Adhesive layer, laminate, curable composition, method for producing recycled product, and method for reducing adhesive strength

Abstract

The present disclosure relates to: an adhesive layer characterized by including a first adhesive layer and a second adhesive layer having a higher dielectric strength than the first adhesive layer, and by being used for electrical pulse peeling; a laminate including the adhesive layer; a curable composition for forming the adhesive layer; a method for producing a recycled product; and a method for reducing adhesive strength.

Description

Adhesive layer, laminate, curable composition, method for producing recycled product, and method for reducing adhesive strength

[0001] The present invention relates to adhesive layers for use in electric pulse peeling.

[0002] Communication terminal devices, home appliances, and other products that are no longer in use due to breakdowns or changes in their product life cycles are collected by businesses and then disassembled and dismantled for recycling or reuse. Traditionally, this work has often involved manual disassembly followed by physical dismantling using a crusher or similar. Recently, an electric pulse dismantling method has been reported (Patent Document 1), in which multiple electrodes are placed at spaced positions on the surface of an object where an insulator and a conductor are bonded or joined, and a voltage is applied between the electrodes to dismantle the object into an insulator and a conductor.

[0003] Japanese Patent Application Laid-Open No. 2020-069454

[0004] However, the method described in Patent Document 1 has the drawback that even if an electric pulse is applied, the adhesive strength of the bonded portion, i.e., the adhesive layer, may not be sufficiently reduced, making it difficult to disassemble.

[0005] The present invention has been made in view of the above problems, and a main object of the present invention is to provide an adhesive layer whose adhesive strength can be stably reduced by applying an electric pulse.

[0006] As a result of extensive research, the present inventors have found that by using adhesive layers with different dielectric strengths, it is possible to stably reduce adhesive strength by applying an electric pulse.

[0007] That is, the present disclosure provides an adhesive layer characterized by being used for electric pulse peeling, the adhesive layer including a first adhesive layer and a second adhesive layer having a higher dielectric strength than the first adhesive layer. The present disclosure also provides a laminate in which a first member and a second member are bonded via an adhesive layer, the adhesive layer including a first adhesive layer and a second adhesive layer having a higher dielectric strength than the first adhesive layer, the laminate characterized by being used for electric pulse peeling. Furthermore, the present disclosure provides a curable composition including a conductive material and a resin component, the curable composition including a first adhesive layer and a second adhesive layer having a higher dielectric strength than the first adhesive layer, the curable composition being used for forming the first adhesive layer of an adhesive layer used for electric pulse peeling. The present disclosure also provides a method for reducing adhesive strength, which includes a step of applying an electric pulse to a laminate in which a first member and a second member are bonded via an adhesive layer, and is characterized in that the adhesive layer includes a first adhesive layer and a second adhesive layer having a higher dielectric strength than the first adhesive layer, and a method for manufacturing a recycled product using the method for reducing adhesive strength.

[0008] According to the present disclosure, it is possible to provide an adhesive layer whose adhesive strength can be stably reduced by applying an electric pulse.

[0009] 1A is a schematic plan view illustrating an example of an adhesive layer according to the present disclosure, and FIG. 1B is a cross-sectional view taken along line A-A. 1A is a schematic plan view illustrating another example of an adhesive layer according to the present disclosure, and FIG. 1B is a cross-sectional view taken along line A-A. 1A is a schematic plan view illustrating another example of an adhesive layer according to the present disclosure, and FIG. 1B is a schematic plan view illustrating another example of an adhesive layer according to the present disclosure. 1B is a schematic cross-sectional view illustrating an example of a laminate according to the present disclosure. 1B is a schematic diagram illustrating an example of a high-voltage pulse generator used in the method for reducing adhesive strength according to the present disclosure. 1C is a circuit diagram illustrating an example of a high-voltage pulse generator used in reducing the adhesive strength of an adhesive layer according to the present disclosure. 1C is a schematic plan view illustrating a method for forming a laminate according to an example, and FIG. 1B is a schematic cross-sectional view illustrating a laminate according to an example. 1D is a graph illustrating voltage and current waveforms of electric pulses applied to laminates according to examples and comparative examples. 1E is an enlarged photograph of the adhesive layer of the laminate according to Example 1 after disassembly. 1F is an enlarged photograph of the adhesive layer of the laminate according to Example 2 after disassembly. 1 is a close-up photograph of the adhesive layer of the laminate of Example 3 after dismantling. FIG. 2 is a close-up photograph of the adhesive layer of the laminate of Example 4 after dismantling. FIG. 3 is a close-up photograph of the adhesive layer of the laminate of Example 5 after dismantling. FIG. 4 is a close-up photograph of the adhesive layer of the laminate of Example 6 after dismantling. FIG. 5 is a close-up photograph of the adhesive layer of the laminate of Example 7 after dismantling. FIG. 6 is a close-up photograph of the adhesive layer of the laminate of Example 8 after dismantling. FIG. 7 is a close-up photograph of the adhesive layer of the laminate of Comparative Example 1 after dismantling. FIG. 8 is a close-up photograph of the adhesive layer of the laminate of Comparative Example 2 after dismantling. FIG. 9 is a close-up photograph of the adhesive layer of the laminate of Comparative Example 3 after dismantling. FIG. 10 is a close-up photograph of the adhesive layer of the laminate of Comparative Example 4 after dismantling. FIG. 11 is a close-up photograph of the adhesive layer of the laminate of Comparative Example 5 after dismantling.

[0010] The present disclosure relates to an adhesive layer, a laminate including the adhesive layer, a curable composition used to form the adhesive layer, a method for producing a recycled product, and a method for reducing adhesive strength. The adhesive layer, laminate, curable composition, method for producing a recycled product, and method for reducing adhesive strength of the present disclosure are described in detail below.

[0011] A. Adhesive Layer First, the adhesive layer of the present disclosure will be described. The adhesive layer of the present disclosure has a first adhesive layer and a second adhesive layer having a higher dielectric strength than the first adhesive layer, and is characterized by being used for electric pulse peeling. By having the above structure of the adhesive layer, it is possible to stably reduce the adhesive strength of the adhesive layer after application of an electric pulse.

[0012] Although the reason why the adhesive layer having the above structure can stably reduce the adhesive strength of the adhesive layer after application of an electric pulse is not clear, it is presumed as follows. That is, by including a first adhesive layer and a second adhesive layer in the adhesive layer, an internal discharge can be preferentially generated in the first adhesive layer, which has a low dielectric strength, when an electric pulse is applied, and the adhesive strength of the adhesive layer can be reduced mainly around the first adhesive layer. Furthermore, as a method for forming the first adhesive layer and the second adhesive layer, a method of forming the adhesive layer in a pattern as described above can be adopted. Therefore, it is possible to form the first adhesive layer at a desired position, and it is possible to generate an internal discharge at a desired position when an electric pulse is applied.

[0013] A-1. Electrical Characteristics of the Adhesive Layer The adhesive layer of the present disclosure will be described with reference to FIG. 1. As illustrated in FIGS. 1(a) and 1(b), the adhesive layer 10 of the present disclosure includes a first adhesive layer 10a and a second adhesive layer 10b having a higher dielectric strength than the first adhesive layer 10a. By including the first adhesive layer 10a and the second adhesive layer 10b having different dielectric strengths, the discharge position within the adhesive layer 10 when an electric pulse is applied can be easily controlled to be within the first adhesive layer 10 having a lower dielectric strength, thereby making it possible to more stably reduce the adhesive strength of the adhesive layer 10 after the application of the electric pulse.

[0014] The absolute value of the difference between the dielectric strength of the first adhesive layer 10a and the dielectric strength of the second adhesive layer 10b may be any value that allows the adhesive layer 10 to stably reduce its adhesive strength after application of an electric pulse. The absolute value is preferably 0.1 kV / mm or more and 60 kV / mm or less, more preferably 10 kV / mm or more and 55 kV / mm or less, even more preferably 20 kV / mm or more and 50 kV / mm or less, particularly preferably 30 kV / mm or more and 50 kV / mm or less, and most preferably 40 kV / mm or more and 50 kV / mm or less. This is because the adhesive layer 10 can reduce its adhesive strength more stably after application of an electric pulse.

[0015] The dielectric strength of the first adhesive layer 10a may be any value that allows the adhesive layer 10 to stably reduce its adhesive strength after application of an electric pulse. The dielectric strength of the first adhesive layer 10a is preferably 0.1 kV / mm to 60 kV / mm, more preferably 0.5 kV / mm to 50 kV / mm, even more preferably 1 kV / mm to 40 kV / mm, particularly preferably 5 kV / mm to 30 kV / mm, and most preferably 10 kV / mm to 20 kV / mm. This range facilitates adjustment of the difference in dielectric strength between the first adhesive layer 10a and the second adhesive layer 10b, enabling the adhesive strength of the adhesive layer 10 to be more stably reduced after application of an electric pulse. Furthermore, the first adhesive layer 10a can be easily formed using a curable composition containing a conductive material and a resin component.

[0016] The dielectric strength of the second adhesive layer 10b may be any value that allows the adhesive layer 10 to stably reduce its adhesive strength after application of an electric pulse. The dielectric strength of the second adhesive layer 10b is preferably 1 kV / mm or more and 100 kV / mm or less, more preferably 10 kV / mm or more and 90 kV / mm or less, even more preferably 20 kV / mm or more and 80 kV / mm or less, and particularly preferably 40 kV / mm or more and 70 kV / mm or less. This range facilitates adjustment of the difference in dielectric strength between the first adhesive layer 10a and the second adhesive layer 10b, thereby enabling the adhesive strength of the adhesive layer 10 to be more stably reduced after application of an electric pulse. Furthermore, the second adhesive layer 10b can be easily formed using a curable composition containing a resin component or a conductive material and a resin component.

[0017] A-2. Shape and Arrangement Pattern of the First Adhesive Layer and the Second Adhesive Layer In the present disclosure, the shape and arrangement of the first adhesive layer 10a and the second adhesive layer 10b are not particularly limited. For example, as shown in FIGS. 1(a) and 1(b), a rectangular first adhesive layer 10a may be arranged such that the centers of gravity of the adhesive layer 10 and the first adhesive layer 10a coincide in a planar view, and the entire periphery of the first adhesive layer 10a is adjacent to the second adhesive layer 10b in a planar view. Arranging the first adhesive layer 10a and the second adhesive layer 10b in this manner makes it possible to generate an internal discharge at the center of the adhesive layer 10 in a planar view upon application of an electric pulse, thereby more stably reducing the adhesive strength of the adhesive layer 10 after application of the electric pulse. In this case, it is preferable that the thicknesses of the first adhesive layer 10a and the second adhesive layer 10b are the same. This is because the adhesive layer 10 has a uniform thickness, resulting in excellent adhesive strength when a first member and a second member are joined via the adhesive layer 10.

[0018] 2(a) and 2(b), the second adhesive layer 10b may be formed so as to cover not only the entire periphery of the first adhesive layer 10a in plan view but also the upper surface. That is, there may be a portion where the first adhesive layer 10a and the second adhesive layer 10b are laminated in this order. Even when the first adhesive layer 10a and the second adhesive layer 10b are arranged in this manner, an internal discharge can be generated in the center of the adhesive layer 10 in plan view, i.e., the laminated portion, which has a lower dielectric strength than the portion where only the second adhesive layer 10b is formed, upon application of an electric pulse, thereby more stably reducing the adhesive strength of the adhesive layer 10 after application of an electric pulse. In this case, too, it is preferable that the thickness of the adhesive layer 10 is uniform.

