Adhesive composition and method of making same, structural adhesive and use thereof

Abstract

The present disclosure relates to an adhesive composition, a preparation method thereof, a structural adhesive and applications thereof. The adhesive composition comprises an adhesive resin, magnetic nanoparticles and expandable microparticles, wherein the magnetic nanoparticles are Mn x Zn 1‑x Fe2O4, x is 0.6-0.9; the content of the adhesive resin is 60-95 parts by weight, the content of the magnetic nanoparticles is 2-30 parts by weight, and the content of the expandable microparticles is 2-30 parts by weight, based on 100 parts by weight of the adhesive composition. The adhesive composition of the present disclosure can rapidly generate heat under the action of an alternating magnetic field, effectively improve the efficiency and safety of the adhesive disassembly process, and meet the requirements of green environmental protection.

Description

Technical Field

[0001] This disclosure relates to an adhesive composition and its preparation method, structural adhesives and their applications. Background Technology

[0002] Currently, most new energy power battery packs use CTP (Cell to Pack) technology to replace mechanical assembly, which can eliminate or reduce intermediate modules, thereby increasing pack energy density, reducing pack cost, and reducing assembly steps. However, the CTP structure requires a large amount of adhesive to connect and fix the cells. In order to ensure safety and reliability during vehicle use, the adhesive must have sufficient strength, which also causes great trouble for subsequent battery pack maintenance and recycling.

[0003] Power battery packs using CTP (Cell-to-Pack) technology are often replaceable, not repairable, and replacing the entire pack is extremely expensive. Furthermore, existing packs can only be disassembled using force, which is extremely costly in terms of manpower and resources, and poses potential safety risks. The disassembled cells are generally scrapped, resulting in inefficient resource utilization.

[0004] Currently, the alternative to forceful disassembly is to use adhesive release agents, such as reducing solutions, to break the bond between adjacent structural components. This usually requires soaking the battery pack in the adhesive release agent for several days to complete the process, which is slow, generates pollutants, and is very environmentally unfriendly. Summary of the Invention

[0005] The purpose of this disclosure is to provide a highly efficient and environmentally friendly adhesive composition, a method for preparing the same, a structural adhesive, and its applications.

[0006] To achieve the above objectives, in a first aspect, this disclosure provides an adhesive composition comprising an adhesive resin, magnetic nanoparticles, and expandable microparticles, wherein the magnetic nanoparticles are Mn x Zn 1-x Fe2O4, x is 0.6~0.9; based on 100 parts by weight of the adhesive composition, the content of the adhesive resin is 60~95 ​​parts by weight, the content of the magnetic nanoparticles is 2~30 parts by weight, and the content of the expandable microparticles is 2~30 parts by weight.

[0007] Optionally, based on 100 parts by weight of the adhesive composition, the content of the resin is 70 to 90 parts by weight, the content of the magnetic nanoparticles is 5 to 15 parts by weight, and the content of the expandable microparticles is 5 to 15 parts by weight.

[0008] Optionally, the magnetic nanoparticles are Mn 0.7 Zn 0.3Fe2O4 and / or Mn 0.8 Zn 0.2 Fe2O4.

[0009] Optionally, the magnetic nanoparticles have a particle size of 10-100 nm; and / or, the expandable microparticles have a particle size of 10-60 μm.

[0010] Optionally, the magnetic nanoparticles comprise first magnetic nanoparticles with a particle size of 10-30 nm and second magnetic nanoparticles with a particle size of 30-50 nm, wherein the weight ratio of the first magnetic nanoparticles to the second magnetic nanoparticles is 1:(0.5-2); and / or,

[0011] The expandable microparticles include a first expandable microparticle with a particle size of 10~25μm and a second expandable microparticle with a particle size of 25~40μm, and the weight ratio of the first expandable microparticle to the second expandable microparticle is 1:(0.5~2).

[0012] Optionally, the expandable microparticle has a core-shell structure, wherein the core particle size of the expandable microparticle is 5~30μm and the outer shell thickness is 5~30μm.

