A flame-retardant detachable carbon dioxide-based polyurethane heat-conducting structural adhesive as well as a preparation method and application thereof

Abstract

The application provides a kind of flame-retardant detachable carbon dioxide-based polyurethane heat-conducting structural adhesive and its preparation method and application, the polyurethane heat-conducting structural adhesive includes component A and component B, the component A includes the following raw materials: carbon dioxide copolymer polyol 15-40 parts;Structure regulator 1-5 parts;First heat-conducting filler 70-90 parts;Expandable microsphere 1-5 parts;The component B includes the following raw materials: polyurethane prepolymer 10-20 parts;Isocyanate 5-15 parts;Second heat-conducting filler 70-90 parts;Water-removing agent 1-5 parts.The polyurethane heat-conducting structural adhesive of the application not only has the characteristics of raw materials environmental protection, energy saving, renewable, but also has excellent bonding performance, high thermal conductivity, flame retardant and thermal detachability, can meet the demand of power battery pack structure bonding, heat conduction, flame retardant, can also meet the demand of battery disassembly and recycling.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of polyurethane adhesives, and particularly relates to a flame-retardant detachable carbon dioxide-based polyurethane heat-conducting structural adhesive as well as a preparation method and application thereof. BACKGROUND

[0002] Carbon dioxide is a rich and cheap renewable carbon source. The research field of preparing carbon dioxide-based high molecular polymers from carbon dioxide has made important progress. The carbon dioxide copolymer polyols prepared from carbon dioxide and propylene oxide have the structural characteristics of coexisting carbonate-ether bonds, can replace traditional polyester and polyether polyols to prepare polyurethanes with excellent performance, and the byproduct propylene carbonate in the process can be further utilized to achieve full utilization of the product. The small molecule carbon dioxide-based polyols prepared by ring-opening reaction of propylene carbonate can be used as small molecule chain extenders for polyurethanes, providing an important direction for the development of polyurethane materials.

[0003] With the rapid development of electronic equipment, new energy vehicles and other fields, the performance requirements of polyurethane structural adhesives are also getting higher and higher. Traditional polyurethane structural adhesives often cannot meet the requirements in applications requiring high thermal conductivity, such as battery packaging of new energy vehicles, heat dissipation of electronic equipment, etc., and are difficult to disassemble after bonding and packaging, leading to difficulties in equipment maintenance or battery recycling. Therefore, it is urgent to develop an environmentally friendly polyurethane structural adhesive with high thermal conductivity, easy disassembly, excellent bonding performance and flame retardancy for the heat-conducting structural bonding of new energy batteries by using carbon dioxide-based polyols. SUMMARY

[0004] In view of the deficiencies of the prior art, the purpose of the present application is to provide a flame-retardant detachable carbon dioxide-based polyurethane heat-conducting structural adhesive as well as a preparation method and application thereof.

[0005] To achieve this purpose, the technical solutions adopted by the present application are as follows:

[0006] On the one hand, the present application provides a flame-retardant detachable carbon dioxide-based polyurethane heat-conducting structural adhesive, which comprises component A and component B. The component A comprises the following raw materials in parts by mass:

[0007]

[0008] The component B comprises the following raw materials:

[0009]

[0010] In the present application, the polyurethane heat-conductive structural adhesive prepared from the carbon dioxide copolymer polyol contains a large number of strong polar carbonate groups in the molecular structure, effectively improving the bonding strength of the heat-conductive structural adhesive; the high content of carbonate groups makes the material release a large amount of carbon dioxide to isolate oxygen during combustion decomposition, thereby increasing the flame-retardant effect in cooperation with the flame retardant; at the same time, the structural regulator and the expandable microspheres are used, and the hydrogen bonds between the structural regulator and the polyurethane molecules and the volume expansion of the expandable microspheres occur at elevated temperatures, respectively, reducing the intermolecular force of the polyurethane and the contact area between the heat-conductive structural adhesive and the bonded part, thereby reducing the bonding strength and achieving the purpose of the polyurethane heat-conductive structural adhesive being detachable.