[0019] The arrangement pattern of the first adhesive layer 10a and the second adhesive layer 10b may be a pattern in which a portion of the periphery of the first adhesive layer 10a is adjacent to the second adhesive layer 10b, as exemplified in Figures 3(a) and 3(b), but is preferably an arrangement pattern in which the entire periphery of the first adhesive layer 10a is adjacent to the second adhesive layer 10b, as already described in Figures 1 and 2. By forming the first adhesive layer 10a and the second adhesive layer 10b in such an arrangement pattern, it is possible to more reliably generate an internal discharge within the adhesive layer 10 when an electric pulse is applied, and it is possible to more stably reduce the adhesive strength of the adhesive layer 10 after the electric pulse is applied.

[0020] The planar shape of the first adhesive layer 10a is not particularly limited, and may be a polygonal shape as shown in Figures 1(a) and 2(a) already described, or a circular shape as exemplified in Figure 4(a). The number of first adhesive layers 10a in the adhesive layer 10 may be one as shown in Figures 1 and 2 already described, or two or more as exemplified in Figure 4(b).

[0021] The area of ​​the first adhesive layer 10a may be any area that can provide an adhesive layer 10 that can stably reduce the adhesive strength after application of an electric pulse. 2 It is preferable that the thickness is 3 mm or more. 2 More than 200 mm 2More preferably, it is 5 mm or less. 2 More than 100 mm 2 Even more preferably, it is 10 mm or less. 2 Over 80mm 2 Even more preferably, it is 15 mm or less. 2 60mm or more 2 It is particularly preferable that the length is 20 mm or less. 2 Over 40mm 2 It is most preferable that the area be less than or equal to 100 mm. This is because it becomes easier to stably generate discharge in the adhesive layer 10, particularly in the first adhesive layer 10a, due to the application of an electric pulse, resulting in an adhesive layer 10 that can more stably reduce its adhesive strength after the application of an electric pulse. Note that the area of ​​the first adhesive layer 10a refers to the area observed when the adhesive layer 10 is viewed in plan. Furthermore, when the adhesive layer 10 has two or more first adhesive layers 10a, the area refers to the area of ​​each of the first adhesive layers 10a.

[0022] The distance between the end of the first adhesive layer 10a and the end of the adhesive layer 10 (hereinafter, sometimes referred to as the end-to-end distance). That is, the width of the second adhesive layer 10b separating the first adhesive layer 10a and the end of the adhesive layer 10 may be any width that allows the adhesive layer 10 to stably reduce its adhesive strength after application of an electric pulse. The width is preferably 1 mm or more, more preferably 5 mm or more, and even more preferably 8 mm or more. This is because it makes it easier to stably generate discharge in the adhesive layer 10, particularly in the first adhesive layer 10a, due to the application of an electric pulse, resulting in an adhesive layer 10 that can more stably reduce its adhesive strength after application of an electric pulse. Note that the end-to-end distance refers to the shortest distance L1 between the end of the first adhesive layer 10a and the end of the adhesive layer 10 in a plan view, as shown in Figures 4(a) and 4(b) already described.

[0023] The thickness of the first adhesive layer 10a may be any thickness that allows the adhesive layer 10 to stably reduce its adhesive strength after application of an electric pulse. The thickness of the first adhesive layer 10a is preferably 30 to 200 mm, more preferably 50 to 150 mm, even more preferably 80 to 120 mm, even more preferably 90 to 110 mm, and particularly preferably 95 to 105 mm. It is most preferable that the thickness of the first adhesive layer 10a and the second adhesive layer 10b be the same, relative to the thickness 100 of the second adhesive layer 10b. This is because it facilitates the formation of a laminate with excellent adhesive strength before application of an electric pulse. Furthermore, the adhesive layer 10 allows the adhesive strength of the adhesive layer 10 to be stably reduced after application of an electric pulse, even without forming conductive protrusions or the like on the first or second member constituting the laminate for dielectric breakdown of the adhesive layer 10. Therefore, it is possible to obtain adhesive layer 10 with a uniform thickness, and since the first member and second member can be obtained as recycled products without protrusions, etc., it becomes easy to use the recycled products. Note that the thicknesses of first adhesive layer 10a and second adhesive layer 10b are the thicknesses at the thinnest locations of each part when adhesive layer 10 is viewed in cross section.

[0024] The thickness of the first adhesive layer 10a is preferably 1 μm or more and 2 mm or less, more preferably 10 μm or more and 1 mm or less, even more preferably 50 μm or more and 500 μm or less, and particularly preferably 100 μm or more and 300 μm or less, because this results in an adhesive layer 10 that can more stably reduce the adhesive strength after application of an electric pulse.

[0025] The thickness of the second adhesive layer 10b may be any thickness that allows the adhesive layer 10 to stably reduce its adhesive strength after application of an electric pulse. The thickness of the second adhesive layer 10b is preferably 1 μm to 2 mm, more preferably 10 μm to 1 mm, even more preferably 50 μm to 500 μm, and particularly preferably 100 μm to 300 μm. This is because the adhesive layer 10 can have a more stable reduction in adhesive strength after application of an electric pulse.

[0026] A-3. Adhesive Layer Forming Materials The first adhesive layer 10a and the second adhesive layer 10b may be any material capable of forming an adhesive layer 10 capable of stably reducing adhesive strength after application of an electric pulse. However, materials containing a cured resin component are preferred. It is more preferred that the first adhesive layer 10a contains a cured resin component and a conductive material, and the second adhesive layer 10b contains a cured resin component. This is because applying a curable composition containing a resin component in a pattern to the respective formation locations of the first adhesive layer 10a and the second adhesive layer 10b and curing the composition facilitates forming the first adhesive layer 10a and the second adhesive layer 10b in the desired positions and shapes. This is also because it facilitates forming an adhesive layer 10 with excellent adhesive strength before application of an electric pulse.

[0027] The material for forming the first adhesive layer 10a may be any material that can form the first adhesive layer 10a with the desired dielectric strength, but it is preferable that the first adhesive layer 10a contain a cured product of a conductive material and a resin component, because the first adhesive layer 10a can be easily formed using a curable composition containing the conductive material and the resin component.

[0028] Examples of the resin component include epoxy resins, acrylic resins, and urethane resins. This is because the first adhesive layer 10a can be easily formed. Furthermore, it is easy to form an adhesive layer with excellent adhesive strength before the application of an electric pulse. In the present disclosure, the resin component may be any component that can form an adhesive layer 10 that can stably reduce adhesive strength after the application of an electric pulse. However, it is preferable for the resin component to contain an epoxy resin, a urethane resin, or the like, more preferably an epoxy resin, and even more preferably both an epoxy resin and a urethane resin. This is because the adhesive layer can be easily formed and it is easy to form an adhesive layer 10 with excellent adhesive strength before the application of an electric pulse.

[0029] The content of the resin component may be any content that allows the adhesive layer 10 to stably reduce its adhesive strength after application of an electric pulse. Preferably, the content is 50 parts by mass or more, more preferably 70 parts by mass or more and 99 parts by mass or less, even more preferably 5 parts by mass or more and 95 parts by mass or less, and particularly preferably 80 parts by mass or more and 90 parts by mass or less, per 100 parts by mass of the first adhesive layer 10a. This is because the adhesive layer 10 is easily formed and can easily be an adhesive layer 10 that has excellent adhesive strength before application of an electric pulse. When a plurality of resin components are contained, the content of the resin components can be the total of the resin components contained in the first adhesive layer 10a. When the resin component is contained in the first adhesive layer 10a as a cured product of the resin component, the content of the resin component can be the total of the components derived from the resin component in the cured product.

[0030] When the resin component contains an epoxy-based resin, the content of the epoxy-based resin may be any content that enables the formation of an adhesive layer 10 that can stably reduce its adhesive strength after application of an electric pulse. The content of the epoxy-based resin is preferably 40 parts by mass or more, more preferably 50 parts by mass or more and 90 parts by mass or less, even more preferably 60 parts by mass or more and 80 parts by mass or less, and particularly preferably 65 parts by mass or more and 75 parts by mass or less, per 100 parts by mass of the first adhesive layer 10a. This is because the first adhesive layer 10a can be easily formed and an adhesive layer 10 that has excellent adhesive strength in the state before application of an electric pulse can be easily formed.

[0031] When the resin component contains a urethane-based resin, the content of the urethane-based resin may be any content that enables the adhesive layer 10 to stably reduce its adhesive strength. The content of the urethane-based resin is preferably 1 part by mass or more, more preferably 5 parts by mass or more and 50 parts by mass or less, even more preferably 10 parts by mass or more and 30 parts by mass or less, and particularly preferably 15 parts by mass or more and 25 parts by mass or less, per 100 parts by mass of the first adhesive layer 10a. This is because the adhesive layer 10 is easily formed and can easily be made to have excellent adhesive strength before the application of an electric pulse.

[0032] A method for forming the first adhesive layer 10a includes, for example, a method including a step of applying a first curable composition containing a conductive material and a resin component to the formation area of ​​the first adhesive layer 10a, and a step of curing the first curable composition.

[0033] The conductive material may be any material that can provide a desired decrease in adhesive strength in the adhesive layer 10 after application of an electric pulse, and examples thereof include a conductive carbon material, a metal material, and a metal-coated resin material. In the present disclosure, the conductive material is preferably a conductive carbon material or a metal material, and more preferably a conductive carbon material, because this results in an adhesive layer 10 that can more stably decrease in adhesive strength after application of an electric pulse.

[0034] The content of the conductive material, expressed in vol%, may be such that the desired reduction in adhesive strength is obtained in the adhesive layer 10 after application of an electric pulse, but it is preferable that the content in the first adhesive layer 10a be 0.03 vol% or more and 40 vol% or less, more preferably 0.1 vol% or more and 25 vol% or less, even more preferably 0.5 vol% or more and 15 vol% or less, particularly preferably 1 vol% or more and 10 vol% or less, and most preferably 2.5 vol% or more and 5 vol% or less. The content of the conductive material, expressed in parts by mass, may be such that the desired reduction in adhesive strength of the adhesive layer 10 is obtained after application of the electric pulse. Preferably, the content is 0.05 to 40 parts by mass, preferably 0.1 to 35 parts by mass, more preferably 0.2 to 30 parts by mass, even more preferably 0.5 to 20 parts by mass, even more preferably 1 to 20 parts by mass, particularly preferably 1.5 to 10 parts by mass, and most preferably 3 to 8 parts by mass. This range facilitates adjustment of the difference in dielectric strength between the first adhesive layer 10a and the second adhesive layer 10b, enabling a more stable reduction in the adhesive strength of the adhesive layer 10 after application of the electric pulse. Furthermore, the adhesive layer 10 exhibits excellent adhesive strength before application of the electric pulse.