[0013] Optionally, the shell material of the expandable microparticles includes at least one selected from polyacrylonitrile-methyl acrylate copolymer, polyacrylonitrile-methyl methacrylate copolymer, polyvinylidene chloride-methyl acrylate copolymer, and polyvinylidene chloride-methyl methacrylate copolymer; and / or,

[0014] The core material of the expandable particles includes at least one of C1-C6 alkanes, C2-C6 alkenes, and C2-C6 alkynes.

[0015] Optionally, the adhesive resin includes at least one of polyurethane resin, epoxy resin, acrylic resin, and silicone resin.

[0016] A second aspect of this disclosure provides a method for preparing the adhesive composition described in the first aspect of this disclosure, the method comprising:

[0017] An adhesive composition is obtained by mixing adhesive resin, magnetic nanoparticles and expandable microparticles.

[0018] The mixing conditions include: a temperature of 40-60 °C and a vacuum degree of 10. -5 ~10Pa, time is 1~6 h.

[0019] A third aspect of this disclosure provides a structural adhesive comprising the adhesive composition described in the first aspect of this disclosure and an optional curing agent.

[0020] This disclosure provides a fourth aspect, which provides the application of the structural adhesive described in the third aspect of this disclosure in new energy power battery packs.

[0021] Through the above technical solution, the adhesive composition disclosed herein includes an adhesive resin, magnetic nanoparticles, and expandable microparticles. Under the action of an alternating magnetic field, the expandable microparticles can be triggered to expand, reducing the adhesive strength and thus meeting the requirement for easy disassembly of the adhesive, which is beneficial for resource recycling. Furthermore, by employing special magnetic nanoparticles Mn... x Zn 1- x Fe2O4 is a material with excellent magnetic heating efficiency. It can generate heat rapidly under the action of an alternating magnetic field, thereby effectively improving the efficiency and safety of the adhesive disassembly process and meeting the requirements of green environmental protection.

[0022] Other features and advantages of this disclosure will be described in detail in the following detailed description section. Detailed Implementation

[0023] The following provides a detailed description of specific embodiments of this disclosure. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit this disclosure.

[0024] In a first aspect, this disclosure provides an adhesive composition comprising an adhesive resin, magnetic nanoparticles, and expandable microparticles, wherein the magnetic nanoparticles are Mn x Zn 1-x Fe2O4, x is 0.6~0.9; based on 100 parts by weight of the adhesive composition, the content of the adhesive resin is 60~95 ​​parts by weight, the content of the magnetic nanoparticles is 2~30 parts by weight, and the content of the expandable microparticles is 2~30 parts by weight.

[0025] This disclosure provides an adhesive material with easily removable properties under specific conditions by combining adhesive resin, magnetic nanoparticles, and expandable microparticles. The magnetic nanoparticles generate heat under an alternating magnetic field, heating the composition in situ and triggering the expandable microparticles to expand, reducing the adhesive strength and thus meeting the requirement for easy disassembly. This facilitates resource recycling and effectively improves the efficiency and safety of the adhesive disassembly process, complying with green environmental protection requirements. This composition is designed to meet the requirements for the removability of adhesive connection structures, and is particularly suitable for applications requiring disassembly and recycling, such as the CTP (Cell to Pack) structure in new energy power battery packs, enabling rapid and non-destructive disassembly of the battery pack without the need for large industrial equipment for baking.

[0026] In a preferred embodiment, based on 100 parts by weight of the adhesive composition, the content of the adhesive resin is 70-90 parts by weight, the content of the magnetic nanoparticles is 5-15 parts by weight, and the content of the expandable microparticles is 5-15 parts by weight. Meeting the above-mentioned preferred component ratio is beneficial for further improving disassembly efficiency.

[0027] According to this disclosure, the magnetic nanoparticles are Mn x Zn 1-x Fe2O4, with x of 0.6~0.9, exhibits excellent magnetic heating efficiency, rapidly heating under an alternating magnetic field. This thermal effect can be precisely controlled, ensuring heating uniformity and efficiency. In a preferred embodiment, the magnetic nanoparticles are Mn. 0.7 Zn 0.3 Fe2O4 and / or Mn 0.8 Zn 0.2 Fe2O4, the aforementioned material, has excellent magnetic heating efficiency, which is beneficial for further improving disassembly efficiency.

