Polyurethane viscosity-reducing adhesive for power battery and preparation method of polyurethane viscosity-reducing adhesive

Abstract

The invention belongs to the technical field of preparation of polyurethane functional materials, and particularly relates to a polyurethane viscosity-reducing adhesive for a power battery and a preparation method of the polyurethane viscosity-reducing adhesive. According to the present invention, the polyurethane viscosity-reducing glue for the power battery is synthesized through the reaction of the bifunctional isocyanate and the polyol, and the fluorine-modified balloon-coated cross-linking agent is introduced into the system so as to release the cross-linking agent under the alternate cooling and heating condition, such that the post-crosslinking is performed, and the volume of the adhesive is shrunk so as to achieve the viscosity-reducing purpose; the device is mainly suitable for rapidly detaching the PACK glue of the power battery, and the detaching process is simple, rapid and efficient.

Description

Technical Field

[0001] The invention belongs to the technical field of preparation of polyurethane functional materials, and specifically relates to a polyurethane viscosity-reducing adhesive for power batteries and a preparation method thereof. Background Art

[0002] Polyurethane refers to a synthetic polymer with carbamate repeating units in the polymer main chain. It is one of the most commonly used materials for preparing adhesives and has excellent acid resistance and low temperature resistance. With the rapid development of the electric vehicle industry, power batteries have also ushered in a blowout development. Whether it is when the power battery fails and needs to be disassembled for repair, or when the battery expires in the future and needs to be recycled and disassembled, the battery PACK packaging needs to be removed. During battery production, the battery PACK glue is poured between the battery module and the PACK in the form of potting in order to prevent moisture, shock, and impact, which brings great difficulties to disassembly. Therefore, there is an urgent need for a PACK glue that is simple, fast, and convenient to disassemble.

[0003] Although traditional PACK glue can achieve a firm connection between power battery packs, when the battery encounters problems or needs to be recycled, due to the characteristics of high-strength structural bonding, a series of disassembly difficulties arise in the recycling process. For example, there is a large amount of high-strength adhesive between the battery cell and the cover plate, which cannot be opened directly; there is a large amount of high-elastic adhesive between the side of the battery cell and the battery pack rib plate, the battery cell is tightly bonded, and physical disassembly is difficult; there is also high-strength structural adhesive at the four corners where the top battery cell contacts the battery pack shell. The current main disassembly methods are to use adhesive dissolving agents or physical disassembly, but the former will use a large amount of solvents, which will not only cause waste of resources but also cause environmental pollution. Although the latter is relatively safe, highly controllable, and less polluting, it is accompanied by problems such as incomplete adhesive removal, the need for equipment assistance, and long unit time. Summary of the invention

[0004] The present invention proposes a polyurethane viscosity-reducing adhesive and a preparation method thereof. The polyurethane is cross-linked by designing the adhesive into an incompletely cross-linked structure. After being subjected to a cold and hot shock of -30 to 60°C within 70 seconds, the cross-linking agent released by the fluorine balloon cross-links the polyurethane. After 10 cycles, the adhesive shrinks in volume due to rapid curing, and wrinkles and bubbles are generated at the interface between the adhesive and the battery PACK packaging, thereby reducing the viscosity and achieving the purpose of viscosity reduction. The problem of difficult disassembly of the battery PACK can be solved.

[0005] The polyurethane viscosity-reducing adhesive of the present invention overcomes the disadvantage of high adhesive residue during disassembly by traditional physical disassembly methods, and compared with debonding agents, no solvent is required, thereby reducing environmental pollution. At the same time, due to its advantages of high efficiency and low cost, it can greatly reduce the difficulty of disassembling battery PACKs, greatly reduce the cost of maintenance and recycling, and has extremely high application value.