[0035] The material for forming the second adhesive layer 10b may be any material capable of forming the second adhesive layer 10b with the desired dielectric strength, but it is preferred that the second adhesive layer 10b does not contain a conductive material or contains a smaller amount of conductive material than the first adhesive layer 10a and a cured product of a resin component, since the second adhesive layer 10b can be easily formed using a curable composition containing a resin component or a conductive material and a resin component.

[0036] The resin component may be the same as that of the first adhesive layer 10a. The content of the resin component is preferably 70 parts by mass or more, more preferably 75 parts by mass or more and 99 parts by mass or less, even more preferably 80 parts by mass or more and 95 parts by mass or less, and particularly preferably 85 parts by mass or more and 92 parts by mass or less, per 100 parts by mass of the second adhesive layer 10b. When the second curable composition contains multiple resin components, the content of the resin components may be the total of the resin components contained in the second adhesive layer 10b.

[0037] When the resin component contains an epoxy resin described below, the content of the epoxy resin may be any content that allows the adhesive layer 10 to stably reduce its adhesive strength after application of an electric pulse. The content of the epoxy resin is preferably 40 parts by mass or more, more preferably 50 parts by mass or more and 90 parts by mass or less, even more preferably 60 parts by mass or more and 80 parts by mass or less, and particularly preferably 65 parts by mass or more and 75 parts by mass or less, per 100 parts by mass of the second adhesive layer 10b. This is because the adhesive layer 10 is easily formed and can easily be made into an adhesive layer 10 that has excellent adhesive strength before application of an electric pulse.

[0038] When the resin component contains a urethane-based resin, as described below, the content of the urethane-based resin may be any content that allows the adhesive layer 10 to stably reduce its adhesive strength after application of an electric pulse. The content of the urethane-based resin is preferably 1 part by mass or more, more preferably 5 parts by mass or more and 50 parts by mass or less, even more preferably 10 parts by mass or more and 30 parts by mass or less, and particularly preferably 15 parts by mass or more and 25 parts by mass or less, per 100 parts by mass of the second adhesive layer 10b. This is because the adhesive layer 10 is easily formed and can easily be made to have excellent adhesive strength before application of an electric pulse.

[0039] The conductive material may be the same as that contained in the first adhesive layer 10a. When the conductive material is the same as that contained in the first adhesive layer 10a, the content of the conductive material may be less than that of the first adhesive layer 10a. The content of the conductive material is preferably 20 parts by weight or less, more preferably 10 parts by weight or less, even more preferably 5 parts by weight or less, even more preferably 2 parts by weight or less, particularly preferably 1 part by weight or less, and most preferably 0 parts by weight, i.e., no conductive material is contained. This makes it easier to increase the difference in dielectric strength between the first adhesive layer 10a and the second adhesive layer 10b, and more stably achieves the desired reduction in adhesive strength of the adhesive layer 10 after application of an electric pulse.

[0040] The method for forming the second adhesive layer 10b may be any method that can form a second adhesive layer 10b with the desired dielectric strength, but if the second adhesive layer 10b contains a cured product of a resin component, for example, a method including a step of applying a second curable composition containing a resin component to the formation area of ​​the second adhesive layer 10b and a step of curing the second curable composition can be used.

[0041] In the formation method, the step of curing the second curable composition may be carried out simultaneously with the step of curing the first curable composition. That is, the formation method of the adhesive layer 10 may include the steps of: applying a first curable composition containing a conductive material and a resin component to a formation region of the first adhesive layer 10a; applying a second curable composition containing a conductive material that does not contain a conductive material or a conductive material in an amount less than that of the first curable composition and a resin component to a formation region of the second adhesive layer 10b; and curing the first curable composition and the second curable composition.

[0042] The first curable composition and the second curable composition for forming the first adhesive layer 10a and the second adhesive layer 10b will be described in detail in the section "B. Curable composition" below.

[0043] The application area of ​​the first curable composition and the second curable composition may be on the first member or the second member to be adhered by the adhesive layer 10, or may be on a substrate different from the first member and the second member to be adhered. In the present disclosure, the application area is preferably on the first member or the second member. This is because the adhesive layer 10 can be easily formed. The application method of the first curable composition and the second curable composition may be any method that can form the first adhesive layer 10a and the second adhesive layer 10b in a desired pattern, and examples thereof include bar coating, knife coating, roll coating, blade coating, die coating, gravure coating, curtain coating, and inkjet coating.

[0044] More specifically, the method for applying the first curable composition and the second curable composition may be a method of applying them only to the formation regions of the first adhesive layer 10a and the second adhesive layer 10b using an inkjet method or the like, or a method of placing a frame having an opening in the formation region of the first adhesive layer 10a, applying the first curable composition, removing the frame, and then applying the second curable composition to the formation region of the second adhesive layer 10b. Furthermore, when the second adhesive layer 10b is formed so as to also cover the upper surface of the first adhesive layer 10a, as shown in Figures 2(a) and 2(b) above, a method of placing a frame having an opening in the formation region of the first adhesive layer 10a, applying the first curable composition, removing the frame, and then applying the second curable composition so as to cover both the formation region of the first adhesive layer 10a and the formation region of the second adhesive layer 10b may be used.

[0045] The curing method may be any method capable of curing the first curable composition and the second curable composition, and may vary depending on the types of resin components, curing agent components, etc. When the resin components are epoxy resins, urethane resins, etc., the curing method is preferably a heating method. The heating temperature is preferably 50°C or higher and 250°C or lower, more preferably 100°C or higher and 220°C or lower, and even more preferably 150°C or higher and 200°C or lower.

[0046] A-4. Uses of the Adhesive Layer The adhesive layer 10 can be used in applications where it is desirable to remove members bonded by the adhesive layer 10 and reuse them as recycled products. Examples of such applications include bonding home appliances, communication device terminals, toys, daily necessities, industrial equipment, and automobile interior parts.

[0047] B. Curable Composition Next, the curable composition that forms the adhesive layer 10 will be described. The curable composition of the present disclosure is used to form the adhesive layer 10, and includes a curable composition for forming the first adhesive layer 10a (hereinafter, sometimes referred to as the first curable composition) and a curable composition for forming the second adhesive layer 10b (hereinafter, sometimes referred to as the second curable composition). Hereinafter, the curable composition of the present disclosure will be described separately as the first curable composition and the second curable composition.

[0048] B-1. First Curable Composition The first curable composition of the present disclosure is a curable composition for forming the first adhesive layer 10a. Such a first curable composition is not particularly limited as long as it can form the first adhesive layer 10a, but preferably contains a resin component and a conductive material. That is, the first curable composition of the present disclosure is a curable composition containing a conductive material and a resin component, and preferably contains the first adhesive layer 10a and a second adhesive layer 10b having a higher dielectric strength than the first adhesive layer 10a, and is used to form the first adhesive layer 10a of the adhesive layer 10 used in electric pulse peeling. This is because the first adhesive layer 10a can be easily formed.

[0049] The resin component used in the first curable composition refers to a resin that can be polymerized by reacting directly with itself or by reacting with itself via a curing agent component such as a curing agent, curing catalyst, or polymerization initiator. Examples of such resin components include epoxy-based resins, acrylic-based resins, and urethane-based resins. This is because the adhesive layer 10 can be easily formed. Furthermore, it is easy to obtain an adhesive layer 10 with excellent adhesive strength before the application of an electric pulse. In the present disclosure, the resin component may be any resin that can provide an adhesive layer 10 that can stably reduce its adhesive strength after the application of an electric pulse. Preferably, the resin component includes an epoxy-based resin, a urethane-based resin, or the like, more preferably an epoxy-based resin, and even more preferably both an epoxy-based resin and a urethane-based resin. This is because the adhesive layer 10 can be easily formed and it is easy to obtain an adhesive layer 10 with excellent adhesive strength before the application of an electric pulse.

[0050] The epoxy equivalent of the epoxy resin may be any one that can provide an adhesive layer 10 that can stably reduce its adhesive strength after application of an electric pulse. The epoxy equivalent is preferably 50 g / eq or more and 5,000 g / eq or less, more preferably 100 g / eq or more and 3,000 g / eq or less, and even more preferably 150 g / eq or more and 1,500 g / eq or less. This is because the adhesive layer 10 is easily formed and can easily be an adhesive layer 10 that has excellent adhesive strength in the state before application of an electric pulse.

[0051] Examples of the epoxy resin include an epoxy compound having an epoxy group and a modified epoxy compound obtained by modifying an epoxy compound. The epoxy resin may be any resin capable of forming an adhesive layer 10 capable of stably reducing the adhesive strength after application of an electric pulse, but it preferably contains an epoxy compound, and more preferably contains an epoxy compound and a modified epoxy compound. This is because the adhesive layer 10 can be easily formed and can easily be formed into an adhesive layer 10 having excellent adhesive strength before application of an electric pulse.

[0052] Examples of such epoxy compounds include monoglycidyl ether compounds, monoglycidyl ester compounds, polyglycidyl ether compounds of mononuclear polyhydric phenol compounds, polyglycidyl ether compounds of polynuclear polyhydric phenol compounds or alkylene oxide adducts of the polynuclear polyhydric phenol compounds, polyglycidyl ethers of polyhydric alcohols, homopolymers or copolymers of glycidyl esters of aliphatic, aromatic or alicyclic polybasic acids and glycidyl methacrylate, epoxidized products of cyclic olefin compounds, epoxidized conjugated diene polymers, and heterocyclic compounds.

[0053] Examples of the polynuclear polyhydric phenol compound include a compound having a naphthalene structure, a compound having a biphenol structure, a compound having a bisphenol structure, and a novolac phenol resin. Examples of the compound having a naphthalene structure include dihydroxynaphthalene. Examples of the compound having a biphenol structure include biphenol.

[0054] Examples of compounds having a bisphenol structure include compounds in which two hydroxyphenyl groups are bonded by one atom, such as methylenebisphenol (bisphenol F), methylenebis(ortho-cresol); ethylidenebisphenol; compounds having a bisphenol A structure such as isopropylidenebisphenol (bisphenol A), isopropylidenebis(ortho-cresol), and tetrabromobisphenol A; and 1,1,3-tris(4-hydroxyphenyl)butane, 1,1,2,2-tetra(4-hydroxyphenyl)ethane, thiobisphenol, sulfobisphenol, and oxybisphenol. The phrase "two hydroxyphenyl groups bonded by one atom" refers to a linking chain length of one atom connecting the benzene rings of the two hydroxyphenyl groups. The bisphenol A structure refers to a structure in which two hydroxyphenyl groups are bonded to each other via an isopropylidene group on the benzene rings, and polyglycidyl ethers of polyhydric phenol compounds having this structure include so-called bisphenol A epoxy resins. Furthermore, examples of compounds having a bisphenol structure in which two hydroxyphenyl groups are bonded by two or more atoms include 1,3-bis(4-hydroxycumylbenzene) and 1,4-bis(4-hydroxycumylbenzene).

[0055] Examples of the novolac type phenolic resin include phenol novolac, orthocresol novolac, ethylphenol novolac, butylphenol novolac, octylphenol novolac, resorcinol novolac, and terpene phenol. Examples of the alkylene oxide constituting the alkylene oxide adduct of the polynuclear polyhydric phenol compound include ethylene oxide and propylene oxide.

