Method for dismantling adhesive structures

Abstract

The present invention provides a means for easily dismantling a structure constructed by adhesion, without leaving any adhesive residue on the surface of the adherend and without requiring a large load to peel off the adhesive surface. [Solution] The present invention relates to a method for disassembling an adhesive structure having a first adherend, a second adherend, and an adhesive layer disposed between the first adherend and the second adherend, comprising a peeling step of heating the adhesive structure at a temperature of 60°C to 120°C to peel the adhesive layer from at least one of the first adherend and the second adherend, wherein the adherend is made of at least one material selected from the group consisting of heat-treated aluminum alloy, titanium, and magnesium alloy, and the adhesive layer comprises a cured product of an adhesive that is curable at room temperature and has a glass transition temperature of 60°C to 120°C.

Description

Technical Field

[0001] The present invention relates to a method for disassembling an adhesive structure having two adherends adhered by an adhesive layer.

Background Art

[0002] Room temperature curing two-component adhesives are used when repairing automobile parts, etc. However, such adhesives have the property of being highly viscous and having poor wettability at the adhesive interface from the viewpoint of workability such as preventing dripping. Therefore, usually in order to ensure strength, as a pretreatment for adhesion, the surface of an adherend made of metal or the like is roughened with sandpaper or the like and cleaned by degreasing or the like. On the other hand, since room temperature curing two-component adhesives have high interfacial adhesion, when disassembling a joint such as for repair, it is necessary to physically remove the adhesive remaining on the surface. Also, since the adherends are joined on the surface, a large load needs to be applied to peel off the adhered adherends, and thus disassembling is difficult.

[0003] By the way, in recent years, from the viewpoint of resource conservation, various products and their parts are required to have parallel recyclability, and the ease of disassembly is also required for products and parts manufactured by adhesive bonding.

[0004] In order to enhance the bonding strength during use, room temperature curing two-component adhesives are generally used such that the adhesion force at the adhesive interface is stronger than the cohesive force of the adhesive. However, then the adhesive remains on the surface of the adherend. Therefore, efforts have been made to impart easy disassembly to products and parts adhered with the adhesive.

[0005] Japanese Patent Publication No. 2002-201457 (Patent Document 1) discloses an easily peelable curable adhesive characterized by using a crosslinkable polymer as an active ingredient, having a viscosity of 15 to 100,000 mPa·s at 25°C before curing and a glass transition temperature of 30°C or less lower than the peel temperature after curing. However, in the technology of Patent Document 1, the adhesive force at the adhesive interface is higher than the adhesive cohesive force, so there is a risk that adhesive residue will remain at the interface of the adherend. In fact, the examples in Patent Document 1 describe adhesive residue adhering to adherends that are not intended for reuse.

[0006] Japanese Patent Publication No. 2012-107309 (Patent Document 2) discloses an aluminum alloy substrate having a surface oxide film formed on the surface of the aluminum alloy substrate, and further having an adhesive layer made of an adhesive on the surface of the surface oxide film. According to Patent Document 2, an aluminum alloy plate with excellent adhesive durability is provided, in which interfacial delamination at the bonding interface of the adhesive is less likely to occur, and therefore the adhesive strength is less likely to decrease. The disclosure in Patent Document 2 provides an aluminum alloy plate with excellent adhesive durability, and does not impart easy disassembly to products or parts bonded with adhesive.

[0007] Japanese Patent Publication No. 7-252687 (Patent Document 3) discloses a method for bonding titanium and titanium alloys, which involves forming an oxide film on the surface of titanium and titanium alloys, and then reducing the oxide film to form a hardened metallic layer. According to the method in Patent Document 3, the adhesive strength of the adhesive can be significantly increased. However, the method disclosed in Patent Document 3 does not impart easy disassembly to products or parts bonded with the adhesive.

[0008] Japanese Patent Publication No. 2024-045802 (Patent Document 4) describes how an epoxy adhesive and a detachable fastener are used in combination to achieve high adhesive strength during use, but to reduce the adhesive strength of the adhesive layer during dismantling, a guide path is provided to introduce a medium that generates a moist atmosphere (such as heated steam), thereby wetting the adhesive and reducing its adhesive strength, thus achieving easy dismantling.

[0009] Patent Document 4 requires a structure that delivers heated steam specifically to the adhesive, necessitating a steam supply during disassembly. Furthermore, while Patent Document 4 proposes applications to battery cases, in the case of batteries, there is a risk of runaway reactions due to short circuits caused by water ingress. Additionally, since epoxy adhesives remain on the adherend, surface polishing of the adherend is required during re-adhesion. The technology in Patent Document 4 requires the use of heated steam as a means of swelling the adhesive, making its application to water-reactive products dangerous and creating structural constraints.

