited as long as it is capable of dissolving components other than the foaming agent contained in the adhesive layer, and is appropriately selected depending on the type of thermosetting adhesive contained in the adhesive layer. . For example, a solvent used in the adhesive composition used to form the adhesive layer can be used. Specifically, methyl ethyl ketone, ethyl acetate, toluene, etc. can be used.

The foaming ratio of the foaming agent at the maximum foaming temperature is, for example, 1.5 times or more, and may be 3 times or more. On the other hand, the foaming ratio of the foaming agent at the maximum foaming temperature is, for example, 15 times or less, and may be 10 times or less. Specifically, the foaming ratio of the foaming agent at the maximum foaming temperature is 1.5 times or more and 15 times or less, and may be 3 times or more and 10 times or less.

The content of the foaming agent is, for example, 0.5 parts by mass or more, may be 2 parts by mass or more, and may be 3 parts by mass or more when the resin component contained in the adhesive layer is 100 parts by mass. The amount may be 4 parts by mass or more, or 5 parts by mass or more. On the other hand, the content of the foaming agent is, for example, 25 parts by mass or less, may be 20 parts by mass or less, or may be 15 parts by mass or less, based on 100 parts by mass of the resin component contained in the adhesive layer. . If the content of the foaming agent is too large, the content of the thermosetting adhesive will be relatively small, which may reduce the adhesive strength after foaming and curing. Specifically, the content of the foaming agent is 0.5 parts by mass or more and 25 parts by mass or less, and 2 parts by mass or more and 25 parts by mass or less, when the resin component contained in the adhesive layer is 100 parts by mass. It may be 3 parts by mass or more and 20 parts by mass or less, 4 parts by mass or more and 15 parts by mass or less, or 5 parts by mass or more and 15 parts by mass or less.

(b) Thermosetting Adhesive As the thermosetting adhesive in the present disclosure, a thermosetting adhesive generally used for the adhesive layer of a foamable adhesive sheet can be used. The thermosetting adhesive can be applied even when the member is not transparent, such as a metal member.

Examples of thermosetting adhesives include epoxy resin adhesives, acrylic resin adhesives, phenolic resin adhesives, unsaturated polyester resin adhesives, alkyd resin adhesives, and urethane resin adhesives. , thermosetting polyimide resin adhesives, and the like.

Among these, the thermosetting adhesive is preferably an epoxy resin adhesive. That is, the thermosetting adhesive preferably contains an epoxy resin and a curing agent. In general, epoxy resin adhesives have excellent mechanical strength, heat resistance, insulation, chemical resistance, etc., have low curing shrinkage, and can be used in a wide range of applications.

Hereinafter, a case where the thermosetting adhesive is an epoxy resin adhesive will be explained by giving an example.

(i) Epoxy resin The epoxy resin in the present disclosure is a compound that has at least one epoxy group or glycidyl group and is cured by causing a crosslinking polymerization reaction when used in combination with a curing agent. Epoxy resins also include monomers having at least one epoxy group or glycidyl group.

Examples of the epoxy resin include aromatic epoxy resins, aliphatic epoxy resins, alicyclic epoxy resins, and heterocyclic epoxy resins. Specific examples of epoxy resins include bisphenol type epoxy resins such as bisphenol A type epoxy resin and bisphenol F type epoxy resin, bisphenol A novolac type epoxy resin, novolac type epoxy resin such as cresol novolac type epoxy resin, urethane modified epoxy resin, etc. Examples include modified epoxy resins such as rubber modified epoxy resins. In addition, other specific examples include biphenyl-type epoxy resin, stilbene-type epoxy resin, triphenolmethane-type epoxy resin, alkyl-modified triphenolmethane-type epoxy resin, triazine nucleus-containing epoxy resin, dicyclopentadiene-modified phenol-type epoxy resin, Examples include naphthalene type epoxy resin, glycol type epoxy resin, and pentaerythritol type epoxy resin. The number of epoxy resins may be one, or two or more.

The bisphenol A epoxy resin can exist in a liquid state at room temperature or in a solid state at room temperature, depending on the number of repeating units in the bisphenol skeleton. A bisphenol A type epoxy resin whose main chain has a bisphenol skeleton of, for example, 2 or more and 10 or less is solid at room temperature. Particularly, bisphenol A type epoxy resin is preferable since it can improve heat resistance.

The epoxy resin may be a monofunctional epoxy resin, a bifunctional epoxy resin, a trifunctional epoxy resin, or a tetrafunctional or higher functional epoxy resin.

(ii) Acrylic resin In the present disclosure, when the thermosetting adhesive is an epoxy resin adhesive, the adhesive layer may further contain an acrylic resin that is compatible with the epoxy resin. Acrylic resin is a resin that is compatible with epoxy resin. Since acrylic resin is compatible with epoxy resin, it is easy to improve the toughness of the adhesive layer. As a result, the adhesiveness after foaming and curing can be improved. Furthermore, the acrylic resin acts as a compatibilizer for the foaming agent (for example, a foaming agent whose shell is made of acrylonitrile copolymer resin), and is thought to improve adhesiveness after foaming and curing by uniformly dispersing and foaming. . In addition, the flexibility of the acrylic resin is exhibited, and it is possible to improve the adhesion to the base material after foaming and hardening and the cracking resistance after foaming and hardening. Furthermore, since the acrylic resin is compatible with the epoxy resin, the hardness of the surface of the adhesive layer can be kept high. On the other hand, if the acrylic resin is incompatible with the epoxy resin, a flexible portion will be formed on the surface of the adhesive layer, making the interface with the first member and the second member less slippery, reducing workability. There is.

The acrylic resin in the present disclosure is compatible with the epoxy resin. Here, the fact that the acrylic resin is compatible with the epoxy resin means that micron-sized islands occur when the cross section of the adhesive layer is observed using a scanning electron microscope (SEM) or a transmission electron microscope (TEM). Check that it is not. More specifically, it is preferable that the average particle size of the islands is 1 μm or less. Among these, the average particle size of the islands may be 0.5 μm or less, or 0.3 μm or less. The number of samples is preferably large, for example 100 or more. The area to be observed is in the range of 100 μm×100 μm, or in the case where the thickness of the adhesive layer is 100 μm or less, the area is in the range of thickness×100 μm.

The acrylic resin may have a polar group. Examples of the polar group include an epoxy group, a hydroxyl group, a carboxyl group, a nitrile group, and an amide group.