[0011] In the present application, the content of the carbon dioxide copolymer polyol in the preparation raw material of the A component can be 15 parts, 18 parts, 20 parts, 23 parts, 25 parts, 28 parts, 30 parts, 33 parts, 35 parts, 38 parts or 40 parts; but not limited to the listed values, other values not listed within the value range are also applicable.

[0012] In the present application, the content of the structural regulator in the preparation raw material of the A component can be 1 part, 2 parts, 3 parts, 4 parts or 5 parts; but not limited to the listed values, other values not listed within the value range are also applicable.

[0013] In the present application, the content of the first heat-conductive filler in the preparation raw material of the A component can be 70 parts, 73 parts, 75 parts, 78 parts, 80 parts, 83 parts, 85 parts, 88 parts or 90 parts; but not limited to the listed values, other values not listed within the value range are also applicable.

[0014] In the present application, the content of the expandable microspheres in the preparation raw material of the A component can be 1 part, 2 parts, 3 parts, 4 parts or 5 parts; but not limited to the listed values, other values not listed within the value range are also applicable.

[0015] Preferably, the carbon dioxide copolymer polyol is one or a combination of at least two of the polypropylene carbonate polyols copolymerized from carbon dioxide as a raw material and propylene oxide under the action of an initiator and a catalyst.

[0016] Preferably, the molecular weight of the carbon dioxide copolymer polyol is 500-8000 g / mol, for example 500 g / mol, 800 g / mol, 1000 g / mol, 2000 g / mol, 3000 g / mol, 4000 g / mol, 5000 g / mol, 6000 g / mol, 7000 g / mol or 8000 g / mol.

[0017] Preferably, the hydroxyl functionality of the carbon dioxide copolymer polyol is 2-5, for example 2, 3, 4 or 5.

[0018] Preferably, the molar fraction of intramolecular carbonate groups of the carbon dioxide copolymer polyol is 0.25 to 0.45, for example 0.25, 0.28, 0.30, 0.35, 0.38, 0.40, or 0.45.

[0019] Preferably, the structure regulator is a monohydric alcohol monomer having an electron- donating group with a nitrogen heteroatom.

[0020] Preferably, the structure regulator is selected from one or a combination of at least two of N-hydroxyethyl-2-pyrrolidone, 2-hydroxyethylpyridine, N-hydroxyethylpyrrolidine, 3-hydroxymethylpyrrolidine, 2-hydroxymethylpyrrolidine, 1 -methyl-3-pyrrolidinol, or N-hydroxyethylpiperidine.

[0021] Preferably, the first thermally conductive filler is one or a combination of at least two of aluminum hydroxide, aluminum oxide, or boron nitride.

[0022] Preferably, the expandable microspheres are low temperature expandable microspheres.

[0023] Preferably, the expandable microspheres are selected from one or a combination of at least two of Nouryon’s 031 DU 40, 053 DU 40, 043 DU 80, or Japan Matsumoto Gomu Pharmaceutical Co.’s F-48 or F-50.

[0024] Preferably, the A component further comprises a coupling agent.

[0025] Preferably, the coupling agent is selected from one or a combination of at least two of gamma-glycidoxypropyltrimethoxysilane, gamma-(2,3 epoxypropoxy)propyltrimethoxysilane, ureidopropyltriethoxysilane, beta-(3,4 epoxy cyclohexyl)-ethyltrimethoxysilane, gamma-ureidopropyltrimethoxysilane.

[0026] Preferably, the coupling agent is present in the A component in an amount of 1 to 2 parts, for example 1 part, 1.3 parts, 1.5 parts, 1.6 parts, 1.8 parts, or 2 parts.

[0027] Preferably, the A component further comprises a catalyst.

[0028] Preferably, the catalyst is selected from one or a combination of at least two of organobismuth, organozinc, dibutyltin dilaurate.

[0029] Preferably, the catalyst is present in the A component in an amount of 0.02 to 0.1 parts, for example 0.02 parts, 0.05 parts, 0.08 parts, or 0.1 parts.