[0010] Japanese Patent Publication No. 2022-106811 (Patent Document 5) reports an adhesive that, by incorporating a crosslinkable polymer with a special structure, is normally used by curing it at low temperatures, but during demolition, it can be further heated to become a high-crosslink density polymer, making it possible to peel the adhesive from the interface. Patent Document 5 achieves high strength and easy demolition by incorporating a limited number of crosslinkable polymers. However, because the structure of the crosslinkable polymer incorporated into the adhesive is special, it becomes difficult to control the workability such as application and bonding of the adhesive. In addition, because it is necessary to expose it to a high-temperature environment during demolition, the entire bonded area must be heated to a high temperature, which restricts the objects to be bonded and the equipment used during demolition. [Prior art documents] [Patent Documents]

[0011] [Patent Document 1] Japanese Patent Publication No. 2002-201457 [Patent Document 2] Japanese Patent Publication No. 2012-107309 [Patent Document 3] Japanese Patent Application Publication No. 7-252687 [Patent Document 4] Japanese Patent Publication No. 2024-045802 [Patent Document 5] Japanese Patent Publication No. 2022-106811 [Overview of the project] [Problems that the invention aims to solve]

[0012] As described above, the easily peelable curing adhesive disclosed in Patent Document 1 may leave adhesive residue on the surface of the adherend. The methods of applying an oxide film to the surface of a metal described in Patent Documents 2 and 3 cannot provide easy disassembly to products or parts bonded with adhesive. The means of providing easy disassembly to products or parts bonded with adhesive disclosed in Patent Documents 4 and 5 have many limitations. Therefore, the present invention aims to provide a means for easily disassembling a structure constructed by adhesive without leaving any cured adhesive residue on the surface of the adherend and without requiring a large load to peel off the bonded surface. [Means for solving the problem]

[0013] To solve the above problems, the inventors conducted intensive research. As a result, the inventors discovered that an adhesive structure having two adherends bonded together with an adhesive having a glass transition temperature of 60°C to 120°C can be peeled off at the interface without cohesive failure of the cured adhesive by heating it at a temperature of 60°C to 120°C.

[0014] In other words, the present invention encompasses the following aspects and embodiments. (Embodiment 1) A method for dismantling an adhesive structure having a first adherend, a second adherend, and an adhesive layer disposed between the first adherend and the second adherend, A peeling process in which the adhesive structure is heated to a temperature of 60°C to 120°C to peel the adhesive layer from at least one of the first adherend and the second adherend. Includes, The adherend consists of at least one material selected from the group consisting of heat-treated aluminum alloy, titanium, and magnesium alloy. The adhesive layer has room-temperature curing properties and includes a cured product of an adhesive having a glass transition temperature of 60°C to 120°C. The aforementioned method. (Embodiment 2) The method according to Embodiment 1, wherein the adhesive layer contains a cured product of a two-component mixed epoxy-based, acrylic-based, or urethane-based adhesive. (Embodiment 3) The method according to Embodiment 1 or 2, wherein the adherend is made of a 6000 series aluminum alloy heat-treated at a high temperature. (Embodiment 4) The method according to any one of Embodiments 1 to 3, wherein the bonded structure is produced by bonding a first adherend and a second adherend that have not been subjected to a pretreatment for roughening the surface, and an adhesive layer. (Embodiment 5) The bonded structure further has a fastening member that sandwiches the first adherend and the second adherend. A fastening member removing step of removing the fastening member from the bonded structure before the peeling step. "" The method according to any one of Embodiments 1 to 4, further comprising the above. (Embodiment 6) The method according to any one of Embodiments 1 to 5, further comprising applying an external force in the peeling step. (Embodiment 7) The method according to Embodiment 6, wherein the external force is applied by inserting a chisel. [[ID=?6]](Embodiment 8) The method according to Embodiment 4, wherein a degreasing treatment is performed as a pretreatment other than the pretreatment for roughening the surface. (Embodiment 9) The method according to Embodiment 5, wherein the fastening member is a bolt and a nut or a screw. ?

Advantages of the Invention

[0015] According to the present invention, it is possible to provide a means for disassembling a structure constituted by adhesion without leaving an adhesive on the surface of the adherend and without applying a large load when peeling the bonded surface.