[0056] Examples of the monoglycidyl ether compounds include monoglycidyl ether compounds such as phenyl glycidyl ether, allyl glycidyl ether, methyl glycidyl ether, butyl glycidyl ether, sec-butyl glycidyl ether, 2-ethylhexyl glycidyl ether, 2-methyloctyl glycidyl ether, and stearyl glycidyl ether; versatic acid glycidyl ester; etc. Examples of the mononuclear polyhydric phenol compounds include hydroquinone, resorcinol, pyrocatechol, and phloroglucinol.

[0057] Examples of the polyhydric alcohols include ethylene glycol, propylene glycol, butylene glycol, hexanediol, polyglycol, thiodiglycol, glycerin, trimethylolpropane, pentaerythritol, sorbitol, etc. Examples of the aliphatic, aromatic, or alicyclic polybasic acids constituting the glycidyl esters of aliphatic, aromatic, or alicyclic polybasic acids and the homopolymers or copolymers of glycidyl methacrylate include maleic acid, fumaric acid, itaconic acid, succinic acid, glutaric acid, suberic acid, adipic acid, azelaic acid, sebacic acid, dimer acid, trimer acid, phthalic acid, isophthalic acid, terephthalic acid, trimellitic acid, trimesic acid, pyromellitic acid, tetrahydrophthalic acid, hexahydrophthalic acid, and endomethylenetetrahydrophthalic acid.

[0058] Examples of the epoxidized cyclic olefin compounds include vinylcyclohexene diepoxide, dicyclopentadiene diepoxide, 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate, 3,4-epoxy-6-methylcyclohexylmethyl-6-methylcyclohexanecarboxylate, bis(3,4-epoxy-6-methylcyclohexylmethyl)adipate, etc. Examples of the epoxidized conjugated diene polymers include epoxidized polybutadiene and epoxidized styrene-butadiene copolymers, etc. Examples of the heterocyclic compounds include triglycidyl isocyanurate, etc.

[0059] In the present disclosure, the epoxy compound preferably includes a polyglycidyl ether compound of a polynuclear polyhydric phenol compound or its alkylene oxide adduct, or a polyglycidyl ether of a polyhydric alcohol, more preferably a polyglycidyl ether compound of a polynuclear polyhydric phenol compound or its alkylene oxide adduct, even more preferably a polyglycidyl ether compound of a polynuclear polyhydric phenol compound, even more preferably a bisphenol-type epoxy compound that is a polyglycidyl ether compound of a bisphenol compound, and particularly preferably a bisphenol A-type epoxy compound that is a polyglycidyl ether compound of bisphenol A. This is because the adhesive layer 10 can be easily formed. Also, this is because the adhesive layer 10 can easily be formed to have excellent adhesive strength before the application of an electric pulse.

[0060] The modified epoxy compound may be any compound modified from the epoxy compounds described above, such as urethane-modified urethane-modified epoxy resins, chelate-modified epoxy resins modified with phosphoric acid, and rubber-modified epoxy resins modified to include a rubber component. In the present disclosure, the modified epoxy compound may be any compound capable of forming an adhesive layer 10 capable of stably reducing the adhesive strength after application of an electric pulse, but preferably includes a chelate-modified epoxy resin or a rubber-modified epoxy resin. This is because the adhesive layer 10 can be easily formed. Furthermore, this is because it is easy to form an adhesive layer 10 that has excellent adhesive strength before application of an electric pulse.

[0061] The chelate-modified epoxy resin is one modified with phosphoric acid, and specific examples thereof include a resin obtained by reacting an epoxy compound with phosphoric acid, and a chelate-urethane-modified epoxy resin obtained by reacting an epoxy compound, phosphoric acid, and polyurethane having an isocyanate group.

[0062] The rubber-modified epoxy resin includes a rubber component obtained by homopolymerizing isoprene rubber, butadiene, styrene, acrylonitrile, chloroprene, or the like, or by copolymerizing two or more of the components, and contains an epoxy group at the terminal.

[0063] The urethane-modified epoxy resin is obtained by reacting an epoxy compound having at least one hydroxyl group in the molecule with a polyurethane having a residual isocyanate group, and the polyurethane is obtained by reacting a polyhydroxy compound with a polyisocyanate compound. During the reaction, the polyisocyanate compound can be used in an excess amount relative to the polyhydroxy compound.

[0064] The method for producing the epoxy compound containing at least one hydroxyl group is not particularly limited, but examples thereof include a method in which 1 to 10 equivalents of epichlorohydrin and an alkali metal hydroxide such as sodium hydroxide are reacted with each other relative to 1 equivalent of the hydroxyl groups of a polyol having at least two hydroxyl groups at 40 to 150°C for 1 to 20 hours.

[0065] The polyol containing at least two hydroxyl groups is not particularly limited, but examples thereof include polyphenols, aliphatic polyols, and alicyclic polyols.

[0066] Examples of the polyphenols include bisphenol A, bisphenol F, tetrabromobisphenol A, phenol novolak, brominated phenol novolak, cresol novolak, brominated cresol novolak, 4,4'-dihydroxybiphenyl, and 1,1,2,2-tetrakis(hydroxyphenyl)ethane.

[0067] Examples of the aliphatic polyols include polyhydric alcohols such as ethylene glycol and propylene glycol, linear or branched low-molecular-weight polyols such as butanediol, pentanediol, hexanediol, octanediol, decanediol, glycerin, trimethylolpropane, trimethylolethane, pentaerythritol, dipentaerythritol, and neopentyl glycol, and ethylene oxide or propylene oxide adducts thereof.

[0068] Examples of the alicyclic polyol include cyclohexanediol, cyclohexanetriol, cyclohexanedimethanol, isopropylidenedicyclohexanol, decalindiol, and tricyclodecane dimethanol.

[0069] Among the polyols having at least two hydroxyl groups described above, it is preferable to use polyphenols, which are highly reactive and easy to produce, and it is more preferable to use bisphenol A and / or bisphenol F, which are inexpensively available.

[0070] Examples of polyhydroxy compounds used to produce the polyurethane include polyether polyols, polyester polyols, polycarbonate polyols, polyesteramide polyols, acrylic polyols, and polyurethane polyols.

[0071] As the polyether polyol, an alkylene oxide adduct of a polyol is preferably used, and the alkylene oxide preferably has 2 to 4 carbon atoms.

[0072] Examples of polyols used to produce the polyether polyols include aliphatic dihydric alcohols such as ethylene glycol, propylene glycol, 1,4-butylene glycol (tetramethylene glycol), and neopentane glycol; glycerin, trioxyisobutane, 1,2,3-butanetriol, 1,2,3-pentanetriol, 2-methyl-1,2,3-propanetriol, 2-methyl-2,3,4-butanetriol, 2-ethyl-1,2,3-butanetriol, 2,3,4-pentanetriol, 2,3,4-hexanetriol, and 4-propyl-3,4,5- Examples of suitable polyhydric alcohols include trihydric alcohols such as heptanetriol, 2,4-dimethyl-2,3,4-pentanetriol, pentamethylglycerin, pentaglycerin, 1,2,4-butanetriol, 1,2,4-pentanetriol, and trimethylolpropane; tetrahydric alcohols such as erythritol, pentaerythritol, 1,2,3,4-pentanetetrol, 2,3,4,5-hexanetetrol, 1,2,3,5-pentanetetrol, and 1,3,4,5-hexanetetrol; pentahydric alcohols such as adonite, arabidopsis, and xylitol; and hexahydric alcohols such as sorbitol, mannitol, and idit. Among these, preferred polyhydric alcohols are dihydric to tetrahydric alcohols, with propylene glycol, 1,4-butylene glycol, and glycerin being particularly preferred.

[0073] Examples of the alkylene oxide constituting the polyether polyol include ethylene oxide, propylene oxide, and butylene oxide (tetramethylene oxide), with propylene oxide and butylene oxide being particularly preferred.

[0074] Examples of the polyester polyol include conventionally known polyesters produced from polycarboxylic acids and polyhydric alcohols, and polyesters obtained from lactones.

[0075] Examples of polycarboxylic acids used to produce polyester polyols include benzenetricarboxylic acid, adipic acid, succinic acid, suberic acid, sebacic acid, oxalic acid, methyl adipic acid, glutaric acid, pimelic acid, azelaic acid, phthalic acid, terephthalic acid, isophthalic acid, thiodipropionic acid, maleic acid, fumaric acid, citraconic acid, and itaconic acid.

[0076] Examples of polyols used to produce polyester polyols include ethylene glycol, propylene glycol, 1,4-butanediol, 1,3-butanediol, 1,5-pentanediol, 1,6-hexanediol, bis(hydroxymethylchlorohexane), diethylene glycol, 2,2-dimethylpropylene glycol, 1,3,6-hexanetriol, trimethylolpropane, pentaerythritol, sorbitol, glycerin, etc. In addition to these polyols, polyhydroxy compounds such as polytetramethylene glycol and polycaprolactone glycol can also be used in partial substitution.

[0077] Examples of the polycarbonate polyol include those obtained by a dealcoholization reaction between a diol and diphenyl carbonate, a dealcoholization reaction between a diol and a dialkyl carbonate, a deglycolization reaction between a diol and an alkylene carbonate, etc. Examples of the diol include ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, neopentyl glycol, 3-methyl-1,5-pentanediol, 3,3-dimethylolheptane, etc.

[0078] Examples of polyisocyanate compounds used to produce the polyurethane include propane-1,2-diisocyanate, 2,3-dimethylbutane-2,3-diisocyanate, 2-methylpentane-2,4-diisocyanate, octane-3,6-diisocyanate, 3,3-dinitropentane-1,5-diisocyanate, octane-1,6-diisocyanate, 1,6-hexamethylene diisocyanate (HDI), trimethylhexamethylene diisocyanate, lysine diisocyanate, triisocyanate, methyl ... Examples of the polyisocyanate include diisocyanate (TDI), xylylene diisocyanate, meta-tetramethylxylylene diisocyanate, isophorone diisocyanate (3-isocyanatomethyl-3,5,5-trimethylcyclohexylisocyanate), 1,3- or 1,4-bis(isocyanatomethyl)cyclohexane, diphenylmethane-4,4'-diisocyanate (MDI), dicyclohexylmethane-4,4'-diisocyanate (hydrogenated MDI), hydrogenated tolylene diisocyanate, and mixtures thereof. These polyisocyanate compounds may be isocyanurates obtained by trimerization.

[0079] Examples of the urethane resin include polyurethane and block urethane resin.

[0080] As described above, polyurethane is obtained by reacting a polyhydroxy compound with a polyisocyanate compound. The polyhydroxy compound and isocyanate compound used in producing polyurethane may be the same as those described above for the urethane-modified epoxy resin.

[0081] The production of polyurethane by reacting a polyhydroxy compound with a polyisocyanate compound can be carried out by a conventional method.

[0082] As the blocked urethane resin, a blocked urethane resin obtained by blocking, with a blocking agent, polyurethane having an isocyanate (NCO) content of 0.1 to 10 mass % obtained by reacting a polyhydroxy compound with an excess amount of a polyisocyanate compound is preferably used.