[0030] In this invention, the content of polyurethane prepolymer in component B can be 10 parts, 13 parts, 15 parts, 18 parts, or 20 parts; the content of isocyanate can be 5 parts, 7 parts, 9 parts, 10 parts, 12 parts, 14 parts, or 15 parts; the content of the second thermally conductive filler can be 70 parts, 73 parts, 75 parts, 78 parts, 80 parts, 83 parts, 85 parts, 88 parts, or 90 parts; and the content of dehydrating agent can be 1 part, 2 parts, 3 parts, 4 parts, or 5 parts.

[0031] Preferably, the polyurethane prepolymer is obtained by reacting carbon dioxide copolymer polyol, small molecule carbon dioxide-based polyol and isocyanate.

[0032] Preferably, the small molecule carbon dioxide-based polyol is a product obtained by reacting propylene carbonate with an aliphatic polyamine.

[0033] Preferably, the aliphatic polyamine is any one or a combination of at least two of ethylenediamine, cyclohexanediamine, tris(2-aminoethyl)amine, tris(3-aminopropyl)amine, diethylenetriamine, triethylenetetramine, or tetraethylenepentamine.

[0034] Preferably, the molecular weight of the small molecule carbon dioxide-based polyol is 200-700 g / mol, for example, 200 g / mol, 250 g / mol, 300 g / mol, 380 g / mol, 400 g / mol, 500 g / mol, 600 g / mol or 700 g / mol.

[0035] Preferably, the functionality of the small molecule carbon dioxide-based polyol is 2 to 3.

[0036] Preferably, the molar fraction of intramolecular carbonate groups in the small molecule carbon dioxide-based polyol is 0.25 to 0.45, for example, 0.25, 0.28, 0.30, 0.35, 0.38, 0.40 or 0.45.

[0037] In this invention, the propylene carbonate can be a byproduct of the synthesis of polypropylene carbonate polyol, or it can be prepared by the ring-opening reaction of carbon dioxide and propylene oxide.

[0038] Preferably, in the raw materials for preparing the polyurethane prepolymer, the mass ratio of carbon dioxide copolymer polyol to small molecule carbon dioxide-based polyol is 100:(5-20); for example, 100:5, 100:8, 100:10, 100:12, 100:14, 100:15, 100:17, 100:18, 100:19 or 100:20. In this invention, if the mass proportion of small molecule carbon dioxide-based polyol is too large, the viscosity of the prepolymer will be too high, making it inconvenient to produce; if the mass proportion of small molecule carbon dioxide-based polyol is too small, the prepolymer will have poor performance and low strength.

[0039] Preferably, the polyurethane prepolymer is prepared by mixing carbon dioxide copolymer polyol and small molecule carbon dioxide-based polyol evenly, removing water, and then adding isocyanate to react and obtain the polyurethane prepolymer.

[0040] In this invention, a polyurethane prepolymer is obtained by reacting carbon dioxide copolymer polyol, small molecule carbon dioxide-based polyol, and isocyanate. Its molecular structure contains a large number of highly polar carbonate groups, which further effectively improves the bonding strength of the thermally conductive structural adhesive.

[0041] Preferably, the dehydration is performed by vacuum dehydration at 100-120°C (e.g., 100°C, 105°C, 108°C, 110°C, 115°C, 118°C or 120°C) for 2-3 hours (e.g., 2 hours, 2.3 hours, 2.5 hours, 2.8 hours or 3 hours).

[0042] Preferably, after dehydration, the temperature is lowered to 40–60°C (e.g., 40°C, 43°C, 45°C, 50°C, 55°C, or 60°C), and isocyanate is added under nitrogen protection to carry out the reaction.

[0043] Preferably, the temperature for adding isocyanate to react is 80-90°C (e.g., 80°C, 83°C, 85°C, 88°C or 90°C), and the reaction time is 2-3 hours (e.g., 2 hours, 2.3 hours, 2.5 hours, 2.8 hours or 3 hours).

[0044] In this invention, the isocyanate is one or a combination of at least two of diphenylmethane diisocyanate and polyphenylmethylene polyisocyanate.