Brief Description of the Drawings

[0016] ) [Figure 1] It is a flowchart showing each step in the method for disassembling the bonded structure of the present invention. [Figure 2] Figure 2A is a schematic diagram showing one aspect of the adhesive structure of the present invention during normal use, where the adhesion is further reinforced by attaching fastening members to the adhesive structure. Figure 2B is a schematic diagram showing one aspect of the adhesive structure of the present invention during disassembly. In the adhesive structure of the present invention, two adherends are bonded together by an adhesive layer. During disassembly, fastening members such as bolts and nuts are removed, and the adherends are separated from the adhesive layer by heating to 60°C to 120°C. If necessary during separation, external force is applied by inserting a chisel or the like. The separated adherends are then recovered. [Modes for carrying out the invention]

[0017] Preferred embodiments of the present invention will be described in detail below.

[0018] The present invention relates to a method for disassembling an adhesive structure having a first adherend, a second adherend, and an adhesive layer disposed between the first adherend and the second adherend. The method of the present invention includes a peeling step of heating the adhesive structure at a temperature of 60°C to 120°C to peel the adhesive layer from at least one of the first adherend and the second adherend, wherein the adherend is made of at least one material selected from the group consisting of heat-treated aluminum alloy, titanium, and magnesium alloy, and the adhesive layer includes a cured product of an adhesive that is curable at room temperature and has a glass transition temperature of 60°C to 120°C.

[0019] (1) Definition In this specification, "adhesive structure" means a structure having a structure in which multiple adherends are bonded to each other by an adhesive layer. An adhesive structure typically comprises a first adherend, a second adherend, and an adhesive layer disposed between the first adherend and the second adherend.

[0020] A typical adhesive structure in the present invention is a structure in which two adherends are bonded together by an adhesive layer placed between them. In this specification, the two adherends are referred to as the "first adherend" and the "second adherend," respectively, in order to distinguish them. However, the adhesive structure of the present invention is not limited to such a form, and the present invention also encompasses adhesive structures having two or more adherends, such as a structure having three adherends in which a third adherend is bonded to the second adherend by an adhesive layer, or a structure having four adherends in which a fourth adherend is bonded to the third adherend by an adhesive layer.

[0021] In this specification, "adhered material" refers to the main material that forms the adhesive structure as defined herein, and consists of multiple layers bonded together by an adhesive layer.

[0022] In this specification, "adhesive layer" refers to a layer containing a cured adhesive that bonds multiple adherends together.

[0023] In this specification, "room temperature" refers to a temperature range of 10°C to 30°C.

[0024] In this specification, "glass transition temperature" refers to the temperature at which the cured adhesive contained in the adhesive layer transitions from a solid state to a liquid state.

[0025] In this specification, "fastening member" means a member in the adhesive structure of the present invention that has the effect of strengthening the adhesion between two adherends bonded together by an adhesive layer.

[0026] (2) The peeling process of the present invention The method of the present invention includes, as an essential step, a peeling step (step S1) in which the adhesive structure is peeled off by heating it at a temperature of 60°C to 120°C. The method of the present invention may optionally include an adhesive structure fabrication step (step S0) in which two adherends are bonded together with an adhesive layer to produce an adhesive structure (Figure 1).

[0027] Because the cured adhesive contained in the adhesive layer of the present invention is hardened at room temperature, the two adherends are bonded together via the adhesive layer before the peeling process. The cured adhesive contained in the adhesive layer liquefies when heated to its glass transition temperature, so the adherends are peeled off at the adhesive interface without causing cohesive failure of the cured adhesive. In other words, because the cured adhesive contained in the adhesive layer of the present invention has a glass transition temperature of 60°C to 120°C, it is possible to peel the bonded structure at the interface by heating it to a temperature of 60°C to 120°C. This makes it possible to easily dismantle the bonded structure bonded by the adhesive layer without leaving any cured adhesive residue on the surface of the adherends. The bonded adherends are then recovered, and since no cured adhesive residue remains on the surface of the recovered adherends, they have high reusability.

[0028] The adherend in this invention is at least one material selected from the group consisting of heat-treated aluminum alloys, titanium, and magnesium alloys, preferably a heat-treated aluminum alloy, and particularly preferably a 6000 series aluminum alloy that has been heat-treated at a high temperature (T5 or higher). Heat treatment is not required for titanium and magnesium alloys.

[0029] As described above, the adhesive layer of the present invention has room-temperature curing properties and includes a cured product of an adhesive having a glass transition temperature of 60°C to 120°C. Suitable cured products to be included in the adhesive layer of the present invention include, but are not limited to, cured products of two-component epoxy, acrylic, or urethane adhesives.