[0028] Further, the average particle size of the magnetic nanoparticles can be 10-100 nm, preferably 10-50 nm. In a preferred embodiment, the magnetic nanoparticles may include a first magnetic nanoparticle with a particle size of 10-30 nm and a second magnetic nanoparticle with a particle size of 30-50 nm, wherein the weight ratio of the first magnetic nanoparticle to the second magnetic nanoparticle can be 1:(0.5-2). This combination of two types of magnetic nanoparticles with different particle sizes is beneficial for improving the dispersibility of the magnetic nanoparticles in the composition, enabling more uniform and efficient heating under the action of an alternating magnetic field, thereby enhancing the overall magnetocaloric effect.

[0029] According to this disclosure, the expandable microparticles can expand under the heating effect of magnetic nanoparticles, causing the adhesive to expand structurally as a whole. This significantly weakens the adhesive's strength and bonding force, making the structural components easier to disassemble. The particle size of the expandable microparticles can be adjusted within a certain range; specifically, the average particle size of the expandable microparticles can be 10~60 μm, preferably 10~40 μm. In a preferred embodiment, the expandable microparticles may include a first expandable microparticle with a particle size of 10~25 μm and a second expandable microparticle with a particle size of 25~40 μm. The weight ratio of the first expandable microparticle to the second expandable microparticle can be 1:(0.5~2). By combining expandable microparticles of different particle sizes, thermal expansion effects under different alternating magnetic field conditions can be achieved, improving disassembly efficiency.

[0030] In one specific embodiment, the expandable microparticles are a core-shell structure encapsulating volatile hydrocarbons in thermoplastic resin. Preferably, the outer shell material of the expandable microparticles includes at least one of polyacrylonitrile-methyl acrylate copolymer, polyacrylonitrile-methyl methacrylate copolymer, polyvinylidene chloride-methyl acrylate copolymer, and polyvinylidene chloride-methyl methacrylate copolymer. The core material of the expandable microparticles includes at least one of C1-C6 alkanes (such as n-pentane, hexane, etc.), C2-C6 olefins (such as ethylene, propylene, etc.), and C2-C6 alkynes (such as acetylene, propyne, etc.). Expandable microparticles obtained using the above materials have excellent expansion performance, which is beneficial to improving disassembly efficiency while reducing environmental impact.

[0031] Furthermore, by adjusting the core particle size and outer shell thickness of the expandable microparticles, precise control of the expansion ratio can be achieved, further improving disassembly efficiency. Specifically, the core particle size of the expandable microparticles can be 5~30 μm, and the outer shell thickness of the expandable microparticles can be 5~30 μm.

[0032] According to this disclosure, the adhesive resin may include at least one of polyurethane resin, epoxy resin, acrylic resin, and silicone resin. These materials possess excellent comprehensive properties and are particularly suitable for applications requiring high strength and durability, such as automobiles. The weight-average molecular weight of the resin can be adjusted within a wide range, specifically from 50,000 to 1,000,000.

[0033] The adhesive composition disclosed herein is particularly suitable for the CTP structure of new energy power battery packs. By using this composition, on the one hand, the strength of the adhesive will not decrease drastically within the normal operating temperature range of the battery, meeting reliability requirements; on the other hand, the battery pack can be easily disassembled by applying an alternating magnetic field at an appropriate location, eliminating the need for mechanical force or chemical solvents, thus improving disassembly efficiency and safety, and meeting green environmental protection requirements. Since the adhesive can be disassembled without damaging the connecting components, these components can be more efficiently recycled and reused, contributing to improved resource utilization efficiency and promoting green and sustainable development.

[0034] A second aspect of this disclosure provides a method for preparing the adhesive composition described in the first aspect of this disclosure, the method comprising: mixing an adhesive resin, magnetic nanoparticles, and expandable microparticles to obtain an adhesive composition; wherein the mixing conditions include: a temperature of 40-60 °C and a vacuum degree of 10. -5 The conditions of ~10 Pa and 1~6 h will not cause the expandable particles to expand, and at the same time, they are conducive to the uniform dispersion of the particles in the composition.