[0006] The polyurethane adhesive of the present invention is prepared by gradually polymerizing a bifunctional polyol, an isocyanate and a small molecule chain extender, and then adding the isocyanate wrapped in a fluorine balloon. The structural formula is as follows (wherein -NHCOO- can be replaced by -NHCONH-):

[0007] HO-R2-OOCNH-R1-NHCOO-R2-OOCNH-R1-NHCOO-R2-OOCNH-R1-NHCOO-R 2 -OH

[0008]

[0009] The specific preparation method of polyurethane viscosity-reducing adhesive is as follows:

[0010] (1) adding isocyanate and an organic tin catalyst to a difunctional polyol that has been subjected to vacuum dehydration treatment, dissolving the mixture in an organic solvent, and stirring the mixture at 75-85° C. for 2 h to obtain a viscous and transparent polyurethane prepolymer FPU-1;

[0011] Wherein, the difunctional polyol is one of polytetramethylene glycol, polyethylene adipate, polybutylene adipate, polyhexylene adipate or polycaprolactone diol, Mn=500-5000. The isocyanate is one of isophorone diisocyanate, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, diphenylmethane diisocyanate, dicyclohexylmethane diisocyanate and hexamethylene diisocyanate.

[0012] The molar ratio of isocyanate to difunctional polyol is 2:1

[0013] (2) dissolving the fluorinated polyol in an organic solvent and adding the solution to the FPU-1 in step (1), reacting at 75-85° C. for 1 h to obtain a viscous isocyanate-terminated fluorinated polyurethane FPU-2;

[0014] Wherein, the fluorine-containing polyol is tetrafluorobutanediol, hexafluoropentanediol or octafluorohexanediol; and the molar ratio of the fluorine-containing polyol to the difunctional polyol is 1:1.

[0015] (3) FPU-2 is placed as a wall material in the gap between the inner and outer walls of a concentric metal tube, and is blown into the tube by gas. Isocyanate, as a core material, naturally falls from the inside and forms droplets after being wrapped. After solidification, it forms a crosslinking agent coated with a fluorine-modified balloon;

[0016] The isocyanate is one of isophorone diisocyanate, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, diphenylmethane diisocyanate, dicyclohexylmethane diisocyanate and hexamethylene diisocyanate.

[0017] The mass ratio of wall material to core material is 3:1.

[0018] (4) adding isocyanate and an organic tin catalyst to the difunctional polyol treated by vacuum dehydration, dissolving the mixture with an organic solvent, and stirring the mixture at 75-85° C. for 2 h to obtain a viscous and transparent polyurethane prepolymer PU-1;

[0019] The difunctional polyol is one of polytetramethylene glycol, polyethylene adipate, polybutylene adipate, polyhexylene adipate or polycaprolactone diol, with Mn=500-5000; the isocyanate is one of isophorone diisocyanate, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, diphenylmethane diisocyanate, dicyclohexylmethane diisocyanate and hexamethylene diisocyanate; and the molar ratio of the isocyanate to the difunctional polyol is 2:1.

[0020] (5) dissolving a small molecule diol chain extender in an organic solvent and adding the resultant to PU-1, and performing a chain extension reaction at 55-65° C. for 1 h to obtain a viscous hydroxyl-terminated polyurethane PU-2;

[0021] The small molecule diol chain extender can be one of 1,4-butanediol, propylene glycol, 1,6-hexanediol, ethylene glycol, and neopentyl glycol, and the molar ratio of the small molecule diol chain extender to the difunctional polyol is 3:1.

[0022] (6) Adding a fluorine-modified balloon-coated crosslinking agent dissolved in an organic solvent to PU-2, stirring the system at 35-45° C. for 30 min to uniformly disperse it, thereby obtaining a viscous polyurethane adhesive containing a fluorine-modified balloon-coated crosslinking agent.

[0023] Among them, the mass ratio of PU-2 to the cross-linking agent coated with the fluorine-modified balloon is 2:1.

[0024] The organic solvent used in the above steps (1)-(2), (4)-(6) is one of: N,N-dimethylformamide, acetone, ethyl acetate, butyl acetate, toluene, xylene, dichloromethane, and tetrahydrofuran.

[0025] The organic tin catalyst used in the above steps (1) and (4) is: dibutyltin dilaurate or stannous octoate, and the amount of the organic tin catalyst is 0.25-0.5wt% of the mass of the difunctional polyol.