[0045] Preferably, the second thermally conductive filler is one or a combination of at least two of aluminum hydroxide, aluminum oxide, or boron nitride.

[0046] Preferably, the dehydrating agent is one or a combination of at least two of molecular sieve activated powder and p-toluenesulfonyl isocyanate.

[0047] Preferably, the volume ratio of component A to component B is 1:0.8 to 1.2, for example, 1:0.8, 1:0.9, 1:1, 1:1.1 or 1:1.2.

[0048] Secondly, the present invention provides a method for preparing the flame-retardant, detachable carbon dioxide-based polyurethane thermally conductive structural adhesive as described above, the method comprising the following steps:

[0049] (1) Add carbon dioxide copolymer polyol and first thermally conductive filler into the reactor, remove water, cool down, then add expandable microspheres, structure regulator, optional coupling agent and optional catalyst, and mix evenly under vacuum to obtain component A;

[0050] (2) The polyurethane prepolymer, isocyanate, second thermally conductive filler and dehydrating agent are added into the reactor and mixed and degassed under vacuum to obtain component B.

[0051] Preferably, the dehydration in step (1) is performed by vacuum dehydration at 110-120°C (e.g., 110°C, 115°C, 118°C or 120°C) for 2-3 hours (e.g., 2 hours, 2.3 hours, 2.5 hours, 2.8 hours or 3 hours).

[0052] Preferably, the cooling is to a temperature of 40–60°C (e.g., 40°C, 43°C, 45°C, 50°C, 55°C, or 60°C).

[0053] Preferably, the expandable microspheres in step (1) are expandable microspheres that have been freeze-dried.

[0054] Thirdly, the present invention provides the application of the flame-retardant, removable carbon dioxide-based polyurethane thermally conductive structural adhesive as described above in the bonding of thermally conductive structures in new energy batteries.

[0055] Compared with the prior art, the present invention has the following beneficial effects:

[0056] In this invention, a polyurethane thermally conductive structural adhesive prepared using carbon dioxide copolymer polyol contains a large number of highly polar carbonate groups in its molecular structure, which effectively improves the adhesive strength. The high content of carbonate groups allows the material to release a large amount of carbon dioxide during combustion and decomposition, isolating oxygen and thus synergistically enhancing the flame-retardant effect with the flame retardant. Simultaneously, a structure modifier and expandable microspheres are used. The hydrogen bonds formed between the structure modifier and polyurethane molecules, and the expansion of the microspheres, undergo hydrogen bond breakage and volume expansion respectively when the temperature is increased, reduce the intermolecular forces of polyurethane and the contact area between the thermally conductive structural adhesive and the bonded parts, thereby reducing the adhesive strength and achieving the purpose of making the polyurethane thermally conductive structural adhesive removable.

[0057] The polyurethane thermally conductive structural adhesive of the present invention not only has the characteristics of environmentally friendly, energy-saving and renewable raw materials, but also has excellent bonding performance, high thermal conductivity, flame retardancy and thermal disassembly, which can meet the requirements of bonding, thermal conductivity and flame retardancy of power battery pack structure, and can also meet the requirements of battery disassembly and recycling. Detailed Implementation

[0058] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0059] Example

[0060] This embodiment provides a flame-retardant, detachable carbon dioxide-based polyurethane thermally conductive structural adhesive and its preparation method. The preparation method includes the following steps:

[0061] The carbon dioxide copolymer polyol and the first thermally conductive filler were mixed and heated to 110°C, then vacuum dehydrated for 3 hours, cooled to 50°C, and then other components were added and mixed evenly under vacuum to obtain component A.

[0062] The second thermally conductive filler was pre-dried under vacuum at 110°C and then cooled. Subsequently, it was added to the reactor along with the polyurethane prepolymer, isocyanate, and dehydrating agent and mixed under vacuum to remove bubbles, thus obtaining component B.

[0063] The volume ratio of component A to component B is 1:1, and the raw material composition ratio is shown in Table 1.