[0083] Examples of blocking agents include active methylene compounds such as malonic acid diesters (diethyl malonate, etc.), acetylacetone, and acetoacetic acid esters (ethyl acetoacetate, etc.); oxime compounds such as acetoxime, methyl ethyl ketoxime (MEK oxime), and methyl isobutyl ketoxime (MIBK oxime); monohydric alcohols such as methyl alcohol, ethyl alcohol, propyl alcohol, butyl alcohol, heptyl alcohol, hexyl alcohol, octyl alcohol, 2-ethylhexyl alcohol, isononyl alcohol, and stearyl alcohol, or isomers thereof; ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, and the like; glycol derivatives such as ethylene glycol monobutyl ether, ethyl diglycol, ethyl triglycol, ethylene glycol monobutyl ether, and butyl diglycol; amine compounds such as dicyclohexylamine; phenols such as phenol, cresol, ethylphenol, n-propylphenol, isopropylphenol, butylphenol, tert-butylphenol, octylphenol, nonylphenol, dodecylphenol, cyclohexylphenol, chlorophenol, bromophenol, resorcinol, catechol, hydroquinone, bisphenol A, bisphenol S, bisphenol F, and naphthol; ε-caprolactone, ε-caprolactam, and the like.

[0084] The blocking reaction for obtaining a blocked polyurethane from a polyurethane and a blocking agent can be carried out by a known reaction method.

[0085] As the blocked urethane resin, in addition to the blocked urethane resin obtained by reacting polyurethane with a blocking agent, a blocked isocyanate resin obtained by modifying a polyisocyanate compound (particularly an isocyanuric compound) with a blocking agent can also be used.

[0086] The block NCO equivalent of the block urethane resin may be any one that can provide an adhesive layer 10 that can stably reduce adhesive strength after application of an electric pulse. The block NCO equivalent is preferably 300 g / eq or more and 5,000 g / eq or less, more preferably 500 g / eq or more and 3,000 g / eq or less, and even more preferably 1,000 g / eq or more and 2,000 g / eq or less. This is because the adhesive layer 10 is easily formed and can easily be an adhesive layer 10 that has excellent adhesive strength in the state before application of an electric pulse.

[0087] As the acrylic resin, known materials can be used, and for example, the same materials as those described in WO 2023 / 136299 can be used.

[0088] The content of the epoxy resin may be any content that can provide an adhesive layer 10 that can stably reduce the adhesive strength after application of an electric pulse. The content of the epoxy resin is preferably 40 parts by mass or more, more preferably 50 parts by mass or more and 90 parts by mass or less, even more preferably 60 parts by mass or more and 80 parts by mass or less, and particularly preferably 65 parts by mass or more and 75 parts by mass or less, per 100 parts by mass of the first curable composition. This is because the adhesive layer 10 is easily formed and can easily be an adhesive layer 10 that has excellent adhesive strength in the state before application of an electric pulse.

[0089] When the epoxy resin contains both an epoxy compound and a modified epoxy compound, the content of the epoxy compound may be any amount that can provide an adhesive layer 10 that can stably reduce the adhesive strength after application of an electric pulse. The content of the epoxy compound is preferably 20 parts by mass or more and 90 parts by mass or less, more preferably 40 parts by mass or more and 90 parts by mass or less, even more preferably 50 parts by mass or more and 80 parts by mass or less, and particularly preferably 55 parts by mass or more and 70 parts by mass or less, per 100 parts by mass of the epoxy resin. This is because the adhesive layer 10 can be easily formed and can easily be an adhesive layer 10 that has excellent adhesive strength in the state before application of an electric pulse.

[0090] The content of the urethane resin may be any content that can provide an adhesive layer 10 that can stably reduce the adhesive strength after application of an electric pulse. The content of the urethane resin is preferably 1 part by mass or more, more preferably 5 parts by mass or more and 50 parts by mass or less, even more preferably 10 parts by mass or more and 30 parts by mass or less, and particularly preferably 15 parts by mass or more and 25 parts by mass or less, per 100 parts by mass of the first curable composition. This is because the adhesive layer 10 is easily formed and can easily be an adhesive layer 10 that has excellent adhesive strength in the state before application of an electric pulse.

[0091] The first curable composition preferably contains a curing agent component such as a curing agent, a curing catalyst, and a polymerization initiator for forming a cured product of the resin component.

[0092] The curing agent may be a latent curing agent or other curing agents. In the present disclosure, the curing agent preferably includes a latent curing agent, because this makes it easier to cure the resin component at the desired timing.

[0093] The latent curing agent can be at least one compound selected from the group consisting of dicyandiamide, modified polyamines, hydrazides, 4,4'-diaminodiphenyl sulfone, boron trifluoride amine complex salts, ureas, and melamine. In the present disclosure, the latent curing agent preferably includes dicyandiamide. This is because the adhesive layer 10 can be easily formed and can easily be an adhesive layer 10 that has excellent adhesive strength in the state before the application of an electric pulse.

[0094] Examples of the modified polyamine include epoxy addition modified amines, amidation modified amines, acrylate modified amines, isocyanate modified amines, and Mannich modified amines.

[0095] Examples of amines for providing the modified polyamine include aliphatic polyamines such as ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, polyoxypropylenediamine, and polyoxypropylenetriamine; alicyclic polyamines such as isophoronediamine, menthenediamine, bis(4-amino-3-methyldicyclohexyl)methane, diaminodicyclohexylmethane, bis(aminomethyl)cyclohexane, N-aminoethylpiperazine, and 3,9-bis(3-aminopropyl)-2,4,8,10-tetraoxaspiro(5.5)undecane; m-phenylenediamine, p-phenylenediamine, and tolylene-2,4-diamine; mononuclear polyamines such as biphenylenediamine, 4,4-diaminodiphenylmethane, 2,5-naphthylenediamine, and 2,6-naphthylenediamine; aromatic polyamines such as biphenylenediamine, 4,4-diaminodiphenylmethane, 2,5-naphthylenediamine, and 2,6-naphthylenediamine; and imidazoles such as 2-methylimidazole, 2-ethyl-4-methylimidazole, 2-isopropylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, and 2-aminopropylimidazole.

[0096] The other curing agents are not particularly limited as long as they are known curing agents, and examples thereof include phenolic resins, aliphatic amines, aromatic amines, acid anhydrides, polythiol compounds, and the like.

[0097] The blending amount of the curing agent is preferably 1 part by mass or more and 100 parts by mass or less, more preferably 2 parts by mass or more and 50 parts by mass or less, even more preferably 3 parts by mass or more and 20 parts by mass or less, and particularly preferably 4 parts by mass or more and 10 parts by mass or less, relative to 100 parts by mass of the resin component, because the adhesive layer 10 can be easily formed and can easily be made to have excellent adhesive strength in the state before the application of the electric pulse.

[0098] Examples of the curing catalyst include phosphines such as triphenylphosphine; phosphonium salts such as tetraphenylphosphonium bromide; imidazoles such as 2-methylimidazole, 2-phenylimidazole, 2-ethyl-4-methylimidazole, 2-undecylimidazole, 1-cyanoethyl-2-methylimidazole, and imidazole silane (for example, 2MUSIZ manufactured by Shikoku Chemical Industry Co., Ltd.); imidazole salts obtained by combining the above imidazoles with trimellitic acid, isocyanuric acid, boron, or the like; benzyldimethylamine, 2 , 4,6-tris(dimethylaminomethyl)phenol and other amines; quaternary ammonium salts such as trimethylammonium chloride; ureas such as 3-(p-chlorophenyl)-1,1-dimethylurea, 3-(3,4-dichlorophenyl)-1,1-dimethylurea, 3-phenyl-1,1-dimethylurea (1,1-dimethyl-3-phenylurea), isophorone diisocyanate-dimethylurea, and tolylene diisocyanate-dimethylurea; and complex compounds of boron trifluoride with amines, ether compounds, and the like. These curing catalysts may be used alone or in combination of two or more. In the present disclosure, the curing catalyst preferably includes a urea.

[0099] The amount of the curing catalyst to be added is preferably 0.1 parts by mass or more and 15 parts by mass or less, more preferably 0.3 parts by mass or more and 5 parts by mass or less, and even more preferably 0.5 parts by mass or more and 3 parts by mass or less, per 100 parts by mass of the resin component, from the viewpoint of the adhesive strength of the adhesive layer 10 before the application of the electric pulse, because this makes it easy to form the adhesive layer 10 and to obtain an adhesive layer 10 that has excellent adhesive strength in the state before the application of the electric pulse.

[0100] The conductive material contained in the first curable composition may be any material that can achieve a desired decrease in adhesive strength in the adhesive layer 10 after application of an electric pulse, and examples thereof include a conductive carbon material, a metal material, and a metal-coated resin material. In the present disclosure, the conductive material is preferably a conductive carbon material or a metal material, and more preferably a conductive carbon material, because this results in an adhesive layer 10 that can more stably decrease in adhesive strength after application of an electric pulse.

[0101] Examples of the conductive carbon material include carbon black, graphene, carbon nanotubes (CNT), etc. Examples of the metal material include copper, silver, nickel, silver-coated copper, gold-coated copper, silver-coated nickel, gold-coated nickel, etc. Examples of the metal-coated resin material include materials in which resin particles such as acrylic resin particles and urethane resin particles are coated with a metal material such as copper, silver, nickel, or gold.

[0102] The particle size of the conductive material may be any size that results in a desired decrease in adhesive strength in the adhesive layer 10 after application of an electric pulse. The particle size of the conductive material is preferably 0.01 μm to 1000 μm, more preferably 0.015 μm to 500 μm, even more preferably 0.02 μm to 250 μm, even more preferably 0.025 μm to 50 μm, particularly preferably 0.03 μm to 1 μm, and most preferably 0.035 μm to 0.1 μm. This range facilitates adjustment of the difference in dielectric strength between the first adhesive layer 10a and the second adhesive layer 10b, enabling a more stable decrease in adhesive strength of the adhesive layer 10 after application of an electric pulse. This also facilitates forming the first adhesive layer 10a at the desired position. The particle size represents the volume-based D50 and can be measured using a laser diffraction particle size distribution analyzer.

[0103] The particle size of the conductive material may be any size that provides a desired reduction in adhesive strength in the adhesive layer 10 after application of an electric pulse. The particle size of the conductive material is preferably 90 or less relative to the thickness 100 of the adhesive layer 10, more preferably 0.001 to 50, even more preferably 0.003 to 5, even more preferably 0.005 to 1, particularly preferably 0.01 to 0.5, and most preferably 0.015 to 0.1. This range facilitates adjustment of the difference in dielectric strength between the first adhesive layer 10a and the second adhesive layer 10b, enabling a more stable reduction in the adhesive strength of the adhesive layer 10 after application of an electric pulse. Furthermore, this facilitates forming the first adhesive layer 10a at a desired position.