The acrylic resin is a homopolymer of acrylic ester monomers, may be a mixed component containing two or more of the above homopolymers, or is a copolymer of two or more acrylic ester monomers. , or a copolymer. Moreover, the acrylic resin may be a mixed component of the above-mentioned homopolymer and the above-mentioned copolymer. The acrylic acid ester monomer "acrylic acid" also includes the concept of methacrylic acid. Specifically, the acrylic resin may be a mixture of a methacrylate polymer and an acrylate polymer, or may be an acrylic acid ester polymer such as acrylate-acrylate, methacrylate-methacrylate, or methacrylate-acrylate. . Among these, the acrylic resin preferably contains a copolymer of two or more types of acrylic ester monomers ((meth)acrylic ester copolymer).

Examples of the monomer components constituting the (meth)acrylic acid ester copolymer include the monomer components described in JP-A-2014-065889. The monomer component may have the above-mentioned polar group. Examples of the (meth)acrylic acid ester copolymer include ethyl acrylate-butyl acrylate-acrylonitrile copolymer, ethyl acrylate-acrylonitrile copolymer, and butyl acrylate-acrylonitrile copolymer. Note that "acrylic acid" such as methyl acrylate and ethyl acrylate also includes "methacrylic acid" such as methyl methacrylate and ethyl methacrylate.

The above (meth)acrylic acid ester copolymer is preferably a block copolymer, and more preferably an acrylic block copolymer such as a methacrylate-acrylate copolymer. Examples of the (meth)acrylate constituting the acrylic block copolymer include methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate, and acrylic acid. Examples include benzidyl. These "acrylic acids" also include "methacrylic acids."

Specific examples of the methacrylate-acrylate copolymer include acrylic copolymers such as methyl methacrylate-butyl acrylate-methyl methacrylate (MMA-BA-MMA) copolymer. MMA-BA-MMA copolymers also include block copolymers of polymethyl methacrylate-polybutyl acrylate-polymethyl methacrylate (PMMA-PBA-PMMA).

The acrylic copolymer does not need to have a polar group, or may be a modified product in which the above-mentioned polar groups are partially introduced. Since the above-mentioned modified product is easily compatible with the epoxy resin, the adhesiveness is further improved.

Among them, the acrylic resin is a (meth)acrylic acid having a first polymer part having a glass transition temperature (Tg) of 10°C or lower and a second polymer part having a glass transition temperature (Tg) of 20°C or higher. Preferably, it is an ester copolymer. Such a (meth)acrylic acid ester copolymer has a first polymer portion that becomes a soft segment and a second polymer portion that becomes a hard segment. By adding such a copolymer, the adhesive layer has improved toughness after curing and can further increase adhesive strength.

The manifestation of the above effects can be estimated as follows. By using an acrylic resin that has both soft and hard segments, such as the above-mentioned (meth)acrylic acid ester copolymer, the hard segments contribute to heat resistance, and the soft segments contribute to toughness or flexibility. , an adhesive layer with good heat resistance, toughness, and flexibility can be obtained.

At least one of the first polymer portion and the second polymer portion contained in the (meth)acrylic acid ester copolymer has compatibility with the epoxy resin. If the first polymer portion is compatible with the epoxy resin, flexibility can be increased. Moreover, when the second polymeric part has compatibility with the epoxy resin, cohesiveness and toughness can be improved.

The above-mentioned (meth)acrylic acid ester copolymer is preferably a block copolymer, particularly ABA in which the compatible portion is polymer block A and the incompatible portion is polymer block B. Preferably, it is a block copolymer. Furthermore, the first polymer portion is an incompatible portion, the second polymer portion is a compatible portion, the first polymer portion is a polymer block B, and the second polymer portion is a polymer block A. -BA block copolymer is preferred.

Moreover, the above-mentioned (meth)acrylic acid ester copolymer may be a modified product in which the above-mentioned polar group is introduced into a part of the first polymer portion or the second polymer portion.

A specific example of the (meth)acrylic acid ester copolymer having the first polymer portion and the second polymer portion is the MMA-BA-MMA copolymer described above.

The content of the acrylic resin is, for example, 1 part by mass or more, may be 3 parts by mass or more, or even 5 parts by mass or more when the resin component contained in the adhesive layer is 100 parts by mass. The amount may be 7 parts by mass or more, or 10 parts by mass or more. If the content of the acrylic resin is too low, the adhesiveness after foaming and curing and the adhesiveness of the adhesive layer to the base material may decrease. On the other hand, the content of the acrylic resin is, for example, 60 parts by mass or less, may be 50 parts by mass or less, and may be 40 parts by mass or less, when the resin component contained in the adhesive layer is 100 parts by mass. The amount may be 35 parts by mass or less, or 30 parts by mass or less. If the content of acrylic resin is too large, the film strength may decrease.

Further, as described later, when the foamable adhesive sheet has a first adhesive layer and a second adhesive layer as adhesive layers, the content of acrylic resin in the first adhesive layer and the second adhesive layer is the same. may be different from each other.

(iii) Curing Agent As the curing agent in the present disclosure, a curing agent generally used in an epoxy resin-based adhesive can be used.

The curing agent is preferably solid at 23°C. A curing agent that is solid at 23°C can have a longer storage stability (pot life) compared to a curing agent that is liquid at 23°C. Further, the curing agent may be a latent curing agent. Further, the curing agent is usually a curing agent that causes a curing reaction due to heat. Moreover, one type of curing agent may be used alone, or two or more types may be used.

The reaction initiation temperature of the curing agent is, for example, 110°C or higher, and may be 130°C or higher. If the reaction initiation temperature is too low, the reaction will start early, and curing will occur with the resin component having low flexibility and fluidity, making it difficult to achieve uniform curing. On the other hand, the reaction initiation temperature of the curing agent is, for example, 200° C. or lower. If the reaction initiation temperature is too high, the resin component may deteriorate. In addition, when using a resin with high heat resistance, such as a phenol resin, in addition to the epoxy resin, the reaction initiation temperature of the curing agent may be, for example, 300 ° C. or lower, since the resin component is less likely to deteriorate. . Specifically, the reaction start temperature of the curing agent is 110°C or more and 300°C or less, may be 110°C or more and 200°C or less, or may be 130°C or more and 200°C or less. The reaction initiation temperature of the curing agent is determined by differential scanning calorimetry (DSC).

Specific examples of the curing agent include imidazole curing agents, phenol curing agents, amine curing agents, acid anhydride curing agents, isocyanate curing agents, and thiol curing agents.