[0064] In component A, the hydroxyl value of carbon dioxide copolymer polyol 1 is 100±2 mgKOH / g, and its functionality is 2 (PCD-211, Huizhou Daya Bay Dazhi Fine Chemical Co., Ltd.); the hydroxyl value of carbon dioxide copolymer polyol 2 is 224±20 mgKOH / g, and its functionality is 2 (ETERNACOLL, Ube Industries, Ltd.). PH-50);

[0065] In component A, structure modifier 1 is 2-hydroxyethylpyridine, structure modifier 2 is N-hydroxyethylpyrrolidine, and structure modifier 3 is 2-hydroxymethylpyrrolidine.

[0066] The expandable microspheres in component A are F-48 from Matsumoto Oils & Fats Co., Ltd., Japan.

[0067] The first thermally conductive filler in component A is aluminum hydroxide.

[0068] The coupling agent in component A is γ-glycidoxypropyltrimethoxysilane.

[0069] The catalyst in component A is an organic bismuth-zinc catalyst complex.

[0070] In component B, the polyurethane prepolymer is obtained by reacting carbon dioxide copolymer polyol, small molecule carbon dioxide-based polyol and isocyanate. The preparation method is as follows: the carbon dioxide copolymer polyol and small molecule carbon dioxide-based polyol are mixed at a mass ratio of 10:1 and dehydrated under vacuum at 110°C for 3 hours. Then, the temperature is lowered to 50°C, and under nitrogen protection, isocyanate is added and heated to 90°C for 3 hours to obtain isocyanate-terminated polyurethane prepolymer 1 with a molar ratio of NCO to OH of 5:1.

[0071] The carbon dioxide copolymer polyol is polypropylene carbonate diol with a molecular weight of 2000 (PCD-621 from Huizhou Daya Bay Dazhi Fine Chemical Co., Ltd.); the small molecule carbon dioxide-based polyol is prepared by the ring-opening reaction of propylene carbonate and diethylenetriamine with a molecular weight of 400 and a functionality of 3; the isocyanate is a mixture of diphenylmethane diisocyanate and polyphenylmethylene polyisocyanate with a mixing mass ratio of 4:1.

[0072] The method for preparing small molecule carbon dioxide-based polyols is as follows: a specified amount of propylene carbonate is placed in a three-necked flask, and then heated to the reaction temperature. Under nitrogen protection, a specified amount of diethylenetriamine is added dropwise and the reaction is carried out. The reaction is carried out at 90°C for 6 hours to obtain small molecule carbon dioxide-based polyols, wherein the molar ratio of propylene carbonate to diethylenetriamine is 3:1.

[0073] The isocyanate in component B is polyphenyl polymethylene polyisocyanate.

[0074] The second thermally conductive filler in component B is aluminum hydroxide.

[0075] The dehydrating agent in component B is 3A molecular sieve activated powder, which is produced by Jiangxi Xintao Technology Co., Ltd.

[0076] Table 1

[0077]

[0078] Comparative Example 1

[0079] A detachable polyurethane thermally conductive structural adhesive and its preparation method are disclosed. The only difference from Example 1 is that the polyol of component A is polyether polyol PPG1000 (a commercially available product), as shown in Table 2.

[0080] Comparative Example 2

[0081] A detachable polyurethane thermally conductive structural adhesive and its preparation method differ from Example 1 only in that the polyol of component A is polyether polyol PPG1000 (commercially available product) and the proportions of each component raw material are different, as shown in Table 2.

[0082] Comparative Example 3

[0083] A detachable polyurethane thermally conductive structural adhesive and its preparation method are disclosed. The only difference from Example 1 is that expandable microspheres are not added to component A, as shown in Table 2.

[0084] Comparative Example 4

[0085] A detachable polyurethane thermally conductive structural adhesive and its preparation method are disclosed. The only difference from Example 1 is that the polyurethane prepolymer is obtained by reacting polyether polyol PPG1000 and isocyanate. The preparation method is as follows: the polyether polyol is vacuum dehydrated at 110°C for 3 hours, then cooled to 50°C, and under nitrogen protection, isocyanate is added and heated to 90°C for 3 hours to obtain isocyanate-terminated polyurethane prepolymer 2 with a molar ratio of NCO to OH of 5:1.