[0104] The content of the conductive material, expressed in vol%, may be any content that results in the desired reduction in adhesive strength in the adhesive layer 10 after application of an electric pulse, but it is preferably 0.03 vol% or more and 40 vol% or less in the first curable composition, more preferably 0.1 vol% or more and 25 vol% or less, even more preferably 0.5 vol% or more and 15 vol% or less, particularly preferably 1 vol% or more and 10 vol% or less, and most preferably 2.5 vol% or more and 5 vol% or less. The content of the conductive material, expressed in parts by mass, may be such that the desired reduction in adhesive strength of the adhesive layer 10 is obtained after application of the electric pulse. Preferably, the content is 0.05 to 40 parts by mass, preferably 0.1 to 35 parts by mass, more preferably 0.2 to 30 parts by mass, even more preferably 0.5 to 20 parts by mass, even more preferably 1 to 20 parts by mass, particularly preferably 1.5 to 10 parts by mass, and most preferably 3 to 8 parts by mass. This range facilitates adjustment of the difference in dielectric strength between the first adhesive layer 10a and the second adhesive layer 10b, enabling the adhesive strength of the adhesive layer 10 to be more stably reduced after application of the electric pulse. Furthermore, using the first curable composition, the first adhesive layer 10a can be easily formed at the desired position. Furthermore, the adhesive layer 10 exhibits excellent adhesive strength before application of the electric pulse.

[0105] The first curable composition may contain components other than the resin component, the curing agent component, the conductive material, etc. Examples of such components include moisture adsorbents such as calcium oxide, non-reactive diluents (plasticizers) such as dioctyl phthalate, dibutyl phthalate, benzyl alcohol, and coal tar; fibrous fillers such as glass fiber, pulp fiber, synthetic fiber, and ceramic fiber; reinforcing materials such as glass cloth, aramid cloth, and carbon fiber; pigments; γ-aminopropyltriethoxysilane, N-β-(aminoethyl)-γ-aminopropyltriethoxysilane, N-β-(aminoethyl)-N'-β-(aminoethyl)-γ-aminopropyltriethoxysilane, γ-anilinopropyltriethoxysilane, γ-glycidoxypropyltriethoxysilane, β-(3,4-epoxycyclohexyl)ethyltriethoxysilane, vinyltriethoxysilane, N -β-(N-vinylbenzylaminoethyl)-γ-aminopropyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-chloropropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, and other silane coupling agents; lubricants such as candelilla wax, carnauba wax, Japan wax, Ibota wax, beeswax, lanolin, spermaceti, montan wax, petroleum wax, aliphatic wax, aliphatic esters, aliphatic ethers, aromatic esters, and aromatic ethers; thickeners; thixotropic agents; antioxidants; light stabilizers; ultraviolet absorbers; flame retardants; antifoaming agents; rust inhibitors; colloidal silica, colloidal alumina, and other commonly used additives may be contained, and adhesive resins such as xylene resins and petroleum resins may also be used in combination.

[0106] The method for preparing the first curable composition may be any method that can mix the conductive material and the resin component. Such a mixing method is not particularly limited, and a general method such as a roll mixer can be used.

[0107] B-2. Second Curable Composition The second curable composition of the present disclosure is a curable composition for forming the second adhesive layer 10b. Such a second curable composition is not particularly limited as long as it can form a second adhesive layer 10b having a higher dielectric strength than the first adhesive layer 10a. However, it is preferable that the second curable composition does not contain a conductive material or contains a conductive material in an amount less than that of the first curable composition, and a resin component. That is, the second curable composition of the present disclosure is a curable composition containing a resin component, and preferably includes the first adhesive layer 10a and a second adhesive layer 10b having a higher dielectric strength than the first adhesive layer 10a, and is used to form the second adhesive layer 10b of an adhesive layer 10 used in electric pulse peeling.

[0108] The resin component used in the second curable composition can be the same as that used in the first curable composition. The content of the resin component is preferably 70 parts by mass or more, more preferably 75 parts by mass or more and 99 parts by mass or less, even more preferably 80 parts by mass or more and 95 parts by mass or less, and particularly preferably 85 parts by mass or more and 92 parts by mass or less, per 100 parts by mass of the second curable composition. When the second curable composition contains multiple resin components, the content of the resin components can be the total of the resin components contained in the second cured product.

[0109] When the resin component contains an epoxy-based resin, the content of the epoxy-based resin may be any content that can form an adhesive layer 10 that can stably reduce the adhesive strength after application of an electric pulse. The content of the epoxy-based resin is preferably 40 parts by mass or more, more preferably 50 parts by mass or more and 90 parts by mass or less, even more preferably 60 parts by mass or more and 80 parts by mass or less, and particularly preferably 65 parts by mass or more and 75 parts by mass or less, per 100 parts by mass of the second curable composition. This is because the adhesive layer 10 is easily formed and can easily be formed into an adhesive layer 10 that has excellent adhesive strength in the state before application of an electric pulse.

[0110] When the resin component contains a urethane-based resin, the content of the urethane-based resin may be any content that allows the formation of an adhesive layer 10 that can stably reduce its adhesive strength after application of an electric pulse. The content of the urethane-based resin is preferably 1 part by mass or more, more preferably 5 parts by mass or more and 50 parts by mass or less, even more preferably 10 parts by mass or more and 30 parts by mass or less, and particularly preferably 15 parts by mass or more and 25 parts by mass or less, per 100 parts by mass of the second curable composition. This is because the adhesive layer 10 is easily formed and can easily be formed into an adhesive layer 10 that has excellent adhesive strength in the state before application of an electric pulse.

[0111] The second curable composition may contain a conductive material to the extent that the second adhesive layer 10b has a higher dielectric strength than the first adhesive layer 10a. When the conductive material is the same as the conductive material contained in the first curable composition, the content of the conductive material may be less than the content of the conductive material in the first curable composition. The content of the conductive material is preferably 20 parts by mass or less, more preferably 10 parts by mass or less, even more preferably 5 parts by mass or less, even more preferably 2 parts by mass or less, particularly preferably 1 part by mass or less, and most preferably 0 parts by mass, i.e., no conductive material is contained. This is because it is easy to increase the difference in dielectric strength between the first adhesive layer 10a and the second adhesive layer 10b, and the desired decrease in adhesive strength of the adhesive layer 10 can be more stably obtained after application of an electric pulse.

[0112] The second curable composition may contain, as components other than the resin component and the conductive material, a curing agent component, other components, etc. The contents of each of these components may be the same as those used in the first curable composition.

[0113] B-3. ​​Set of Curable Compositions The first curable composition and the second curable composition, which are the curable compositions of the present disclosure, may be used as a set. Such a set of curable compositions is not particularly limited as long as it is capable of forming the adhesive layer 10. However, it is preferable that the set is a set of curable compositions used for electric pulse peeling, and includes a first curable composition containing a conductive material and a resin component, and a second curable composition that does not contain the conductive material or contains less of the conductive material than the first curable composition and a resin component. The contents of the first curable composition and the second curable composition used in the set of curable compositions can be the same as those described in the above sections "B-1. First Curable Composition" and "B-2. Second Curable Composition," and therefore, description thereof will be omitted here.

[0114] C. Laminate Figure 5 is a schematic cross-sectional view showing an example of a laminate formed using the adhesive layer of the present disclosure. As illustrated in Figure 5, the laminate 20 of the present disclosure is characterized in that a first member 21 and a second member 22 are bonded via an adhesive layer 10, and is used for electric pulse peeling. According to the present disclosure, because the above-mentioned adhesive layer 10 is used, the adhesive strength of the adhesive layer 10 can be easily reduced by applying an electric pulse, making it possible to peel the first member 21 and the second member 22.

[0115] Each component of the laminate 20 of the present disclosure will be described in detail below. C-1. First Member and Second Member The first member 21 and second member 22 used in the present disclosure may be a conductor, an insulator, or a combination of a conductor and an insulator, but a conductor is preferred. This is because the effects of the present disclosure can be more effectively achieved. The conductor may be the same as the materials listed above as conductive materials. The first member 21 and second member 22 may be, for example, a steel plate formed using an iron alloy, or a plate-shaped member formed using a metal material such as aluminum or an aluminum alloy. The first member 21 and second member 22 may be a member formed by mixing and integrating particles of metals such as iron, copper, or aluminum, or alloys of these metals, with resin particles such as epoxy resin, polyimide, phenol melamine resin, urea unsaturated polyester resin, or alkyd polyurethane resin. The first member 21 and second member 22 may be members formed from different materials or the same material. An example of the first member 21 being made of different materials is one in which the first member 21 is made of steel and the second member 22 is made of an aluminum alloy plate.

[0116] The electrical resistivity (20°C) of the first member 21 and the second member 22 may be any value that can provide a desired reduction in adhesive strength. For example, the electrical resistivity may be 1.5×10 -8 Ω・m or more 1×10 4 It is preferably Ω·m or less, and 1×10 4 More preferably, it is 5×10 Ω·m or less. 3 It is even more preferable that the resistance is Ω·m or less, and 1×10 3 It is particularly preferable that the resistance is Ω·m or less.

[0117] C-2. Others The laminate 20 includes the first member 21, the second member 22, and the adhesive layer 10, but may also include other layers as necessary.

[0118] The laminate 20 may be used in applications where an electric pulse is applied to extract the first member 21 and the second member 22 and reuse them as recycled products. Such applications may be similar to those described in the section "A. Adhesive layer" above.

[0119] D. Method for Reducing Adhesive Strength Next, a method for reducing adhesive strength according to the present disclosure will be described. The method for reducing adhesive strength according to the present disclosure is characterized by including a step of applying an electric pulse to the laminate 20. The method for reducing adhesive strength according to the present disclosure is not particularly limited as long as it includes a step of applying an electric pulse to the laminate 20, but it is preferable to apply the electric pulse using a high-voltage pulse generator 30 as shown in FIG. 6.

[0120] D-1. Step of Applying Electric Pulses Electric pulses can be applied using a high-voltage pulse generator. Any known high-voltage pulse generator can be used as the high-voltage pulse generator. For example, the high-voltage pulse generator using a Marx booster circuit described in Japanese Patent Laid-Open Publication No. 56-139090 can be used as the high-voltage pulse generator.

[0121] As an example of a high-voltage pulse generator, as shown in FIG. 6 , a pair of electrodes (positive electrode 31 a and negative electrode 32 a) are connected to the output terminals of a high-voltage pulse generator 30 using cables 31 and 32, and the pair of electrodes (positive electrode 31 a and negative electrode 32 a) are arranged to connect to the first member 21 and the second member 22 of the laminate 20, respectively. When an electric pulse is applied from the high-voltage pulse generator 30 in this state, the electric pulse is applied to the adhesive layer 10 via the first member 21 and the second member 22. In FIG. 6 , the laminate 20 is fixed by a work table 40 having a base 41 and a pair of clamping tools 42 and 43 provided on the base 41. In addition, in FIG. 6 , the connection positions of the positive electrode 31 a and the negative electrode 32 a with the first member 21 and the second member 22 are positions that do not overlap with the adhesive layer 10 in a plan view.

[0122] As shown in Figure 7, the high-voltage pulse generator 30 is configured to charge a capacitor C from a DC power supply (charger) 33, and then switch a mechanical switch 34 to the discharge side (electrode side), thereby applying an electric pulse to the electrode in contact with the laminate 20, which is the object. By switching the mechanical switch between the charge side and the discharge side, charging and discharging are repeated, and it is possible to apply an electric pulse multiple times. Here, applying an electric pulse once means switching the switch from the charge side to the discharge side once.