[0035] In a preferred embodiment, the method further includes pretreating the magnetic nanoparticles before mixing to prevent them from agglomerating in the adhesive composition. The pretreatment may include: placing the magnetic nanoparticles in deionized water and dispersing the agglomerates under water bath conditions; then adding oleic acid, stirring under heating conditions for a certain time, and finally washing with ethanol and separating the oleic acid-coated magnetic nanoparticles using a permanent magnet.

[0036] A third aspect of this disclosure provides a structural adhesive comprising the adhesive composition described in the first aspect of this disclosure and an optional curing agent.

[0037] The type of curing agent is not particularly limited and can be selected according to the type of adhesive resin in the adhesive composition. For example, when polyurethane resin is used as the adhesive resin, the curing agent can be selected accordingly, such as polyisocyanate. The amount of curing agent can be adjusted within a certain range, specifically according to the type and amount of adhesive resin. The weight ratio of the curing agent to the adhesive composition can be (1~6):1, preferably (2~4):1.

[0038] The structural adhesive disclosed herein has the same beneficial effects as the adhesive compositions described above, which will not be repeated here.

[0039] This disclosure provides a fourth aspect, which provides the application of the structural adhesive described in the third aspect of this disclosure in new energy power battery packs.

[0040] Specifically, the new energy power battery pack includes the structural adhesive, and the application may include disassembling the new energy power battery pack under the action of an alternating magnetic field. The strength of the alternating magnetic field can be 60~200eO.

[0041] The present disclosure is further described in detail below through examples.

[0042] Example 1

[0043] The weight percentages of each component in the adhesive composition of this embodiment are as follows: 85 wt.% polyurethane resin (weight average molecular weight of 100,000), 10 wt.% Mn 0.7 Zn 0.3 Fe2O4 magnetic nanoparticles (average particle size 20 nm), 5 wt.% expandable microparticles (average particle size 25 μm); wherein, the outer shell of the expandable microparticles is made of polyacrylonitrile-methyl acrylate copolymer with a thickness of 15 μm, and the core is acetylene gas with a particle size of 10 μm.

[0044] The manufacturing process is as follows: polyurethane resin, magnetic nanoparticles and expandable microparticles are mixed, heated to 60°C, and stirred for 1 hour under a vacuum of 10 Pa. Then, the mixture is cooled to room temperature and sealed for storage.

[0045] Example 2

[0046] The adhesive composition was prepared according to the method of Example 1, except that the components and their weight percentages are as follows: 70 wt.% epoxy resin (weight average molecular weight of 100,000), 15 wt.% Mn 0.7 Zn 0.3 Fe2O4 magnetic nanoparticles (average particle size 10 nm), 15 wt.% expandable microparticles (average particle size 10 μm); wherein, the outer shell of the expandable microparticles is made of polyvinylidene chloride-methyl acrylate copolymer with a thickness of 5 μm, and the core is propyne gas with a core particle size of 5 μm.

[0047] Example 3

[0048] The adhesive composition was prepared according to the method of Example 1, except that the components and their weight percentages are as follows: 90 wt.% acrylic resin (weight average molecular weight of 150,000), 5 wt.% Mn 0.7 Zn 0.3 Fe2O4 magnetic nanoparticles (average particle size 50 nm), 5 wt.% expandable microparticles (average particle size 40 μm); wherein, the outer shell of the expandable microparticles is made of polyacrylonitrile-methyl methacrylate copolymer with a thickness of 30 μm, and the core is propylene gas with a particle size of 30 μm.

[0049] Example 4

[0050] The adhesive composition was prepared according to the method of Example 1, except that the magnetic nanoparticles were Mn. 0.8 Zn 0.2 Fe2O4 (average particle size is 20 nm).

[0051] Example 5

[0052] The adhesive composition was prepared according to the method of Example 1, except that the magnetic nanoparticles were Mn. 0.6 Zn 0.4 Fe2O4 (average particle size is 20 nm).