Examples of imidazole-based curing agents include imidazole, 2-phenyl-4,5-dihydroxymethylimidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole, 2-methylimidazole, 2-ethylimidazole, 2-ethyl-4-methylimidazole, 2-isopropylimidazole, 2-phenylimidazole, carboxylates of imidazole compounds, and adducts with epoxy compounds. It is also preferable that imidazole-based curing agents have hydroxyl groups. As crystallization occurs through hydrogen bonds between hydroxyl groups, the reaction initiation temperature tends to be high.

Examples of phenolic curing agents include phenolic resins. Further, examples of the phenol resin include resol type phenol resin and novolak type phenol resin. From the viewpoint of adhesion to the substrate after foaming and curing, cracking resistance after foaming and curing, etc., a phenolic novolac resin having a Tg of 110° C. or less is particularly preferred. Furthermore, a phenolic curing agent and an imidazole curing agent may be used in combination. In that case, it is preferable to use an imidazole curing agent as a curing catalyst.

Examples of the amine curing agent include aliphatic amines, aromatic amines, alicyclic amines, and polyamide amines. Examples of aliphatic amines include diethylenetriamine (DETA), triethylenetetramine (TETA), metaxylylylene diamine (MXDA), and the like. Examples of aromatic amines include diaminodiphenylmethane (DDM), m-phenylenediamine (MPDA), and diaminodiphenylsulfone (DDS). Further, as the amine curing agent, a dicyandiamide curing agent such as dicyandiamide (DICY), an organic acid dihydrazide curing agent, an amine adduct curing agent, or a ketimine curing agent can be used.

Examples of acid anhydride curing agents include alicyclic acid anhydrides (liquid acid anhydrides) and aromatic acid anhydrides. Examples of the alicyclic acid anhydride include hexahydrophthalic anhydride (HHPA), methyltetrahydrophthalic anhydride (MTHPA), and the like. Examples of the aromatic acid anhydride include trimellitic anhydride (TMA), pyromellitic anhydride (PMDA), benzophenonetetracarboxylic acid (BTDA), and the like.

Examples of the isocyanate curing agent include block isocyanate.

Examples of the thiol curing agent include ester bond type thiol compounds, aliphatic ether bond type thiol compounds, and aromatic ether bond type thiol compounds.

Among these, it is preferable to use a curing agent other than an imidazole curing agent in combination with an imidazole curing agent. In that case, it is preferable to use an imidazole curing agent as a curing catalyst.

The content of the curing agent is, for example, 1 part by mass or more and 40 parts by mass or less, when the resin component contained in the adhesive layer is 100 parts by mass. For example, when using an imidazole-based curing agent as a main component, the content of the curing agent is, for example, 1 part by mass or more and 15 parts by mass or less, when the resin component contained in the adhesive layer is 100 parts by mass. It is preferable that On the other hand, when using a phenolic curing agent as the main component, the content of the curing agent is, for example, 5 parts by mass or more and 40 parts by mass or less, when the resin component contained in the adhesive layer is 100 parts by mass. It is preferable that Note that using an imidazole curing agent or a phenolic curing agent as a main component as a curing agent means that the mass proportion of the imidazole curing agent or phenol curing agent is the largest in the curing agent.

(c) Other components The adhesive layer in the present disclosure may contain only the above-mentioned epoxy resin and acrylic resin as resin components, for example, when the thermosetting adhesive is an epoxy resin adhesive, It may further contain other resins. Examples of other resins include urethane resins.

The total ratio of the epoxy resin and the acrylic resin to the resin component contained in the adhesive layer is, for example, 70% by mass or more, may be 80% by mass or more, may be 90% by mass or more, and may be 100% by mass. It may be %.

The content of the resin component in the adhesive layer is, for example, 60% by mass or more, or may be 70% by mass or more, 80% by mass or more, or may be 90% by mass or more.

The adhesive layer contains additives such as silane coupling agents, fillers, antioxidants, light stabilizers, ultraviolet absorbers, lubricants, plasticizers, antistatic agents, crosslinking agents, colorants, etc., as necessary. You may do so. Examples of the silane coupling agent include epoxy-based silane coupling agents. Examples of the filler include inorganic fillers such as calcium carbonate, aluminum hydroxide, magnesium hydroxide, antimony trioxide, zinc borate, molybdenum compounds, and titanium dioxide. Examples of the antioxidant include phenolic antioxidants and sulfur-based antioxidants.

(2) Adhesive layer The thickness of the adhesive layer is not particularly limited, but is preferably equal to or larger than the average particle size of the foaming agent. The thickness of the adhesive layer may be, for example, 10 μm or more and 200 μm or less, 15 μm or more and 150 μm or less, or 20 μm or more and 100 μm or less. If the adhesive layer is too thin, it may not be possible to obtain sufficient adhesion to the base material and adhesion after foaming and curing. Furthermore, if the adhesive layer is too thick, the surface quality may deteriorate.

Here, the thickness of the adhesive layer is measured from a cross section in the thickness direction of the foamable adhesive sheet observed by a transmission electron microscope (TEM), a scanning electron microscope (SEM), or a scanning transmission electron microscope (STEM). This value is the average value of the thickness of 10 randomly selected locations. Note that the same applies to the method of measuring the thickness of other layers included in the foamable adhesive sheet.

The adhesive layer may be a continuous layer or a discontinuous layer. Examples of the discontinuous layer include patterns such as stripes and dots. Further, the surface of the adhesive layer may have an uneven shape such as embossing.

The adhesive layer can be formed, for example, by applying an adhesive composition and removing the solvent. Examples of coating methods include roll coating, reverse roll coating, transfer roll coating, gravure coating, gravure reverse coating, comma coating, rod coating, blade coating, bar coating, wire bar coating, die coating, lip coating, dip coating, etc. can be mentioned.

The adhesive composition may or may not contain a solvent. Note that the term "solvent" as used herein has a broad meaning that includes not only a strict solvent (a solvent that dissolves a solute) but also a dispersion medium. Further, the solvent contained in the adhesive composition is evaporated and removed when the adhesive composition is applied and dried to form an adhesive layer.

The adhesive composition can be obtained by mixing the above-mentioned components, kneading and dispersing as necessary. For mixing and dispersing methods, common kneading and dispersing machines such as two-roll mills, three-roll mills, pebble mills, trom mills, Szegvari attritors, high-speed impeller dispersing machines, high-speed stone mills, high-speed impact mills, and despars are used. , high-speed mixer, ribbon blender, co-kneader, intensive mixer, tumbler, blender, desperser, homogenizer, and ultrasonic dispersion machine are applicable.