[0026] Beneficial effects:

[0027] The present invention prepares an incompletely cross-linked polyurethane material and adds a cross-linking agent wrapped in a fluorine balloon, so that the viscosity-reducing adhesive can be further cross-linked and cured under hot and cold shocks, so that wrinkles and bubbles are generated between it and the battery PACK, making it easy to disassemble. This method not only greatly reduces the recycling cost of power batteries, but also has the advantages of low pollution, short unit time, and thorough glue removal. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is the infrared spectrum of the viscosity-reducing adhesive prepared in Example 1 after curing.

[0029] Figure 2 The diagram is a schematic diagram of the preparation method of the fluorine-containing balloon in Example 1. DETAILED DESCRIPTION

[0030] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other implementation methods obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0031] Example 1

[0032] 20 g of polytetrahydrofuran diol (Mn=1000) dissolved in 30 ml of N,N-dimethylformamide and dehydrated in a vacuum at 100° C. for 2 hours was added to a 100 ml three-necked flask dried in a blast oven and treated with nitrogen, 8.88 g of isophorone diisocyanate and 0.03 g of an organotin catalyst were added, and the mixture was reacted at 80° C. for 2 hours to obtain a viscous isocyanate-terminated polyurethane prepolymer FPU-1. ; Add 3.24g of tetrafluorobutanediol dissolved in 2.5mlN,N-dimethylformamide, react at 80℃ for 1h to obtain viscous isocyanate-terminated fluorinated polyurethane FPU-2. Then, place FPU-2 as a wall material in the gap between the inner and outer walls of the concentric metal tubes, blow gas into and let it fall, and isocyanate as a core material naturally falls from the inside, is wrapped to form droplets, and after curing, forms a fluorine-modified balloon-coated crosslinker FPU.

[0033] 20 g of polytetrahydrofuran diol (Mn=2000) dissolved in 30 ml of N, N-dimethylformamide and subjected to vacuum dehydration treatment at 100° C. for 2 hours was added to a 100 ml three-necked flask dried in a blast oven and treated with nitrogen, and 4.44 g of isophorone diisocyanate was added, and the mixture was reacted at 80° C. for 2 hours to obtain a viscous isocyanate-terminated polyurethane prepolymer PU-1; 2.7 g of 1,4-butanediol dissolved in 2.5 ml of N, N-dimethylformamide was added, and the mixture was reacted at 60° C. for 1 hour to obtain a viscous transparent polyurethane PU-2; 13.57 g of a fluorine-modified balloon dissolved in 5 ml of N, N-dimethylformamide was added, and the system was stirred at 40° C. for 30 minutes to uniformly disperse it, to obtain a viscous fluorine-modified balloon-coated crosslinker polyurethane viscosity-reducing adhesive.

[0034] Infrared analysis showed that the product -1 The characteristic peak of the isocyanate group disappears, indicating that the prepolymer reaction is complete; 1440cm -1 and 2910cm -1 Left and right are -CH 2 The characteristic peak of 1700cm -1 is the characteristic peak of carbonyl, 3300cm -1 The left and right are characteristic peaks of hydroxyl groups. The above results prove that the polyurethane viscosity-reducing adhesive is successfully synthesized and the terminal group is hydroxyl group.

[0035] In order to verify that the viscosity-reducing adhesive has bonding strength, the shear strength of the viscosity-reducing adhesive was tested using a WDT-3030KN tensile testing machine. Two 100mm×25mm×1.6mm metal strips were bonded using the adhesive. The bonding surface length was 12.5mm. The shear strength was measured three times in parallel and was 3.21MPa.

[0036] In order to verify the disassembly performance of the viscosity-reducing adhesive, the bonded samples were subjected to a hot and cold shock of -30 to 60°C within 70 seconds, and the shear strength test was performed again. The test result was 0.16 MPa.