[0086] Comparative Example 5

[0087] A detachable polyurethane thermally conductive structural adhesive and its preparation method are disclosed. The only difference from Example 1 is that the polyurethane prepolymer is obtained by reacting carbon dioxide copolymer polyol and isocyanate. The preparation method is as follows: polypropylene carbonate diol PCD-621 is dehydrated under vacuum at 110°C for 3 hours, then cooled to 50°C, and under nitrogen protection, isocyanate is added and heated to 90°C for 3 hours to obtain isocyanate-terminated polyurethane prepolymer 3 with a molar ratio of NCO to OH of 5:1.

[0088] Comparative Example 6

[0089] A detachable polyurethane thermally conductive structural adhesive and its preparation method are disclosed. The only difference from Example 1 is that the polyurethane prepolymer is obtained by reacting a small molecule carbon dioxide-based polyol with isocyanate. The preparation method is as follows: the small molecule carbon dioxide-based polyol is dehydrated under vacuum at 110°C for 3 hours, then cooled to 50°C, and under nitrogen protection, isocyanate is added and heated to 90°C for 3 hours to obtain isocyanate-terminated polyurethane prepolymer 4 with a molar ratio of NCO to OH of 5:1.

[0090] Table 2

[0091]

[0092] The performance of the polyurethane thermally conductive structural adhesives prepared in the examples and comparative examples was tested, and the test results are shown in Table 3.

[0093] Table 3

[0094]

[0095]

[0096] As shown in the table, the flame-retardant, detachable carbon dioxide-based polyurethane thermally conductive structural adhesive prepared in this invention maintains a hardness within the Shore D range of 60±5, a shear strength of 8.0 MPa or higher on an aluminum substrate, a tensile strength of 14.0 MPa or higher, flame retardancy reaching UL94 V0, and a shear strength of less than 0.5 MPa after 30 minutes at 90°C. Furthermore, its thermal conductivity reaches 1.2 W / m·K, demonstrating excellent overall performance. In contrast, the performance of the general-purpose polyether polyols used in Comparative Examples 1 and 2 is lower than that of the product in Example 1. Comparative Example 3 did not add expandable microspheres, and relying solely on structural modifiers could not achieve satisfactory detachability. Comparative Examples 4-6 used inappropriate types or ratios of polyols during the preparation of the polyurethane prepolymer, and the products prepared failed to achieve the comprehensive performance of the products in the examples.

[0097] The applicant declares that this invention illustrates the flame-retardant, detachable, carbon dioxide-based polyurethane thermally conductive structural adhesive, its preparation method, and its application through the above embodiments. However, this invention is not limited to the above embodiments, meaning that this invention does not necessarily rely on the above embodiments for implementation. Those skilled in the art should understand that any improvements to this invention, equivalent substitutions of raw materials, additions of auxiliary components, and selection of specific methods, etc., all fall within the protection and disclosure scope of this invention.

Claims

1. A flame-retardant, removable, carbon dioxide-based polyurethane thermally conductive structural adhesive, characterized in that, The polyurethane thermally conductive structural adhesive comprises component A and component B. Component A, by mass fraction, comprises the following raw materials: 15-40 parts of carbon dioxide copolymer polyol; 1-5 parts of structure modifier; 70-90 parts of the first thermally conductive filler; 1-5 parts of expandable microspheres; Component B comprises the following raw materials: 10-20 parts of polyurethane prepolymer; 5-15 parts isocyanate; 70-90 parts of the second thermally conductive filler; 1-5 parts of dehydrating agent; The polyurethane prepolymer is obtained by reacting carbon dioxide copolymer polyol, small molecule carbon dioxide-based polyol and isocyanate. The small molecule carbon dioxide-based polyol is a product obtained by reacting propylene carbonate with aliphatic polyamines.

2. The flame-retardant, detachable CO2-based polyurethane thermally conductive structural adhesive according to claim 1, characterized in that, The carbon dioxide copolymer polyol is a combination of one or at least two polypropylene carbonate polyols synthesized by copolymerizing carbon dioxide with propylene oxide under the action of an initiator and a catalyst.