The foamable adhesive sheet in the present disclosure only needs to have an adhesive layer, for example, it may have only one adhesive layer, or it may have a first adhesive layer and a second adhesive layer as adhesive layers. It's okay. Further, when the foamable adhesive sheet according to the present disclosure has a first adhesive layer and a second adhesive layer as adhesive layers, it may have the first adhesive layer and the second adhesive layer in this order, and the first adhesive layer and the second adhesive layer may be provided in this order. The layer, the base material, and the second adhesive layer may be included in this order. When the base material is arranged between the first adhesive layer and the second adhesive layer, the handleability and workability of the foamable adhesive sheet can be improved. On the other hand, when the foamable adhesive sheet does not have a base material, the thickness of the entire foamable adhesive sheet can be reduced. Therefore, for example, the foamable adhesive sheet can be inserted into a narrow gap.

3. Base material The foamable adhesive sheet in the present disclosure has a first adhesive layer and a second adhesive layer as adhesive layers, and may have a base material between the first adhesive layer and the second adhesive layer. .

It is preferable that the base material has insulation properties. Further, the base material is preferably in the form of a sheet. The base material may have a single layer structure or a multilayer structure. Further, the base material may or may not have a porous structure inside.

Examples of the base material include resin base materials and nonwoven fabrics.

Examples of the resin contained in the resin base material include polyester resin, polycarbonate, polyarylate, polyurethane, polyamide, polyamide resin, polyimide resin, polysulfone resin, polyetherketone resin, polyphenylene sulfide (PPS), modified polyphenylene oxide, and the like. Examples of the polyester resin include polyethylene terephthalate (PET), polybutylene terephthalate, polyethylene naphthalate (PEN), and aromatic polyester. Examples of the polyamide resin include polyetheramide. Examples of the polyimide resin include polyimide, polyetherimide, and polyamideimide. Examples of the polysulfone resin include polysulfone and polyethersulfone. Examples of the polyetherketone resin include polyetherketone and polyetheretherketone. The glass transition temperature of the resin is, for example, 80°C or higher, may be 140°C or higher, or may be 200°C or higher. Furthermore, liquid crystal polymer (LCP) may be used as the resin.

Examples of the nonwoven fabric include nonwoven fabrics containing fibers such as cellulose fibers, polyester fibers, nylon fibers, aramid fibers, polyphenylene sulfide fibers, liquid crystal polymer fibers, glass fibers, metal fibers, and carbon fibers.

The base material may be surface-treated to improve adhesion with the adhesive layer.

The thickness of the base material is not particularly limited, and may be, for example, 2 μm or more and 200 μm or less, 5 μm or more and 100 μm or less, or 9 μm or more and 50 μm or less.

4. Other configurations In addition to the adhesive layer and base material described above, the foamable adhesive sheet in the present disclosure may have other configurations as necessary.

(1) Intermediate layer The foamable adhesive sheet in the present disclosure may have a first intermediate layer between the base material and the first adhesive layer. Further, the foamable adhesive sheet in the present disclosure may have a second intermediate layer between the base material and the second adhesive layer. By arranging the first intermediate layer and the second intermediate layer, it is possible to improve the adhesion of the first adhesive layer and the second adhesive layer to the base material. Furthermore, by arranging the first intermediate layer and the second intermediate layer, for example, when the foam adhesive sheet is bent, stress applied to the bent part can be alleviated, and when the foam adhesive sheet is cut, the stress applied to the bent part can be alleviated. The stress applied to the cut portion can be alleviated. As a result, it is possible to suppress lifting and peeling of the first adhesive layer and the second adhesive layer from the base material when the foamable adhesive sheet is bent or cut.

For example, in the foamable adhesive sheet 10 shown in FIG. Layer 3b is arranged. In addition, although the foamable adhesive sheet 10 has both the first intermediate layer 3a and the second intermediate layer 3b in FIG. 5, it may have only either one.

The foamable adhesive sheet only needs to have at least one of the first intermediate layer and the second intermediate layer, for example, only the first intermediate layer disposed between the base material and the first adhesive layer. It may have only the second intermediate layer disposed between the base material and the second adhesive layer, or it may have only the second intermediate layer disposed between the base material and the first adhesive layer, and the base material and the first intermediate layer disposed between the base material and the first adhesive layer. and a second intermediate layer disposed between the second adhesive layer. Among these, it is preferable that the first intermediate layer is disposed between the base material and the first adhesive layer, and that the second intermediate layer is disposed between the base material and the second adhesive layer.

The material included in the first intermediate layer and the second intermediate layer may be any material that can enhance the adhesion between the base material and the first adhesive layer or the second adhesive layer, and can relieve stress. It is not particularly limited, and is appropriately selected depending on the materials of the base material, the first adhesive layer, the second adhesive layer, and the like. Examples include polyester, polyvinyl chloride, polyvinyl acetate, polyurethane, polymers obtained by copolymerizing at least two thereof, crosslinked products thereof, and mixtures thereof.

The crosslinked product is a crosslinked product obtained by crosslinking the above resin with a curing agent. Examples of the curing agent include isocyanate curing agents.

Among these, it is preferable that the first intermediate layer and the second intermediate layer contain a crosslinked resin. Note that crosslinked resin refers to one that does not melt even at high temperatures. This makes it possible to improve adhesive strength at high temperatures, that is, heat resistance.

The thickness of the first intermediate layer and the thickness of the second intermediate layer are not particularly limited, but are, for example, 0.1 μm or more, may be 0.5 μm or more, or may be 1 μm or more. If the first intermediate layer or the second intermediate layer is too thin, the effect of suppressing the peeling of the first adhesive layer or the second adhesive layer from the base material during bending or cutting of the foamable adhesive sheet will not be achieved sufficiently. there is a possibility. On the other hand, the thickness of the first intermediate layer and the thickness of the second intermediate layer are, for example, 4 μm or less, and may be 3.5 μm or less. The first intermediate layer and the second intermediate layer themselves usually do not have high heat resistance, so if the first intermediate layer or the second intermediate layer is too thick, the heat resistance (adhesion strength at high temperatures) may decrease. There is. Specifically, the thickness of the first intermediate layer and the thickness of the second intermediate layer are 0.1 μm or more and 4 μm or less, and may be 0.5 μm or more and 4 μm or less, and 0.5 μm or more and 3.5 μm or less. The thickness may be 1 μm or more and 3.5 μm or less.