[0037] Example 2

[0038] 20 g of polyethylene adipate (Mn=2000) which had been subjected to vacuum dehydration treatment at 100° C. for 2 hours and dissolved in 30 ml of N,N-dimethylformamide was added to a 100 ml three-necked flask which had been dried in a blast oven and treated with nitrogen, 4.44 g of isophorone diisocyanate and 0.03 g of an organic tin catalyst were added, and the mixture was reacted at 80° C. for 2 hours to obtain a viscous isocyanate-terminated polyurethane prepolymer FPU-1; 2.12 g of hexafluoropentanediol dissolved in 2.5 ml of N,N-dimethylformamide was added, and the mixture was reacted at 80° C. for 1 hour to obtain a viscous isocyanate-terminated fluorinated polyurethane FPU-2, and then a viscous fluorinated balloon FPU was obtained (the preparation method was the same as in Example 1).

[0039] Take 20g of polytetrahydrofuran diol (Mn=2000) dissolved in 30mlN,N-dimethylformamide and dehydrated in vacuum at 100°C for 2 hours, add it to a 100ml three-necked flask dried in a blast oven and treated with nitrogen, add 4.44g of isophorone diisocyanate, react at 80°C for 2h, and obtain a viscous isocyanate-terminated polyurethane prepolymer PU-1; add 2.7g of 1,4-butanediol dissolved in 2.5ml of N,N-dimethylformamide, react at 60°C for 1h, and obtain a viscous transparent polyurethane PU-2; then add 13.57g of fluorine-modified balloon dissolved in 5ml of N,N-dimethylformamide, stir the system at 40°C for 30min to make it evenly dispersed, and obtain a viscous fluorine-modified balloon coated with a crosslinker polyurethane viscosity-reducing adhesive.

[0040] The shear strength of the viscosity-reducing adhesive was measured to be 2.95 MPa, and the shear strength after hot and cold shock was 0.22 MPa.

[0041] Example 3

[0042] 20 g of polytetrahydrofuran diol (Mn=2000) dissolved in 30 ml of N,N-dimethylformamide and subjected to vacuum dehydration treatment at 100° C. for 2 hours was added to a 100 ml three-necked flask dried in a blast oven and treated with nitrogen, 4.44 g of isophorone diisocyanate and 0.03 g of an organic tin catalyst were added, and the mixture was reacted at 80° C. for 2 hours to obtain a viscous isocyanate-terminated polyurethane prepolymer FPU-1; 1.62 g of tetrafluorobutanediol dissolved in 2.5 ml of N,N-dimethylformamide was added, and the mixture was reacted at 80° C. for 1 hour to obtain a viscous isocyanate-terminated fluorinated polyurethane FPU-2, and then a viscous fluorinated balloon FPU was obtained (the preparation method is the same as that in Example 1).

[0043] Take 20g of polyethylene adipate (Mn=1000) dissolved in 30mlN,N-dimethylformamide and dehydrated in vacuum at 100°C for 2 hours, add it to a 100ml three-necked flask dried in a blast oven and treated with nitrogen, add 6.96g of 2,6-toluene diisocyanate, react at 80°C for 2h, and obtain a viscous isocyanate-terminated polyurethane prepolymer PU-1; add 5.4g of 1,4-butanediol dissolved in 2.5ml of N,N-dimethylformamide, react at 60°C for 1h, and obtain a viscous transparent polyurethane PU-2; then add 16.18g of fluorine-modified balloon dissolved in 5ml of N,N-dimethylformamide, stir the system at 40°C for 30min to make it evenly dispersed, and obtain a viscous fluorine-modified balloon coated with a crosslinker polyurethane viscosity-reducing adhesive.

[0044] The shear strength of the viscosity-reducing adhesive was measured to be 3.15 MPa, and the shear strength after hot and cold shock was 0.16 MPa.