[0030] (3) Fastening member removal process In the present invention, in order to mechanically strengthen the adhesion of the adherends, the adhesive structure may further include fastening members that sandwich the first adherend and the second adherend (Figure 2A). In that case, a fastening member removal step is performed to remove the fastening members from the adhesive structure before the peeling step (Figure 2B, schematic diagram in the upper section). Examples of such fastening members include bolts and nuts or screws.

[0031] Furthermore, in the present invention, an external force may be applied during the peeling process, in which the materials are heated to a temperature of 60°C to 120°C, thereby promoting the separation of the adherends (Figure 2B, schematic diagram in the middle). An example of a means for applying an external force is to insert a chisel between the first adherend and the second adherend.

[0032] This allows for easier dismantling of the bonded structure, which is bonded by the adhesive layer, and recovery of the detached adherend, without leaving any cured adhesive residue on the surface of the adherend (Figure 2B, schematic diagram in the lower section). As mentioned in (2) above, this has the advantage that no adhesive residue remains on the surface of the recovered adherend.

[0033] (4) Pretreatment of the substrate Preferably in the present invention, the first adherend and the second adherend of the adhesive structure are bonded to the adhesive layer without any surface roughening pretreatment.

[0034] As described in the section on prior art, in this field, surface roughening pretreatment such as sanding with sandpaper has been performed to increase the strength of adhesion by adhesives. However, the adhesive structure of the present invention is manufactured by bonding the first adherend and the second adherend to the adhesive layer without performing such surface roughening pretreatment. Examples of pretreatment other than surface roughening in the present invention include degreasing and chemical etching, with degreasing being particularly preferred. The advantage of not performing surface roughening pretreatment on the adhesive is that it is not necessary to apply a large load to peel off the adhesive. [Examples]

[0035] The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples.

[0036] (Examples 1-2, Comparative Example 1) Shear test specimens were prepared as described below, and shear-tensile tests were performed on these specimens to observe the fracture load and failure mode.

[0037] As the adherend, we used #6061-T6 extruded aluminum alloy (manufactured by UACJ), measuring 25 mm in width, 100 mm in length, and 1.0 mm in thickness, which had been heat-treated at high temperatures (treated with T6). The adherend was subjected to the following three types of pretreatment. (1) Degreasing treatment (Example 1) (2) Chemical etching treatment (immersion in alkaline solution / acid solution) (Example 2) (3) Roughening by #80 sandpaper polishing (10 polishes in each of the four directions with a load of 3 kg) (Comparative Example 1)

[0038] After the above pretreatment was performed on the substrate, SikaPower880 (manufactured by SIKA), a two-component, room-temperature curing epoxy adhesive, was applied to an area measuring 25 mm in width, 10 mm in length, and 0.15 mm in thickness, and cured at room temperature for 3 days.

[0039] The samples prepared in this manner were used as shear test specimens, and shear tensile tests were performed under the following test conditions. Temperature: 80°C, Tensile test speed: 5 mm / min, Chuck distance: 100 mm

[0040] The test results are shown in Table 1. When degreasing (Example 1) and chemical etching (Example 2) were performed as pretreatment, 100% of the cured adhesive material peeled off at the interface. However, when roughening by sandpaper polishing (Comparative Example 1) was performed, 100% of the cured adhesive material underwent cohesive failure. In other words, when pretreatment other than surface roughening, such as degreasing and chemical etching, was performed, unlike the pretreatment by sandpaper polishing, the cured adhesive material could be peeled off at the interface without cohesive failure.

[0041] [Table 1]

[0042] (Comparative Example 2) A steel plate (SPC270) measuring 25 mm wide x 100 mm long x 1.6 mm thick was used as the adherend. The adherend was degreased as a pretreatment. SikaPower880 (manufactured by SIKA), a two-component, room-temperature curing epoxy adhesive, was applied to the pretreated adherend over an area measuring 25 mm wide x 10 mm long x 0.15 mm thick, and cured at room temperature for 3 days. The sample prepared in this manner was used as a shear test specimen, and a shear tensile test was performed under the following test conditions. Temperature: 80°C, Tensile test speed: 5 mm / min, Chuck distance: 100 mm

[0043] As a result, at a maximum load of 2000N (8MPa), 100% cohesive failure occurred in the cured adhesive. Therefore, when the adherend was a steel plate, interfacial delamination of the cured adhesive was not possible.