3. The flame-retardant, detachable CO2-based polyurethane thermally conductive structural adhesive according to claim 1, characterized in that, The number-average molecular weight of the carbon dioxide copolymer polyol is 500~8000 g / mol.

4. The flame-retardant, detachable CO2-based polyurethane thermally conductive structural adhesive according to claim 1, characterized in that, The hydroxyl functionality of the carbon dioxide copolymer polyol is 2 to 5.

5. The flame-retardant, detachable CO2-based polyurethane thermally conductive structural adhesive according to claim 1, characterized in that, The molar fraction of intramolecular carbonate groups in the carbon dioxide copolymer polyol is 0.25~0.

45.

6. The flame-retardant, detachable CO2-based polyurethane thermally conductive structural adhesive according to claim 1, characterized in that, The structure modifier is a monohydric alcohol monomer with an electron-donating group containing a nitrogen atom.

7. The flame-retardant, detachable CO2-based polyurethane thermally conductive structural adhesive according to claim 1, characterized in that, The structure modifier is selected from one or a combination of at least two of N-hydroxyethyl-2-pyrrolidone, 2-hydroxyethylpyridine, N-hydroxyethylpyrrolidine, 3-hydroxymethylpyrrolidine, 2-hydroxymethylpyrrolidine, 1-methyl-3-pyrrolidone or N-hydroxyethylpiperidine.

8. The flame-retardant, detachable CO2-based polyurethane thermally conductive structural adhesive according to claim 1, characterized in that, The first thermally conductive filler is one or a combination of at least two of aluminum hydroxide, aluminum oxide, or boron nitride.

9. The flame-retardant, detachable, carbon dioxide-based polyurethane thermally conductive structural adhesive according to claim 1, characterized in that, The expandable microspheres are low-temperature expandable microspheres.

10. The flame-retardant, detachable, carbon dioxide-based polyurethane thermally conductive structural adhesive according to claim 1, characterized in that, The expandable microspheres are selected from Nouryon's 031 DU 40, 053 DU 40, 043 DU 80 or Matsumoto Oil & Fat Pharmaceutical Co., Ltd.'s F-48 or F-50, or a combination of at least two of these.

11. The flame-retardant, detachable CO2-based polyurethane thermally conductive structural adhesive according to claim 1, characterized in that, Component A also includes a coupling agent.

12. The flame-retardant, detachable CO2-based polyurethane thermally conductive structural adhesive according to claim 11, characterized in that, The coupling agent is selected from one or a combination of at least two of γ-glycidoxypropyltrimethoxysilane, γ-(2,3-epoxypropoxy)propyltrimethoxysilane, ureopropyltriethoxysilane, β-(3,4-epoxycyclohexyl)-ethyltrimethoxysilane, and γ-ureopropyltrimethoxysilane.

13. The flame-retardant, detachable CO2-based polyurethane thermally conductive structural adhesive according to claim 11, characterized in that, The coupling agent content in the raw materials of component A is 1 to 2 parts.

14. The flame-retardant, detachable, carbon dioxide-based polyurethane thermally conductive structural adhesive according to claim 1, characterized in that, Component A also includes a catalyst.

15. The flame-retardant, detachable CO2-based polyurethane thermally conductive structural adhesive according to claim 14, characterized in that, The catalyst is selected from one or a combination of at least two of organobismuth, organozinc, and dibutyltin dilaurate.

16. The flame-retardant, detachable CO2-based polyurethane thermally conductive structural adhesive according to claim 14, characterized in that, The catalyst content in the raw materials of component A is 0.02 to 0.1 parts.

17. The flame-retardant, detachable CO2-based polyurethane thermally conductive structural adhesive according to claim 1, characterized in that, The aliphatic polyamine is any one or a combination of at least two of the following: ethylenediamine, cyclohexanediamine, tris(2-aminoethyl)amine, tris(3-aminopropyl)amine, diethylenetriamine, triethylenetetramine, or tetraethylenepentamine.