[0045] Example 4

[0046] 20 g of polyethylene adipate (Mn=1000) which had been subjected to vacuum dehydration treatment at 100° C. for 2 hours and dissolved in 30 ml of N,N-dimethylformamide was added to a 100 ml three-necked flask which had been dried in a blast oven and treated with nitrogen, 8.88 g of isophorone diisocyanate and 0.03 g of an organic tin catalyst were added, and the mixture was reacted at 80° C. for 2 hours to obtain a viscous isocyanate-terminated polyurethane prepolymer FPU-1; 3.24 g of tetrafluorobutanediol dissolved in 2.5 ml of N,N-dimethylformamide was added, and the mixture was reacted at 80° C. for 1 hour to obtain a viscous isocyanate-terminated fluorinated polyurethane FPU-2, and then a viscous fluorinated balloon FPU was obtained (the preparation method was the same as in Example 1).

[0047] Take 20g of polyethylene adipate (Mn=2000) dissolved in 30mlN,N-dimethylformamide and dehydrated in vacuum at 100°C for 2 hours, add it to a 100ml three-necked flask dried in a blast oven and treated with nitrogen, add 3.48g of 2,4-toluene diisocyanate, react at 80°C for 2h, and obtain a viscous isocyanate-terminated polyurethane prepolymer PU-1; add 2.7g of 1,4-butanediol dissolved in 2.5ml of N,N-dimethylformamide, react at 60°C for 1h, and obtain a viscous transparent polyurethane PU-2; then add 13.09g of fluorine-modified balloon dissolved in 5ml of N,N-dimethylformamide, stir the system at 40°C for 30min to make it evenly dispersed, and obtain a viscous fluorine-modified balloon coated with a crosslinker polyurethane viscosity-reducing adhesive.

[0048] The shear strength of the viscosity-reducing adhesive was measured to be 3.42 MPa, and the shear strength after hot and cold shock was 0.19 MPa.

[0049] Example 5

[0050] 20 g of polybutylene adipate (Mn=1000) dissolved in 30 ml of N,N-dimethylformamide and subjected to vacuum dehydration treatment at 100° C. for 2 hours was added to a 100 ml three-necked flask dried in a blast oven and treated with nitrogen, 6.96 g of 2,4-toluene diisocyanate and 0.03 g of an organic tin catalyst were added, and the mixture was reacted at 80° C. for 2 hours to obtain a viscous isocyanate-terminated polyurethane prepolymer FPU-1; 3.24 g of tetrafluorobutanediol dissolved in 2.5 ml of N,N-dimethylformamide was added, and the mixture was reacted at 80° C. for 1 hour to obtain a viscous isocyanate-terminated fluorinated polyurethane FPU-2, and then a viscous fluorinated balloon FPU was obtained (the preparation method is the same as that in Example 1).

[0051] 20 g of polybutylene adipate (Mn=1000) dissolved in 30 ml N, N-dimethylformamide and subjected to vacuum dehydration treatment at 100°C for 2 hours was added to a 100 ml three-necked flask dried in a blast oven and treated with nitrogen, and 6.96 g of 2,4-toluene diisocyanate was added, and the mixture was reacted at 80°C for 2 hours to obtain a viscous isocyanate-terminated polyurethane prepolymer PU-1; 5.4 g of 1,4-butanediol dissolved in 2.5 ml N, N-dimethylformamide was added, and the mixture was reacted at 60°C for 1 hour to obtain a viscous transparent polyurethane PU-2; 16.18 g of a fluorine-modified balloon dissolved in 5 ml N, N-dimethylformamide was added, and the system was stirred at 40°C for 30 minutes to uniformly disperse the balloon, to obtain a viscous fluorine-modified balloon-coated crosslinker polyurethane viscosity-reducing adhesive.

[0052] The shear strength of the viscosity-reducing adhesive was measured to be 3.34 MPa, and the shear strength after hot and cold shock was 0.28 MPa.

[0053] Example 6

[0054] 20 g of polybutylene adipate (Mn=2000) dissolved in 30 ml of N,N-dimethylformamide and subjected to vacuum dehydration treatment at 100° C. for 2 hours was added to a 100 ml three-necked flask dried in a blast oven and treated with nitrogen, 3.48 g of 2,6-toluene diisocyanate and 0.03 g of an organic tin catalyst were added, and the mixture was reacted at 80° C. for 2 hours to obtain a viscous isocyanate-terminated polyurethane prepolymer FPU-1; 2.12 g of hexafluoropentanediol dissolved in 2.5 ml of N,N-dimethylformamide was added, and the mixture was reacted at 80° C. for 1 hour to obtain a viscous isocyanate-terminated fluorinated polyurethane FPU-2, and then a viscous fluorinated balloon FPU was obtained (the preparation method is the same as that in Example 1).