[0053] Example 6

[0054] The adhesive composition was prepared according to the method of Example 1, except that the magnetic nanoparticles included Mn with a particle size of 10-30 nm. 0.7 Zn 0.3Fe2O4 and Mn with a particle size of 30~50 nm 0.7 Zn 0.3 Fe2O4, the weight ratio of the two is 1:1.

[0055] Example 7

[0056] The adhesive composition was prepared according to the method of Example 1, except that the expandable microparticles were a first expandable microparticle with a particle size of 10-25 μm and a second expandable microparticle with a particle size of 25-40 μm; wherein the outer shell material of the first expandable microparticle and the second expandable microparticle were both polyacrylonitrile-methyl acrylate copolymer, and the core material of both were acetylene gas; the outer shell thickness of the first expandable microparticle was 5-10 μm, and the core particle size was 5-15 μm; the outer shell thickness of the second expandable microparticle was 15-20 μm, and the core particle size was 10-20 μm.

[0057] Example 8

[0058] The adhesive composition was prepared according to the method of Example 1, except that the components and their weight percentages are as follows: 60 wt.% polyurethane resin, 20 wt.% Mn 0.7 Zn 0.3 Fe2O4 magnetic nanoparticles, 20wt.% expandable microparticles.

[0059] Example 9

[0060] The adhesive composition was prepared according to the method of Example 1, except that the components and their weight percentages are as follows: 95 wt.% polyurethane resin, 2 wt.% Mn 0.7 Zn 0.3 Fe2O4 magnetic nanoparticles, 3 wt.% expandable microparticles.

[0061] Example 10

[0062] The adhesive composition was prepared according to the method of Example 1, except that Mn 0.7 Zn 0.3 The average particle size of Fe2O4 magnetic nanoparticles is 100 nm, and the average particle size of expandable microparticles is 60 μm.

[0063] Comparative Example 1

[0064] The adhesive composition was prepared according to the method of Example 1, except that the same amount of Mn was used. 0.5 Zn 0.5 Fe2O4 (average particle size 20 nm) was used as a magnetic nanoparticle to replace Mn. 0.7 Zn 0.3 Fe2O4.

[0065] Comparative Example 2

[0066] The adhesive composition was prepared according to the method of Example 1, except that the same amount of nano-Fe3O4 (average particle size of 60 nm) was used as magnetic nanoparticles to replace Mn. 0.7 Zn 0.3 Fe2O4.

[0067] Test case

[0068] The adhesive compositions of the examples and comparative examples were prepared as structural adhesives and their performance was tested. Specifically, the adhesive composition was thoroughly mixed with an optional amount of curing agent in a clean container. A region was marked at one end of the wide side of the aluminum strip with a blade to define the overlapping surface. The overlapping surface of the aluminum strip was wiped with a clean cloth dampened with 95% alcohol to remove dust, oil, and other impurities. The alcohol-cleaned surface was allowed to dry for at least 10 minutes. The mixed adhesive was applied to the overlapping surface of the aluminum strip. After the adhesive was smoothed, the strips were quickly overlapped and pressed together, and the two ends of the overlapping surface were fixed with clips. It was important to keep the two aluminum strips on the same horizontal line. The adhesive layer thickness was 0.2 mm, and the operation time was controlled between 20 and 40 minutes. After complete curing, the strips were left at room temperature for 7 days, and then subsequent performance tests were conducted. The results are listed in Table 1.

[0069] Magnetic field heating temperature test method: Place the sample under a 120 oE AC magnetic field for 5 min, use an infrared thermometer to test the temperature of the structural adhesive, and record the results. Each group of samples was tested three times, and the average value was taken.