[0044] (Comparative Example 3) As the adherend, an unheated aluminum alloy #6061 measuring 25 mm wide x 100 mm long x 1.0 mm thick was used. The adherend was degreased as a pretreatment. SikaPower880 (manufactured by SIKA), a two-component room-temperature curing epoxy adhesive, was applied to the pretreated adherend in an area measuring 25 mm wide x 10 mm long x 0.15 mm thick, and cured at room temperature for 3 days. The sample prepared in this manner was used as a shear test specimen, and a shear tensile test was performed under the following test conditions. Temperature: 80°C, Tensile test speed: 5 mm / min, Chuck distance: 100 mm

[0045] As a result, at a maximum load of 1420N (5.7MPa), the adhesive underwent 100% cohesive failure. Therefore, when the adherend was unheat-treated aluminum alloy #6061, interfacial delamination of the adhesive was not possible.

[0046] (Comparative Examples 4-5) As the adherend, a 25mm wide x 100mm long x 1.0mm thick extruded aluminum alloy #6061-T6 (manufactured by UACJ), heat-treated at high temperature (treated with T6), was used. The adherend was degreased as a pretreatment. SikaPower880 (manufactured by SIKA), a two-component room-temperature curing epoxy adhesive, was applied to the pre-treated adherend in an area of ​​25mm wide x 10mm long x 0.15mm thick, and cured at room temperature for 3 days. The sample prepared in this manner was used as a shear test specimen, and a shear tensile test was performed under the following test conditions. (1) Temperature: 23°C, Tensile test speed: 5 mm / min, Chuck distance: 100 mm (Comparative Example 4) (2) Temperature: 40°C, Tensile test speed: 5 mm / min, Chuck distance: 100 mm (Comparative Example 5)

[0047] Under the test conditions of Comparative Example 4, 100% cohesive failure of the cured adhesive occurred at a maximum load of 4000 N (16 MPa). Therefore, when the test temperature was 23°C, interfacial delamination of the cured adhesive was not possible.

[0048] Under the test conditions of Comparative Example 5, 100% cohesive failure of the cured adhesive occurred at a maximum load of 3600 N (14.4 MPa). Therefore, when the test temperature was 40°C, interfacial delamination of the cured adhesive was not possible.

[0049] (Example 3) As the adherend, an aluminum alloy #6061-T6 (manufactured by UACJ) measuring 25 mm in width, 100 mm in length, and 1.0 mm in thickness, which had been heat-treated at high temperature (T6 treatment), was used. As a pretreatment, the adherend was degreased. SikaPower880 (manufactured by SIKA), a two-component room-temperature curing epoxy adhesive, was applied to the pre-treated adherend in an area measuring 25 mm in width, 10 mm in length, and 0.15 mm in thickness, and cured at room temperature for 3 days. The sample prepared in this manner was used as a shear test specimen, and a shear tensile test was performed under the following test conditions. Temperature: 100℃, Tensile test speed: 5mm / min, Chuck distance: 100mm

[0050] As a result, at a maximum load of 1100N (4.4MPa), 100% of the cured adhesive delaminated at the interface. Therefore, when the adherend was heated to 100°C and a shear test tensile test was performed, the cured adhesive could be delaminated at the interface.

[0051] It should be noted that the present invention is not limited to the embodiments described above, and various modifications are included. For example, the embodiments described above are described in detail to make the present invention easier to understand, and are not necessarily limited to those having all the configurations described. In addition, it is possible to add, delete, and / or replace some of the configurations in each embodiment with other configurations.

Claims

1. A method for dismantling an adhesive structure having a first adherend, a second adherend, and an adhesive layer disposed between the first adherend and the second adherend, A peeling step in which the adhesive structure is heated to a temperature of 60°C to 120°C to peel the adhesive layer from at least one of the first adherend and the second adherend. Includes, The adherend consists of at least one material selected from the group consisting of heat-treated aluminum alloy, titanium, and magnesium alloy. The adhesive layer has room-temperature curing properties and includes a cured product of an adhesive having a glass transition temperature of 60°C to 120°C. The aforementioned method.

2. The method according to claim 1, wherein the adhesive layer comprises a cured product of a two-component epoxy, acrylic, or urethane adhesive.

3. The method according to claim 1, wherein the adherend is made of a 6000 series aluminum alloy that has been heat-treated at a high temperature.

4. The method according to claim 1, wherein the adhesive structure is made by bonding a first adherend and a second adherend, which have not undergone surface roughening pretreatment, to an adhesive layer.

5. The adhesive structure further includes fastening members that sandwich the first adherend and the second adherend. The fastening member removal process is performed before the peeling process, in which the fastening member is removed from the adhesive structure. The method according to claim 1, further comprising:

Images