[0055] 20 g of polybutylene adipate (Mn=2000) dissolved in 30 ml N, N-dimethylformamide and subjected to vacuum dehydration treatment at 100 ° C for 2 hours was added to a 100 ml three-necked flask dried in a blast oven and treated with nitrogen, and 3.48 g of 2,6-toluene diisocyanate was added, and the reaction was carried out at 80 ° C for 2 hours to obtain a viscous isocyanate-terminated polyurethane prepolymer PU-1; 2.7 g of 1,4-butanediol dissolved in 2.5 ml N, N-dimethylformamide was added, and the reaction was carried out at 60 ° C for 1 hour to obtain a viscous transparent polyurethane PU-2; 13.09 g of fluorine-modified balloon dissolved in 5 ml N, N-dimethylformamide was added, and the system was stirred at 40 ° C for 30 minutes to make it uniformly dispersed, and a viscous fluorine-modified balloon coated with a crosslinker polyurethane viscosity-reducing adhesive was obtained.

[0056] The shear strength of the viscosity-reducing adhesive was measured to be 3.14 MPa, and the shear strength after hot and cold shock was 0.16 MPa.

[0057] Example 7

[0058] 20 g of poly(hexamethylene adipate) (Mn=1000) which had been subjected to vacuum dehydration treatment at 100° C. for 2 hours and dissolved in 30 ml of N,N-dimethylformamide was added to a 100 ml three-necked flask which had been dried in a blast oven and treated with nitrogen, 10 g of diphenylmethane diisocyanate and 0.03 g of an organic tin catalyst were added, and the mixture was reacted at 80° C. for 2 hours to obtain a viscous isocyanate-terminated polyurethane prepolymer FPU-1; 3.24 g of tetrafluorobutanediol dissolved in 2.5 ml of N,N-dimethylformamide was added, and the mixture was reacted at 80° C. for 1 hour to obtain a viscous isocyanate-terminated fluorinated polyurethane FPU-2, and then a viscous fluorinated balloon FPU was obtained (the preparation method was the same as in Example 1).

[0059] Take 20g of poly(hexanediol adipate) (Mn=1000) dissolved in 30mlN,N-dimethylformamide and subjected to vacuum dehydration treatment at 100°C for 2 hours, add it into a 100ml three-necked flask dried in a blast oven and treated with nitrogen, add 10g of diphenylmethane diisocyanate, react at 80°C for 2h, and obtain a viscous isocyanate-terminated polyurethane prepolymer PU-1; add 3.72g of ethylene glycol dissolved in 2.5ml of N,N-dimethylformamide, react at 60°C for 1h, and obtain a viscous transparent polyurethane PU-2; then add 16.86g of a fluorine-modified balloon dissolved in 5ml of N,N-dimethylformamide, stir the system at 40°C for 30min to make it evenly dispersed, and obtain a viscous fluorine-modified balloon-coated crosslinker polyurethane viscosity-reducing adhesive.

[0060] The shear strength of the viscosity-reducing adhesive was measured to be 3.75 MPa, and the shear strength after hot and cold shock was 0.11 MPa.

[0061] Example 8

[0062] 20 g of poly(hexylene adipate) (Mn=2000) which had been subjected to vacuum dehydration treatment at 100° C. for 2 hours and dissolved in 30 ml of N,N-dimethylformamide was added to a 100 ml three-necked flask which had been dried in a blast oven and treated with nitrogen, 5 g of diphenylmethane diisocyanate and 0.03 g of an organic tin catalyst were added, and the mixture was reacted at 80° C. for 2 hours to obtain a viscous isocyanate-terminated polyurethane prepolymer FPU-1; 1.62 g of tetrafluorobutanediol dissolved in 2.5 ml of N,N-dimethylformamide was added, and the mixture was reacted at 80° C. for 1 hour to obtain a viscous isocyanate-terminated fluorinated polyurethane FPU-2, and then a viscous fluorinated polyurethane FPU-1 was obtained (the preparation method was the same as in Example 1).