[0070] Tensile shear test: Following GB / T 7124-2008, the specimen was cured in a constant temperature and humidity chamber (25℃ / 50%RH) for at least 7 days before testing. The specimen was clamped in a fixture, with the distance from the clamping point to the nearest bonded end being 50 mm ± 1 mm. A tensile testing machine was used to apply tension at a rate of 5 mm / min, and the curve was recorded. The maximum stress during failure is the failure load F (N), divided by the bonded area A (mm²). 2 The tensile shear strength δ (MPa) is obtained as follows: δ = F / A. The tensile shear strength at 25℃ and magnetic heating temperature is tested in a temperature-controlled chamber. At least three sets of samples are required for each test, following the requirements for tensile shear testing described above. The sample is placed in a universal tensile testing machine with a temperature-controlled chamber for at least 30 minutes until a constant temperature is reached before testing. During the test, the door needs to be opened and closed for a certain period to maintain a constant sample temperature. The average value is taken. The difference in shear strength is calculated using the following formula:

[0071] Shear strength at Δδ=25℃ - Shear strength at magnetic heating temperature

[0072] Table 1

[0073]

[0074] As shown in Table 1, under the same alternating magnetic field conditions, compared with the comparative example, the adhesive composition of the embodiment can achieve a higher magnetic heating temperature, rapidly reduce the shear strength of the structural adhesive, and has high disassembly efficiency.

[0075] The preferred embodiments of this disclosure have been described in detail above. However, this disclosure is not limited to the specific details of the above embodiments. Within the scope of the technical concept of this disclosure, various simple modifications can be made to the technical solutions of this disclosure, and these simple modifications all fall within the protection scope of this disclosure.

[0076] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, this disclosure will not describe the various possible combinations separately.

[0077] Furthermore, various different embodiments of this disclosure can be combined in any way, as long as they do not violate the spirit of this disclosure, they should also be regarded as the content disclosed in this disclosure.

Claims

1. An adhesive composition, characterized in that, The adhesive composition comprises an adhesive resin, magnetic nanoparticles, and expandable microparticles, wherein the magnetic nanoparticles are Mn x Zn 1-x Fe2O4, x is 0.6~0.9; based on 100 parts by weight of the adhesive composition, the content of the adhesive resin is 70~90 parts by weight, the content of the magnetic nanoparticles is 5~15 parts by weight, and the content of the expandable microparticles is 5~15 parts by weight; the average particle size of the magnetic nanoparticles is 10~50 nm, and the average particle size of the expandable microparticles is 10~40 μm; the expandable microparticles have a core-shell structure, the outer shell material of the expandable microparticles includes at least one of polyacrylonitrile-methyl acrylate copolymer, polyacrylonitrile-methyl methacrylate copolymer, and polyvinylidene chloride-methyl acrylate copolymer, the core material of the expandable microparticles includes at least one of C1~C6 alkanes, C2~C6 olefins, and C2~C6 alkynes, and the adhesive resin includes at least one of polyurethane resin, epoxy resin, and acrylic resin.

2. The adhesive composition according to claim 1, wherein, The magnetic nanoparticles are Mn 0.7 Zn 0.3 Fe2O4 and / or Mn 0.8 Zn 0.2 Fe2O4.

3. The adhesive composition according to claim 1, wherein, The magnetic nanoparticles comprise first magnetic nanoparticles with a particle size of 10-30 nm and second magnetic nanoparticles with a particle size of 30-50 nm, wherein the weight ratio of the first magnetic nanoparticles to the second magnetic nanoparticles is 1:(0.5-2); and / or, The expandable microparticles include a first expandable microparticle with a particle size of 10~25μm and a second expandable microparticle with a particle size of 25~40μm, and the weight ratio of the first expandable microparticle to the second expandable microparticle is 1:(0.5~2).

4. The adhesive composition according to claim 1, wherein, The core particle size of the expandable microparticle is 5~30μm, and the outer shell thickness of the expandable microparticle is 5~30μm.

5. A method for preparing the adhesive composition according to any one of claims 1 to 4, characterized in that, The method includes: An adhesive composition is obtained by mixing adhesive resin, magnetic nanoparticles and expandable microparticles. The mixing conditions include: a temperature of 40-60 °C and a vacuum degree of 10. -5 ~10Pa, time is 1~6 h.

6. A structural adhesive, characterized in that, It includes the adhesive composition according to any one of claims 1 to 4 and an optional curing agent.

7. The application of the structural adhesive as described in claim 6 in new energy power battery packs.

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