[0123] As shown in Figure 6, in this process, the application position of the electric pulse, i.e., the connection position of a pair of electrodes (positive electrode 31a and negative electrode 31b) connected to a high-voltage pulse generator 30, may be the first member 21 and the second member 22 of the laminate, respectively, and may be a position that overlaps with the adhesive layer 10 in a planar view, or a position that does not overlap with the adhesive layer 10.

[0124] In this step, when the first member 21 and the second member 22 contain an insulator, the connection position is preferably close to the adhesive layer 10 in a planar view, preferably overlapping the adhesive layer 10 in a planar view, and preferably overlapping the first adhesive layer 10a in a planar view. In this step, when the adhesive layer 10 contains two or more first adhesive layers 10a and a first adhesive layer 10a exists as a target discharge location, the connection position is preferably overlapping the target first adhesive layer 10a in a planar view. This is because it becomes easier to induce discharge to the target first adhesive layer 10a when an electric pulse is applied.

[0125] The voltage applied by the electric pulse may be any voltage that can provide the adhesive layer 10 with a stable decrease in adhesive strength after application of the electric pulse, and is preferably 0.1 kV to 200 kV, more preferably 1 kV to 100 kV, even more preferably 10 kV to 80 kV, and most preferably 20 kV to 60 kV, because this allows the adhesive strength of the adhesive layer 10 to be more steadily decreased after application of the electric pulse.

[0126] The environment in which the electric pulse is applied may be any environment that can stably reduce the adhesive strength of the adhesive layer 10 after the electric pulse is applied, and may be a gas phase such as the atmosphere, or a liquid such as water. The gas phase may be a vacuum or reduced pressure environment. The atmosphere includes atmospheric pressure (1013.25 hPa) and pressures in the vicinity thereof, and may also include pressures within the range of normal atmospheric pressure changes. The atmospheric pressure may be, for example, in the range of 700 hPa or more and 1,300 hPa or less. In the present disclosure, the environment is preferably a gas phase, and more preferably the atmosphere, because this makes it easier to apply the electric pulse.

[0127] The temperature conditions for applying the electric pulse may be any conditions that allow the adhesive layer 10 to have a stable decrease in adhesive strength after application of the electric pulse, but are preferably −40° C. or higher and 150° C. or lower, more preferably −20° C. or higher and 100° C. or lower, and even more preferably −10° C. or higher and 50° C. or lower. This is because it allows the adhesive strength of the adhesive layer 10 to be more stably decreased after application of the electric pulse. The target of the temperature conditions may be the temperature of the adhesive layer 10 to which the electric pulse is applied.

[0128] When the environment in which the electric pulse is applied is in the gas phase, the relative humidity and temperature conditions in the gas phase may be such that the adhesive strength of the adhesive layer 10 can be stably reduced after the electric pulse is applied, and can be, for example, 1% RH or more and 99% RH or less.

[0129] The number of times the electric pulse is applied in this step may be one or more, and is preferably, for example, from one to 20 times, and more preferably from one to 10 times, because this makes it possible to more stably reduce the adhesive strength of the adhesive layer 10 after the application of the electric pulse.

[0130] In this step, the applied electric pulse has a voltage / current waveform with damped oscillation. The pulse width of the electric pulse, i.e., the interval between one cycle of the voltage and current waveforms, can be 1 ns to 100 ms, preferably 10 ns to 1 ms, more preferably 1 μs to 500 μs, and even more preferably 5 μs to 100 μs. This is because it enables the adhesive strength of the adhesive layer 10 to be reduced more stably after the electric pulse is applied.

[0131] The method of the present disclosure includes the step of applying the electric pulse, but may also include other steps as necessary, such as a fixing step of fixing the laminate 20 to the work table 40 before the step of applying the electric pulse, and an unfixing step of removing the laminate 20 from the work table 40 after the step of applying the electric pulse.

[0132] E. Manufacturing Method of Recycled Products Next, a manufacturing method of the recycled products of the present disclosure will be described. The manufacturing method of the recycled products of the present disclosure uses the above-mentioned method for reducing adhesive strength. Specifically, the manufacturing method includes a step of applying an electric pulse to a laminate 20 in which a first member 21 and a second member 22 are bonded via an adhesive layer 10, the adhesive layer 10 including a first adhesive layer 10a and a second adhesive layer 10b having a higher dielectric strength than the first adhesive layer 10a.

[0133] According to the present disclosure, the adhesive layer 10 described above is used in conjunction with an electric pulse, making it possible to easily manufacture recycled products.

[0134] The method for producing a recycled product according to the present disclosure includes a step of applying an electric pulse. Each step of the method for producing a recycled product according to the present disclosure will be described in detail below.

[0135] E-1. Step of applying an electric pulse This step is a step of applying an electric pulse to the laminate 20. The conditions for the electric pulse applied in this step are the same as those described in the above section "D. Method for reducing adhesive strength," and therefore, description thereof will be omitted here.

[0136] E-2. Other Steps The method for obtaining a recycled member according to the present disclosure includes the step of applying the electric pulse, but may also include other steps as necessary. Examples of such other steps include a separation step in which the first member 21 and the second member 22 are separated from the adhesive layer 10, whose adhesive strength has decreased after the step of applying the electric pulse, and a removal step in which the remaining portions of the adhesive layer 10 remaining on the first member 21 and the second member 22 after separation are removed. Examples of separation methods used in the separation step include manually or mechanically peeling the first member 21 and the second member 22 from the adhesive layer 10. The cleaning method used in the removal step may be any method capable of removing the remaining portions of the adhesive layer 10, such as manual removal, mechanical scraping, or dissolving and removing the remaining portions using a solvent.

[0137] F. Other The present disclosure includes the following aspects. [1] An adhesive layer comprising a first adhesive layer and a second adhesive layer having a higher dielectric strength than the first adhesive layer, and characterized by being used for electric pulse peeling. [2] The adhesive layer according to [1], characterized in that the absolute value of the difference between the dielectric strength of the first adhesive layer and the dielectric strength of the second adhesive layer is 0.1 kV / mm or more and 60 kV / mm or less. [3] The adhesive layer according to [1] or [2], characterized in that the dielectric strength of the first adhesive layer is in the range of 1 kV / mm or more and 60 kV / mm or less. [4] The adhesive layer according to any one of [1] to [3], characterized in that the first adhesive layer and the second adhesive layer have the same thickness. [5] The adhesive layer according to any one of [1] to [4], characterized in that the thickness of the first adhesive layer is 1 μm or more and 2 mm or less. [6] The adhesive layer according to any one of [1] to [4], characterized in that the thickness of the first adhesive layer is 1 μm or more and 2 mm or less. [7] The adhesive layer according to any one of [1] to [4], characterized in that the formation area of ​​the first adhesive layer is 1 mm or more. 2

[0013] The adhesive layer according to any one of [1] to [5], characterized in that the second adhesive layer is disposed adjacent to the entire periphery of the first adhesive layer. [7] The adhesive layer according to any one of [1] to [6], characterized in that the second adhesive layer is disposed adjacent to the entire periphery of the first adhesive layer. [8] The adhesive layer according to any one of [1] to [7], characterized in that the first adhesive layer is disposed 1 mm or more inward from the periphery of the adhesive layer. [9] The adhesive layer according to any one of [1] to [8], characterized in that the first adhesive layer contains a conductive material and a cured product of a resin component.

[10] The adhesive layer according to any one of [1] to [9], characterized in that the first adhesive layer is formed using a first curable composition containing a conductive material and a resin component.

[11] The adhesive layer according to [9] or

[10] , characterized in that the resin component contains at least one selected from an epoxy resin, an acrylic resin, and a urethane resin.

[12] The adhesive layer according to any one of [9] to

[11] , wherein the content of the conductive material is in the range of 0.05 parts by mass or more and 40 parts by mass or less per 100 parts by mass of the first adhesive layer.

[13] The adhesive layer according to any one of [9] to

[12] , wherein the particle size of the conductive material is in the range of 0.01 μm or more and 1000 μm or less.

[14] A laminate in which a first member and a second member are bonded via an adhesive layer, wherein the adhesive layer includes a first adhesive layer and a second adhesive layer having a higher dielectric strength than the first adhesive layer, and the laminate is used for electric pulse peeling.

[15] A curable composition including a conductive material and a resin component, wherein the curable composition includes a first adhesive layer and a second adhesive layer having a higher dielectric strength than the first adhesive layer, and is used to form the first adhesive layer of an adhesive layer used for electric pulse peeling.

[16] A set of curable compositions used for electric pulse stripping, comprising: a first curable composition containing a conductive material and a resin component; and a second curable composition that does not contain the conductive material or contains the conductive material in an amount less than that of the first curable composition, and a resin component.

[17] A method for reducing adhesive strength, comprising the step of applying an electric pulse to a laminate in which a first member and a second member are bonded via an adhesive layer, wherein the adhesive layer comprises a first adhesive layer and a second adhesive layer having a higher dielectric strength than the first adhesive layer.

[18] A method for manufacturing recycled products, comprising the step of applying an electric pulse to a laminate in which a first member and a second member are bonded via an adhesive layer, wherein the adhesive layer comprises a first adhesive layer and a second adhesive layer having a higher dielectric strength than the first adhesive layer.

[0138] The present disclosure is not limited to the above-described embodiments. The above-described embodiments are merely examples, and any configuration that is substantially identical to the technical idea described in the claims of the present disclosure and that provides similar effects is included within the technical scope of the present disclosure.

[0139] The present disclosure will be described in more detail below with reference to examples and comparative examples, but the present disclosure is not limited to these examples.

[0140] <Preparation of Curable Composition> Each component was placed in a container in the blending amounts shown in Table 1 below, and stirred with a spatula at 25°C for 5 minutes, followed by stirring using a planetary stirrer and further stirring using a roll kneader to prepare an adhesive composition.

[0141]

[0142] Carbon black (Acetylene Carbon Black, manufactured by Stem Chemicals, Inc., particle size: 42 nm, density: 1.8 g / cm) was used as a conductive material relative to 100 parts by mass of the obtained adhesive composition. 3 ) were added in the amounts shown in Table 2 below, and mixed using a roll mixer to prepare curable compositions 1 to 5 containing carbon black. Curable composition 6 contained only the adhesive composition without adding carbon black. In Table 2, the vol% of carbon black indicates the volume fraction of carbon black in the entire curable composition. In this example, the vol% of carbon black also indicates the volume fraction of carbon black in the adhesive layer formed using the curable composition.

[0143] <Measurement of Dielectric Strength> Two sheets of release tape (Nitto Denko Corporation; Nitoflon adhesive tape, width: 150 mm, thickness: 150 μm) were attached to a glass plate in the form of a frame surrounding a 50 mm × 50 mm square area. Next, the prepared curable compositions 1 to 6 were applied within the frame on the attached glass plate and cured at 180°C for 30 minutes to produce a 50 mm × 50 mm square cured film with a thickness of 300 μm. Next, the obtained cured film was sandwiched between two electrodes (circular, 25 mm diameter) in insulating oil (silicone), and a voltage was applied while increasing at a rate of 1 kV / s. The voltage at which the cured film broke down and a current of 100 mA was applied was taken as the dielectric breakdown voltage (kV). The dielectric strength (kV / mm) was calculated from the obtained dielectric breakdown voltage (kV) and the thickness of the cured film.