The first intermediate layer and the second intermediate layer can be formed, for example, by applying a resin composition and removing the solvent. Examples of coating methods include roll coating, reverse roll coating, transfer roll coating, gravure coating, gravure reverse coating, comma coating, rod coating, blade coating, bar coating, wire bar coating, die coating, lip coating, and dip coating. Can be mentioned.

(2) Separator The foamable adhesive sheet in the present disclosure may have a first separator on the side of the first adhesive layer opposite to the second adhesive layer. Further, the foamable adhesive sheet in the present disclosure may have a second separator on the side of the second adhesive layer opposite to the first adhesive layer.

The first separator and the second separator are not particularly limited as long as they can be peeled off from the first adhesive layer and the second adhesive layer, and have sufficient strength to protect the first adhesive layer and the second adhesive layer. be able to. Examples of the first separator and the second separator include a release film, release paper, and the like. Further, the first separator and the second separator may have a single layer structure or a multilayer structure.

Examples of the single-layer separator include fluororesin films.

Further, as a separator with a multilayer structure, for example, a laminate having a release layer on one or both sides of a base layer can be mentioned. Examples of the base material layer include resin films such as polypropylene, polyethylene, and polyethylene terephthalate, and papers such as high-quality paper, coated paper, and impregnated paper. The material for the release layer is not particularly limited as long as it has release properties, and examples include silicone compounds, organic compound-modified silicone compounds, fluorine compounds, aminoalkyd compounds, melamine compounds, acrylic compounds, polyester compounds, and long-lasting materials. Examples include chain alkyl compounds. These compounds may be of emulsion type, solvent type or non-solvent type.

5. Foamable Adhesive Sheet The thickness of the foamable adhesive sheet in the present disclosure is, for example, 10 μm or more, and may be 20 μm or more. On the other hand, the thickness of the foamable adhesive sheet is, for example, 1000 μm or less, and may be 200 μm or less. Specifically, the thickness of the foamable adhesive sheet is 10 μm or more and 1000 μm or less, and may be 20 μm or more and 200 μm or less. The thickness of the foamable adhesive sheet here and the initial thickness of the foamable adhesive sheet described above are different.

The use of the foamable adhesive sheet in the present disclosure is not particularly limited. The foamable adhesive sheet according to the present disclosure can be used, for example, to bond two members together by placing the foamable adhesive sheet between two members and then foaming and curing the foamable adhesive sheet by heating. Can be done. Specifically, the foamable adhesive sheet according to the present disclosure is used for adhering a coil and a stator in a motor, and for adhering a rotor and a permanent magnet in an embedded magnet type motor.

The method for manufacturing the foamable adhesive sheet in the present disclosure is not particularly limited.

For example, when the foamable adhesive sheet has only one adhesive layer and no base material, the adhesive layer is formed by applying an adhesive composition to one side of the separator and drying it. There are several methods. Thereafter, the separator may be peeled off.

For example, when the foamable adhesive sheet has a first adhesive layer and a second adhesive layer as adhesive layers and does not have a base material between the first adhesive layer and the second adhesive layer, it is possible to applying and drying an adhesive composition to form a first adhesive layer on the separator, and applying an adhesive composition to form a second adhesive layer on the second separator; and drying to form a second adhesive layer, and a method of laminating a laminate of the first separator and the first adhesive layer and a laminate of the second separator and the second adhesive layer. After that, the first separator and the second separator may be peeled off.

For example, when the foamable adhesive sheet has a first adhesive layer, a base material, and a second adhesive layer in this order, by applying and drying the adhesive composition on both sides of the base material, Mention may be made of methods for forming the first adhesive layer and the second adhesive layer. The first adhesive layer and the second adhesive layer may be formed sequentially or simultaneously. Alternatively, for example, the first adhesive layer may be formed by applying and drying the adhesive composition on one side of the base material, and the first adhesive layer may be formed by applying and drying the adhesive composition on one side of the separator. Another example is a method of forming two adhesive layers and laminating the second adhesive layer and a separator on the other side of the base material.

B. Method for manufacturing a structure The method for manufacturing a structure in the present disclosure has two embodiments. Each embodiment will be described below.

1. First Embodiment A first embodiment of the method for manufacturing a structure according to the present disclosure includes a step of arranging a foamable adhesive sheet having an adhesive layer between a first member and a second member, and a step of arranging a foamable adhesive sheet having an adhesive layer. a bonding step of foaming and curing by heating and bonding the first member and the second member, the adhesive layer comprising a thermosetting adhesive, a foaming agent, and a foaming agent. In the foamable adhesive sheet, the initial thickness of the foamable adhesive sheet is determined by thermomechanical measurement when a compressive load is applied, the temperature is raised at a predetermined temperature increase rate, and the displacement is measured. The total amount of displacement at a predetermined temperature of 100% or more and less than 200°C is 100% or more and 308% or less with respect to 100% of the gap setting value, and the gap setting value is This is the distance of the gap after the foamable adhesive sheet is placed between the two members.

FIGS. 6(a) to 6(b) are process diagrams illustrating the method for manufacturing the structure of this embodiment. First, as shown in FIG. 6(a), the foamable adhesive sheet 10 is placed between the first member 20a and the second member 20b. Next, as shown in FIG. 6(b), the adhesive layer of the foamable adhesive sheet 10 is foamed and cured by heating. The first member 20a and the second member 20b are adhered (joined) by the adhesive sheet 11 after foaming and hardening. Thereby, a structure 100 is obtained in which the adhesive sheet 11 is arranged between the first member 20a and the second member 20b.

Furthermore, in the foamable adhesive sheet of this embodiment, the sum of the initial thickness of the foamable adhesive sheet and the amount of displacement at a predetermined temperature in the TMA curve as shown in FIG. Within range.

The gap setting value is the distance of the gap after the foamable adhesive sheet is placed between the first member and the second member. For example, in FIG. 6A, the sum of the distances d1 and d2 of the gaps G1 and G2 after the foam adhesive sheet 10 is placed between the first member 20a and the second member 20b is the gap setting value.

In the method for manufacturing a structure of this embodiment, the above-mentioned foamable adhesive sheet is used. Therefore, excellent foaming and adhesion properties suitable for the gap settings can be obtained. Therefore, in order to fill the gaps between the members and join the members to each other, it is possible to select and use the foamable adhesive sheet that is most suitable for the gap setting value.

Hereinafter, the foamable adhesive sheet used in the method of manufacturing a structure of this embodiment and each step of the method of manufacturing a structure of this embodiment will be described.