18. The flame-retardant, detachable CO2-based polyurethane thermally conductive structural adhesive according to claim 1, characterized in that, The molecular weight of the small molecule carbon dioxide-based polyol is 200–700 g / mol.

19. The flame-retardant, detachable, carbon dioxide-based polyurethane thermally conductive structural adhesive according to claim 1, characterized in that, The functionality of the small molecule carbon dioxide-based polyol is 2 to 3.

20. The flame-retardant, detachable CO2-based polyurethane thermally conductive structural adhesive according to claim 1, characterized in that, The molar fraction of intramolecular carbonate groups in the small molecule carbon dioxide-based polyol is 0.25~0.

45.

21. The flame-retardant, detachable CO2-based polyurethane thermally conductive structural adhesive according to claim 1, characterized in that, In the raw materials for preparing the polyurethane prepolymer, the mass ratio of carbon dioxide copolymer polyol to small molecule carbon dioxide-based polyol is 100:(5~20).

22. The flame-retardant, detachable CO2-based polyurethane thermally conductive structural adhesive according to claim 1, characterized in that, The polyurethane prepolymer is prepared by mixing carbon dioxide copolymer polyol and small molecule carbon dioxide-based polyol evenly, removing water, and then adding isocyanate to react and obtain the polyurethane prepolymer.

23. The flame-retardant, detachable CO2-based polyurethane thermally conductive structural adhesive according to claim 22, characterized in that, The water removal process involves vacuum dehydration at 100-120°C for 2-3 hours.

24. The flame-retardant, detachable CO2-based polyurethane thermally conductive structural adhesive according to claim 22, characterized in that, After dehydration, the temperature is lowered to 40-60°C, and isocyanate is added under nitrogen protection to carry out the reaction.

25. The flame-retardant, detachable, carbon dioxide-based polyurethane thermally conductive structural adhesive according to claim 22, characterized in that, The reaction temperature for adding isocyanate is 80~90℃, and the reaction time is 2~3h.

26. The flame-retardant, detachable, carbon dioxide-based polyurethane thermally conductive structural adhesive according to claim 1, characterized in that, The isocyanate is one or a combination of at least two of diphenylmethane diisocyanate and polyphenylmethylene polyisocyanate.

27. The flame-retardant, detachable, carbon dioxide-based polyurethane thermally conductive structural adhesive according to claim 1, characterized in that, The second thermally conductive filler is one or a combination of at least two of aluminum hydroxide, aluminum oxide, or boron nitride.

28. The flame-retardant, detachable CO2-based polyurethane thermally conductive structural adhesive according to claim 1, characterized in that, The dehydrating agent is one or a combination of at least two of molecular sieve activated powder and p-toluenesulfonyl isocyanate.

29. The flame-retardant, detachable, carbon dioxide-based polyurethane thermally conductive structural adhesive according to claim 1, characterized in that, The volume ratio of component A to component B is 1:0.8 to 1.

2.

30. A method for preparing a flame-retardant, removable carbon dioxide-based polyurethane thermally conductive structural adhesive according to any one of claims 1-29, the method comprising the following steps: (1) Add carbon dioxide copolymer polyol and first thermally conductive filler into the reactor, remove water, cool down, then add expandable microspheres, structure regulator, optional coupling agent, optional catalyst and mix evenly under vacuum to obtain component A; (2) The polyurethane prepolymer, isocyanate, second thermally conductive filler and dehydrating agent are added into the reactor and mixed and degassed under vacuum to obtain component B.

31. The preparation method according to claim 30, characterized in that, The water removal in step (1) is performed by vacuum dehydration at 110~120℃ for 2~3 hours.

32. The preparation method according to claim 30, characterized in that, The cooling refers to reducing the temperature to 40~60℃.

33. The preparation method according to claim 30, characterized in that, The expandable microspheres in step (1) are expandable microspheres that have been freeze-dried.

34. The application of the flame-retardant, removable carbon dioxide-based polyurethane thermally conductive structural adhesive according to any one of claims 1-29 in the bonding of thermally conductive structures in new energy batteries.

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