[0144]

[0145] Example 1 A laminate was fabricated with reference to JIS K 6850. Specifically, the surfaces of two identical steel plates (length: 100 mm, width: 25 mm, thickness: 16 mm, SPCC-SD 240 polished) were degreased with acetone. Next, as shown in FIG. 8( a), two 0.18 mm thick insulating tapes 23 (manufactured by Nitto Denko Corporation; Nitoflon adhesive tape width: 10 mm, thickness: 0.18 mm) were attached to one of the steel plates (first member 21). The first insulating tape 23 was applied so as to cover an area from 0 mm to 5 mm, with the insulating tape 23 extending 5 mm beyond the edge of the steel plate, and the second insulating tape 23 was applied 25 mm away from the edge of the first insulating tape 23 in the longitudinal direction of the steel plate, thereby defining an adhesive layer formation area 21a (a square measuring 25 mm in the longitudinal direction of the steel plate x 25 mm in the lateral direction of the steel plate) where the two insulating tapes 23 were arranged at both ends.

[0146] Next, a 0.18 mm high frame with a 5 mm x 5 mm square opening was placed so that the center of gravity of the adhesive layer formation region 21a was the center of the opening, and the inside of the opening was designated as the first adhesive layer formation region 21b (5 mm x 5 mm square). Next, curable composition 1 was applied to the opening to a thickness of 0.18 mm. As a result, the position of the first adhesive layer formation region 21b was formed so that the center of gravity of the first adhesive layer formation region 21b and the center of gravity of the adhesive layer formation region 21a were the same in a planar view. Next, the frame was removed, and curable composition 6 was applied to a thickness of 0.18 mm in the second adhesive layer formation region 21c, which is the portion of the adhesive layer formation region 21a other than the first adhesive layer formation region 21b.

[0147] Next, the other steel plate (second member 22) was placed on one of the steel plates (first member 21) so that the two steel plates overlapped only in the area where the insulating tape 23 was attached and the area where the curable composition was applied. Next, the overlapping steel plates were placed in a curing furnace, and the curable composition was cured at 180°C for 30 minutes, thereby producing a laminate 20 in which the two steel plates (first member 21 and second member 22) were bonded via the adhesive layer 10, as shown in the schematic diagram of Figure 9.

[0148] The laminate 20 still has the insulating tape 23 attached thereto, but the insulating tape 23 is omitted from FIG. 9 for ease of understanding.

[0149] Examples 2 to 5 A laminate 20 was produced in the same manner as in Example 1, except that the curable composition 1 used in the first adhesive layer 10a was changed to one shown in Table 3 below.

[0150] Examples 6 to 8 The laminate 20 was produced in the same manner as in Example 1, except that the planar shape of the first adhesive layer 10a was set as shown in the following Table 3. As in Example 1, the first adhesive layer-forming region 21b was positioned so that the center of gravity of the first adhesive layer-forming region 21b and the center of gravity of the adhesive layer-forming region 21a were the same in planar view.

[0151] [Comparative Examples 1 to 4] As shown in Figure 8 (b), insulating tape 23 was attached to a position 12.5 mm in the longitudinal direction from the end of the steel plate (first member 21), and an adhesive layer formation area (a rectangle measuring 12.5 mm in the longitudinal direction of the steel plate × 25 mm in the lateral direction of the steel plate) surrounded by the end of the steel plate and the insulating tape was set. Next, the entire surface of adhesive layer formation area 21a formed on the steel plate was designated as the first adhesive layer formation area, and curable compositions 1 to 4 were applied thereto, respectively. Laminates were produced in the same manner as in Example 1, except that a second adhesive layer formation area was not set.

[0152] Comparative Example 5 A laminate was produced in the same manner as in Comparative Example 1, except that the entire surface of the adhesive layer forming region 21a was used as the second adhesive layer forming region, and no first adhesive layer forming region was set.

[0153] <Application of Electric Pulse> Ten laminates each produced in Examples 1 to 8 and Comparative Examples 1 to 5 were prepared, and an electric pulse was applied to five of the laminates using the high-voltage pulse generator 30 described in FIG. 6 . As shown in FIG. 6 , using the laminate 20 as the target, a pair of electrodes (positive electrode 31 a and negative electrode 32 a) was connected to a steel plate (first member 21) and a steel plate (second member 22) joined via an adhesive layer 10. The connection positions of each electrode with the first member 21 and the second member 22 were approximately 50 mm away from the area where the adhesive layer 10 was formed, and were not overlapped with the adhesive layer 10 in a planar view. In addition, each of the electrodes was in contact with the surfaces of the first member 21 and the second member 22 opposite the area where the adhesive layer 10 was formed. Next, as shown in the circuit diagram of FIG. 7 , capacitor C was charged to 2.4 μF at a charging voltage of 35.4 kV using a DC power supply (charger) 33, and the circuit's mechanical switch 34 was switched to the electrode side (discharge side), thereby applying a single electric pulse to each electrode. The electric pulse was applied under conditions of 1 atmosphere, a temperature of 25°C, and a humidity of 60% RH. The voltage and current waveforms of the applied electric pulse were those with damped oscillations shown in FIG. 10 , with a pulse width of 20 μs per cycle and an oscillation convergence time of 320 μs.

[0154] [Evaluation] For the laminates to which an electric pulse was applied, the positions of discharge marks during the application of the electric pulse were observed, and the tensile strength (adhesion strength) was measured. In addition, of the 10 prepared laminates, 5 laminates to which no electric pulse was applied were also subjected to tensile strength measurements (n number: 5). 1. Internal Discharge Ratio After the application of the electric pulse (after the tensile shear test for laminates that did not completely peel), the presence or absence of discharge marks was visually observed for the laminates (n number: 5), and the ratio of discharge marks observed within the adhesive layer (ratio of internal discharge marks) was measured.

[0155] 2. Number of complete peels Regarding the laminates (n=5) after the application of the electric pulse, the number of laminates in which the first member and the second member were separated by only the application of the electric pulse was counted as the number of complete peels.

[0156] 3. Measurement of Tensile Strength (Adhesive Strength) A tensile shear test was conducted for each of the laminates of Examples 1 to 8 and Comparative Examples 1 to 5 in accordance with JIS K 6850. The tensile strength of the laminates (n number: 5) after application of an electric pulse and the tensile strength of the laminates (n number: 5) without application of an electric pulse were measured. Regarding the laminates after application of an electric pulse, only those that did not completely peel were measured. Specifically, for each laminate, one steel plate was pulled in the opposite direction to the other steel plate at 25°C and 5 mm / min using a universal testing machine (AGIS-100kN manufactured by Shimadzu Corporation). The tensile strength at the time when the two steel plates (first member 21 and second member 22) peeled, i.e., when the adhesive layer broke, was measured as the adhesive strength. The results are shown in Table 3 below. Adhesive strength before application (MPa): Average of n number: 5. Adhesion strength after application (MPa): represents the average value of the adhesive strength of the laminates that did not completely peel, and the difference from the average value to the maximum adhesive strength and the minimum adhesive strength. Average adhesive strength after application (MPa): represents the value obtained by dividing the total adhesive strength of the laminates that did not completely peel by the n number of 5. Adhesion strength reduction rate (%): represents a value expressed as average adhesive strength after application (MPa) / adhesive strength before application (MPa) × 100 (%). The higher the adhesive strength reduction rate, the more it can be determined that the adhesive strength of the adhesive layer can be stably reduced by applying an electric pulse.

[0157] 4. Appearance Observation For each of the laminates of Examples 1 to 8 and Comparative Examples 1 to 5, enlarged photographs of the side of each steel plate on which the adhesive layer was formed after the application of an electric pulse (after the tensile shear test for laminates that did not completely peel) are shown in (a) to (e) of Figures 11 to 23, respectively. The positions of the white circles in the upper photographs are internal discharge marks V, which indicate that internal discharge occurred within the adhesive layer. Photographs without white circles indicate that edge discharge rather than internal discharge occurred, or no discharge marks could be confirmed. Note that the white dotted lines in the enlarged photographs indicate the edge of the adhesive layer, and the areas surrounded by the white dotted lines in Figures 11 to 18 indicate the approximate location of the first adhesive layer.

[0158]

[0159] As shown in Table 3, it was confirmed that by using the adhesive layer of the example, an internal discharge can be generated within the first adhesive layer, and the adhesive strength of the adhesive layer can be stably reduced by applying an electric pulse.

[0160] The adhesive layer of the present disclosure can be used to dismantle home appliances, mobile communication terminals, and the like that are no longer in use due to breakdowns or changes in the product life cycle.

[0161] REFERENCE SIGNS LIST 10 adhesive layer 10a first adhesive layer 10b second adhesive layer 20 laminate 21 first member 21a adhesive layer forming area 21b first adhesive layer forming area 21c second adhesive layer forming area 22 second member 23 insulating tape 30 high voltage pulse generator 31, 32 cable 31a positive electrode 32a negative electrode 33 DC power supply (charger) 34 mechanical switch 40 workbench 41 base 42, 43 clamping tool V internal discharge trace

Claims

1. An adhesive layer comprising a first adhesive layer and a second adhesive layer having a higher dielectric strength than the first adhesive layer, characterized in that the adhesive layer is used for electric pulse peeling.

2. The adhesive layer described in claim 1, characterized in that the absolute value of the difference between the dielectric strength of the first adhesive layer and the dielectric strength of the second adhesive layer is within the range of 0.1 kV / mm or more and 60 kV / mm or less.

3. The adhesive layer according to claim 1, characterized in that the dielectric strength of the first adhesive layer is 1 kV / mm or more and 60 kV / mm or less.

4. The adhesive layer according to claim 1, wherein the first adhesive layer and the second adhesive layer have the same thickness.

5. The adhesive layer according to claim 1, wherein the first adhesive layer comprises a conductive material and a cured product of a resin component.

6. The adhesive layer according to claim 5, wherein the resin component contains at least one resin selected from the group consisting of epoxy resins, acrylic resins, and urethane resins.

7. The adhesive layer according to claim 5, characterized in that the content of the conductive material is 0.05 parts by mass or more and 40 parts by mass or less per 100 parts by mass of the first adhesive layer.

8. The adhesive layer of claim 1, wherein the second adhesive layer is disposed adjacent to the entire periphery of the first adhesive layer.

9. A laminate in which a first member and a second member are bonded via an adhesive layer, the adhesive layer comprising a first adhesive layer and a second adhesive layer having a higher dielectric strength than the first adhesive layer, characterized in that the laminate is used for electric pulse peeling.

10. A curable composition comprising a conductive material and a resin component, the curable composition comprising a first adhesive layer and a second adhesive layer having a higher dielectric strength than the first adhesive layer, the curable composition being used to form the first adhesive layer of an adhesive layer used in electric pulse peeling.

11. A method for manufacturing recycled products, comprising the step of applying an electric pulse to a laminate in which a first member and a second member are bonded via an adhesive layer, wherein the adhesive layer comprises a first adhesive layer and a second adhesive layer having a higher dielectric strength than the first adhesive layer.

12. A method for reducing adhesive strength, comprising the step of applying an electric pulse to a laminate in which a first member and a second member are bonded via an adhesive layer, wherein the adhesive layer comprises a first adhesive layer and a second adhesive layer having a higher dielectric strength than the first adhesive layer.

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