(1) Foamable adhesive sheet In the foamable adhesive sheet used in this embodiment, displacement was measured by applying a compressive load and increasing the temperature at a predetermined temperature increase rate by thermomechanical measurement. At this time, the sum of the initial thickness of the foamable adhesive sheet and the amount of displacement at a predetermined temperature of 160° C. or more and less than 200° C. is within a predetermined range with respect to the gap setting value.

The foamable adhesive sheet is the same as the foamable adhesive sheet described above.

Note that in this embodiment, the gap setting value is the distance of the gap after the foamable adhesive sheet is placed between the first member and the second member.

(2) Arrangement step The arrangement step in this embodiment is a step of arranging a foamable adhesive sheet having an adhesive layer between the first member and the second member.

The method of arranging the foamable adhesive sheet between the first member and the second member is appropriately selected depending on the types of the first member and the second member. For example, a method in which a foam adhesive sheet is placed on one of the first member and the second member, and the other member is placed on the side of the foam adhesive sheet opposite to the first member; and a method of inserting a foam adhesive sheet into the gap between the second member, after placing the foam adhesive sheet in the hole, groove, etc. of the first member, foam adhesive in the hole, groove, etc. of the first member. Examples include a method of inserting a second member into the gap after the sheet is placed. For example, when the first member has holes or grooves and the second member is placed in the holes or grooves of the first member and is bonded, a foam adhesive sheet may be attached to the second member. After that, a second member with a foam adhesive sheet pasted in the hole or groove of the first member is placed. After the foam adhesive sheet is pasted in the hole or groove of the first member, the foam adhesive sheet is Examples include a method of arranging the second member in a hole or groove of the first member to which the second member is pasted.

The first and second members are appropriately selected depending on the application of the structure. The first and second members are preferably members that require adhesion and insulation. For example, motor parts are included. More specifically, the coil and stator of a motor, and the rotor and permanent magnet of an embedded magnet motor are included.

(3) Adhesion process The adhesion process in this embodiment is a process of foaming and curing the foamable adhesive sheet by heating and bonding the first member and the second member.

The heating temperature in the bonding process is the initial thickness of the foamable adhesive sheet when a compressive load is applied to the foamable adhesive sheet, the temperature is raised at a predetermined temperature increase rate, and the displacement is measured by thermomechanical measurement. It is preferable that the total amount including the amount of displacement at a predetermined temperature is set to be 100% or more and 308% or less, and preferably set to be 112% or more and 294% or less with respect to the gap setting value of 100%. It is more preferable that If the heating temperature is lower than the above range, the amount of displacement will be small, so foaming will be insufficient and adhesive strength may decrease. In this case, interfacial destruction may easily occur between the adhesive sheet after foaming and curing and the first member or the second member. Furthermore, as described above, in the case of microcapsule-type foaming agents, the amount of displacement tends to decrease after reaching the maximum amount of displacement in the TMA curve. Therefore, if the heating temperature is higher than the above range, the amount of displacement will become smaller after reaching the maximum amount of displacement, and as a result, the thickness of the adhesive layer during foaming cannot be maintained, and the adhesive strength may decrease. There is sex.

Specifically, the heating temperature is preferably 160°C or higher and 190°C or lower. When the heating temperature is within the above range, heat resistance can be improved. Therefore, it can be applied to applications that require heat resistance similar to that of automobile engines.

2. Second Embodiment A second embodiment of the method for manufacturing a structure according to the present disclosure includes a step of arranging a foamable adhesive sheet having an adhesive layer between a first member and a second member; a bonding step of foaming and curing by heating and bonding the first member and the second member, the adhesive layer comprising a thermosetting adhesive, a foaming agent, and a foaming agent. and the heating temperature in the bonding step is 150°C or more and less than 200°C, and in the foamable adhesive sheet, according to thermomechanical measurement, a compressive load is applied to the heating temperature at a predetermined temperature increase rate. Set so that the sum of the initial thickness of the foamable adhesive sheet and the amount of displacement is 121% or more and 168% or less with respect to the gap setting value of 100% when the temperature is increased to However, the gap setting value is the distance of the gap after the foamable adhesive sheet is placed between the first member and the second member.

FIG. 7 shows the time on the horizontal axis, when the foamable adhesive sheet was heated to a predetermined temperature at a predetermined temperature increase rate, and the displacement was measured by thermomechanical measurement (TMA). It is a graph illustrating a TMA curve with displacement amount as the vertical axis. In the method for manufacturing a structure of this embodiment, the heating temperature in the bonding step is 150°C or more and less than 200°C, and the initial thickness of the foamable adhesive sheet and the foamable adhesive sheet as shown in FIG. The sum of the amount of displacement in the TMA curve and the amount of displacement in the TMA curve is set so that it is within a predetermined range with respect to the gap setting value.

In the foamable adhesive sheet of this embodiment, the heating temperature in the bonding step is 150°C or more and less than 200°C, and the initial thickness of the foamable adhesive sheet and the foamable adhesive sheet are measured by thermomechanical measurement. By setting the sum together with the displacement amount to be within a predetermined range with respect to the gap setting value, excellent foaming properties and adhesive properties suitable for the gap setting value can be obtained. Therefore, the heating conditions in the bonding process can be optimized with respect to the gap setting value.

Conventionally, heating conditions during foam curing of a foamable adhesive sheet are set based on, for example, the foaming start temperature of the foaming agent, the maximum foaming temperature of the foaming agent, the curing start temperature of the adhesive, etc. For example, Patent Document 2 states that regarding the heating conditions, when the thermal foaming temperature (foaming start temperature) of the thermal foaming agent is T1 and the curing start temperature of the adhesive layer is T2, the relationship T1≦T2 is satisfied. Disclosed. However, when the inventors of the present disclosure studied the heating conditions during foaming and curing of a foamable adhesive sheet, it was found that the foaming start temperature of the foaming agent and the hardening start temperature of the adhesive layer are in a predetermined relationship. It was also found that the adhesive strength may decrease. Note that the foaming start temperature and maximum foaming temperature of the foaming agent are the foaming characteristics of the foaming agent alone, and cannot be said to be the foaming characteristics of the foamable adhesive sheet.

In contrast, in this embodiment, the heating conditions are set based on the initial thickness of the foamable adhesive sheet and the amount of displacement measured by thermomechanical measurement of the foamable adhesive sheet. As described above, the measurement conditions for the thermomechanical analysis can be made close to the actual foaming and curing conditions of the foamable adhesive sheet. Therefore, it is thought that thermomechanical measurements can provide measured values that reflect the foaming and curing behavior of the foamable adhesive sheet.

(1) Foamable adhesive sheet The foamable adhesive sheet used in this embodiment has an adhesive layer, and the adhesive layer contains a thermosetting adhesive and a foaming agent.

The adhesive layer in the foamable adhesive sheet is the same as the adhesive layer described in the section "A. Foamable adhesive sheet 2. Adhesive layer" above.

In addition, the other configurations of the foamable adhesive sheet are the same as those described in the section of "A. Foamable adhesive sheet" above.

(2) Arrangement step The arrangement step in this embodiment is a step of arranging a foamable adhesive sheet having an adhesive layer between the first member and the second member. The arrangement step and the first and second members are the same as those in the first embodiment.

In this embodiment, the heating temperature in the bonding process is 150°C or more and less than 200°C, and the foam adhesive sheet is heated to the heating temperature at a predetermined heating rate by applying a compressive load according to thermomechanical measurements. When the temperature is raised and the displacement is measured, the total of the initial thickness of the foamable adhesive sheet and the amount of displacement is set to be 121% or more and 168% or less with respect to the gap setting value of 100%. Among them, the heating temperature in the bonding step is 150°C or more and less than 200°C, and the total of the initial thickness of the foamable adhesive sheet and the above displacement is 149% or more with respect to the gap setting value of 100%. % or less. By setting the heating temperature within the above range, the heating conditions in the bonding process can be optimized with respect to the gap setting value.

Here, the thermomechanical measurement is performed by the following method. First, a foam adhesive sheet is punched out using a jig with a diameter of 4 mm to prepare a sample. Next, the sample is placed in an aluminum container with a diameter of 5 mm, and an aluminum plate with a diameter of 4 mm is placed on top of the sample. Next, thermomechanical measurements are performed under the conditions of temperature: 25° C. to a predetermined heating temperature, heating rate: 20° C./min, load: 10 mN, compression mode, and displacement due to expansion or contraction of the sample is measured. As the thermomechanical measuring device, for example, a thermomechanical analyzer TMA7100 manufactured by Hitachi High-Tech Science Co., Ltd. is used.

Further, the above-mentioned gap setting value is the same as the gap setting value described in the section of "A. Foamable adhesive sheet" above.

Note that the present disclosure is not limited to the above embodiments. The above-mentioned embodiments are illustrative, and any configuration that has substantially the same technical idea as the claims of the present disclosure and provides similar effects is the present invention. within the technical scope of the disclosure.

[Production Examples I to II]
First, an adhesive composition having the composition shown in Table 1 below was prepared. Further, details of each material listed in Table 1 are shown below.

・Acrylic resin: PMMA-PBuA-PMMA (acrylamide group in part), Tg: -20°C, 120°C, Mw: 150,000
・Epoxy resin A: Bisphenol A novolac type, solid at room temperature, softening temperature: 70°C, epoxy equivalent: 210g/eq, Mw: 1300, melt viscosity at 150°C: 0.5Pa・s
・Epoxy resin B: BPA phenoxy type, solid at room temperature, softening temperature: 110°C, epoxy equivalent: 8000g/eq, Mw: 50,000
・Epoxy resin C: bisphenol A type, liquid at room temperature, epoxy equivalent: 184 to 194 g/eq
・Epoxy resin D: Diaminodiphenylmethane type, high viscosity liquid, epoxy equivalent: 110 to 130 g/eq
・Epoxy resin E: silicone modification, epoxy equivalent: 1200 g/mol
・Curing agent 1: α-(hydroxy (or dihydroxy) phenylmethyl)-ω-hydropoly[biphenyl-4,4'-diylmethylene (hydroxy (or dihydroxy) phenylene methylene)]
・Curing agent 2: 2-phenyl-4,5-dihydroxymethylimidazole, average particle size: 3 μm, melting point: 230°C, reaction initiation temperature 145°C to 155°C, active area 155°C to 173°C (manufactured by Shikoku Kasei Kogyo Co., Ltd.) , 2PHZ-PW)

・Thermal foaming agent 1: thermally expandable microcapsules, average particle size 13 μm, expansion start temperature 123-133°C, maximum expansion temperature 168-178°C, core: hydrocarbon, shell: thermoplastic polymer ・Thermal foaming agent 2: Thermally expandable microcapsules, average particle size 21 μm, expansion start temperature 120-130°C, maximum expansion temperature 175-190°C, core: hydrocarbon, shell: thermoplastic polymer, silane coupling agent: 3-glycidoxypropyl Trimethoxysilane/Solvent: Methyl ethyl ketone

[Production Examples 1 to 9]
As a base material, polyethylene naphthalate (PEN film, manufactured by Toyobo Film Solutions Co., Ltd., Theonex Q51, thickness 25 μm) was prepared, with an intermediate layer having a thickness of 5 μm or less arranged on one surface. Next, the adhesive composition was applied to the surface of the substrate opposite to the intermediate layer using an applicator so that the thickness after drying was 45 μm. Thereafter, it was dried in an oven at 100° C. for 3 minutes to form a first adhesive layer.

Next, the adhesive composition was applied to the surface of the intermediate layer opposite to the base material using an applicator so that the thickness after drying was 45 μm. Thereafter, it was dried in an oven at 100° C. for 3 minutes to form a second adhesive layer.

Next, a release film (PET separator, made by Nipper Co., Ltd., PET50 ×1-J2, thickness 50 μm) was laminated. Thereby, a foamable adhesive sheet was obtained in which the first adhesive layer, the base material, the intermediate layer, the second adhesive layer, and the second separator were arranged in this order.

[Evaluation 1]
(1) Thermomechanical measurement (TMA)
As a thermomechanical measuring device, a thermomechanical analyzer TMA7100 manufactured by Hitachi High-Tech Science Co., Ltd. was used. First, a sample was prepared by punching out a foam adhesive sheet using a jig with a diameter of 4 mm. Next, the sample was placed in an aluminum container with a diameter of 5 mm with the second adhesive layer facing the bottom, and an aluminum plate with a diameter of 4 mm was placed on top of the sample. In this state, the expansion and compression probe of the thermomechanical measuring device was brought into contact with a load of 100 mN, and the thickness of the sample after sufficiently smooth contact between the aluminum plate and the sample was defined as the initial thickness of the foamable adhesive sheet. Next, thermomechanical measurements were performed under the conditions of temperature: 25° C. or higher and 250° C. or lower, heating rate: 20° C./min, load: 10 mN, and compression mode, and displacement due to expansion or contraction of the sample was measured. Then, the amount of displacement at each temperature was determined.

(2) Adhesive strength Two metal plates (cold rolled steel plate SPCC-SD) with a thickness of 1.6 mm, a width of 25 mm, and a length of 100 mm were prepared. Spacers were placed at one end of one of the metal plates at an interval of 15 mm. The thickness of the spacer is 300 μm (thickness of 5 layers of Kapton Tape P-221 manufactured by Nitto Denko Corporation) or 370 μm (thickness of 2 layers of Kapton Tape P-221 manufactured by Nitto Denko Corporation and fluororesin manufactured by Teraoka Manufacturing Co., Ltd.). The thickness was one layer of adhesive tape 8410). Further, the foam adhesive sheet was cut into a size of 12.5 mm x 25 mm. The foamable adhesive sheet was in a state with the separator removed. Next, a foam adhesive sheet was placed between the spacers, another metal plate was placed so that one tip overlapped with the other, and the sheet was fixed with a clip to obtain a test piece. Thereafter, the test piece was placed in a thermal oven (manufactured by Yamato Kagaku Co., Ltd., DN610) and heated to foam and harden the first adhesive layer and the second adhesive layer of the foamable adhesive sheet. At this time, the heating conditions were a temperature increase rate of 20°C/min and a heating temperature of 160°C, 180°C, and 200°C.

The shear strength (adhesive strength) of the heated test piece was measured using a tensile tester Tensilon RTF1350 (manufactured by A&D Co., Ltd.) in accordance with JIS K6850:1999. The measurement conditions were a tensile speed of 10 mm/min and a temperature of 23°C.

As shown in test numbers 1 to 9, in the foamable adhesive sheets of Production Examples 1 to 6, the initial thickness of the foamable adhesive sheet and a predetermined temperature of 160°C or higher and lower than 200°C, as measured by TMA. The total displacement amount was within a predetermined range with respect to the gap setting value. In the case of these foam adhesive sheets, from a comparison of test numbers 1 to 9 and test numbers 10 to 12, the adhesive strength increases when the heating temperature in the bonding process is 160°C or higher and 190°C or lower. I understand.

[Evaluation 2]
(1) Thermomechanical measurement (TMA)
As a thermomechanical measuring device, a thermomechanical analyzer TMA7100 manufactured by Hitachi High-Tech Science Co., Ltd. was used. First, a sample was prepared by punching out a foamable adhesive sheet using a jig with a diameter of 4 mm. Next, the sample was placed in an aluminum container with a diameter of 5 mm with the second adhesive layer facing the bottom, and an aluminum plate with a diameter of 4 mm was placed on top of the sample. In this state, the expansion and compression probe of the thermomechanical measuring device was brought into contact with a load of 100 mN, and the thickness of the sample after sufficiently smooth contact between the aluminum plate and the sample was defined as the initial thickness of the foamable adhesive sheet. Next, thermomechanical measurements were performed under the conditions of temperature: 25° C. to the final temperature, heating rate: 20° C./min, load: 10 mN, compression mode, and displacement due to expansion or contraction of the sample was measured. At this time, the temperatures reached were 150°C, 160°C, 180°C, 190°C, and 200°C.

(2) Adhesive strength Shear strength (adhesive strength) was measured in the same manner as in Evaluation 1. Regarding the heating conditions for the foamable adhesive sheet, the heating temperatures were 150°C, 160°C, 180°C, 190°C, and 200°C.

From Table 4, the heating temperature in the bonding process is 150°C or more and less than 200°C, and the total of the initial thickness of the foam adhesive sheet and the amount of displacement measured by TMA is relative to the gap setting value. It has been found that adhesive strength increases when the temperature falls within a predetermined range.

1... Adhesive layer 1a... First adhesive layer 1b... Second adhesive layer 2... Base material 3a... First intermediate layer 3b... Second intermediate layer 10... Foamable adhesive sheet 11... Adhesive sheet after foaming and curing 20a... First Member 20b... Second member 100... Structure

Claims

A foamable adhesive sheet having an adhesive layer,
The adhesive layer contains a thermosetting adhesive and a foaming agent,
In the foamable adhesive sheet, the initial thickness of the foamable adhesive sheet is determined by thermomechanical measurement when a compressive load is applied, the temperature is raised at a predetermined temperature increase rate, and the displacement is measured. A foamable adhesive sheet, wherein the total amount of displacement at a predetermined temperature of less than 100% is 100% or more and 308% or less with respect to a gap setting value of 100%.
The adhesive layer includes a first adhesive layer and a second adhesive layer,
The foamable adhesive sheet according to claim 1, comprising the first adhesive layer, the base material, and the second adhesive layer in this order.
a step of arranging a foam adhesive sheet having an adhesive layer between the first member and the second member;
an adhesion step of foaming and curing the foamable adhesive sheet by heating and adhering the first member and the second member;
A method for manufacturing a structure having:
The adhesive layer contains a thermosetting adhesive and a foaming agent,
In the foamable adhesive sheet, the initial thickness of the foamable adhesive sheet is determined by thermomechanical measurement when a compressive load is applied, the temperature is raised at a predetermined temperature increase rate, and the displacement is measured. The total amount of displacement at a predetermined temperature of less than 100% and 308% or less with respect to the gap setting value of 100%,
A method for manufacturing a structure, wherein the gap setting value is a gap distance after the foamable adhesive sheet is placed between the first member and the second member.
The method for manufacturing a structure according to claim 3, wherein the heating temperature in the bonding step is 160°C or more and 190°C or less.
a step of arranging a foam adhesive sheet having an adhesive layer between the first member and the second member;
an adhesion step of foaming and curing the foamable adhesive sheet by heating and adhering the first member and the second member;
A method for manufacturing a structure having:
The adhesive layer contains a thermosetting adhesive and a foaming agent,
The heating temperature in the adhesion step is 150° C. or more and less than 200° C., and the foamable adhesive sheet is heated to the heating temperature at a predetermined heating rate by applying a compressive load according to thermomechanical measurement. , when the displacement is measured, the total of the initial thickness of the foamable adhesive sheet and the amount of displacement is set to be 121% or more and 168% or less with respect to the gap setting value of 100%,
A method for manufacturing a structure, wherein the gap setting value is a gap distance after the foamable adhesive sheet is placed between the first member and the second member.
The method for manufacturing a structure according to claim 5, wherein the heating temperature in the bonding step is 160°C or more and 190°C or less.
The method for manufacturing a structure according to any one of claims 3 to 6, wherein the foamable adhesive sheet has a first adhesive layer and a second adhesive layer as the adhesive layers, and has the first adhesive layer, a substrate, and the second adhesive layer in this order.