[0063] Take 20g of poly(hexanediol adipate) (Mn=2000) dissolved in 30mlN,N-dimethylformamide and subjected to vacuum dehydration treatment at 100°C for 2 hours, add it to a 100ml three-necked flask dried in a blast oven and treated with nitrogen, add 5g of diphenylmethane diisocyanate, react at 80°C for 2h to obtain a viscous isocyanate-terminated polyurethane prepolymer PU-1; add 1.86g of ethylene glycol dissolved in 2.5ml of N,N-dimethylformamide, react at 60°C for 1h to obtain a viscous transparent polyurethane PU-2; then add 13.43g of a fluorine-modified balloon dissolved in 5ml of N,N-dimethylformamide, stir the system at 40°C for 30min to make it evenly dispersed, and obtain a viscous fluorine-modified balloon-coated crosslinker polyurethane viscosity-reducing adhesive.

[0064] The shear strength of the viscosity-reducing adhesive was measured to be 3.96 MPa, and the shear strength after hot and cold shock was 0.35 MPa.

[0065] Example 9

[0066] Take 20g of polycaprolactone diol (Mn=1000) dissolved in 30mlN,N-dimethylformamide and subjected to vacuum dehydration treatment at 100°C for 2 hours, add it into a 100ml three-necked flask dried in a blast oven and treated with nitrogen, add 6.72g of hexamethylene diisocyanate and 0.03g of an organic tin catalyst, and react at 80°C for 2h to obtain a viscous isocyanate-terminated polyurethane prepolymer FPU-1; add 3.24g of tetrafluorobutanediol dissolved in 2.5mlN,N-dimethylformamide, and react at 80°C for 1h to obtain a viscous isocyanate-terminated fluorine-containing polyurethane FPU-2, and then, obtain a viscous fluorine-containing balloon FPU (preparation method is the same as Example 1).

[0067] Take 20g of polycaprolactone diol (Mn=1000) dissolved in 30mlN,N-dimethylformamide and subjected to vacuum dehydration treatment at 100°C for 2 hours, add it into a 100ml three-necked flask dried in a blast oven and treated with nitrogen, add 6.72g of hexamethylene diisocyanate, react at 80°C for 2h, and obtain a viscous isocyanate-terminated polyurethane prepolymer PU-1; add 6.24g of neopentyl glycol dissolved in 2.5ml of N,N-dimethylformamide, react at 60°C for 1h, and obtain a viscous transparent polyurethane PU-2; then add 16.48g of fluorine-modified balloon dissolved in 5ml of N,N-dimethylformamide, stir the system at 40°C for 30min to make it evenly dispersed, and obtain a viscous fluorine-modified balloon coated with a crosslinker polyurethane viscosity-reducing adhesive.

[0068] The shear strength of the viscosity-reducing adhesive was measured to be 3.67 MPa, and the shear strength after hot and cold shock was 0.37 MPa.

[0069] Example 10

[0070] 20 g of polytetrahydrofuran diol (Mn=1000) which had been subjected to vacuum dehydration treatment at 100° C. for 2 hours and dissolved in 30 ml of N,N-dimethylformamide was added into a 100 ml three-necked flask which had been dried in a blast oven and treated with nitrogen, 6.72 g of hexamethylene diisocyanate and 0.03 g of an organic tin catalyst were added, and the mixture was reacted at 80° C. for 2 hours to obtain a viscous isocyanate-terminated polyurethane prepolymer FPU-1; 5.24 g of octafluorohexanediol dissolved in 2.5 ml of N,N-dimethylformamide was added, and the mixture was reacted at 80° C. for 1 hour to obtain a viscous isocyanate-terminated fluorinated polyurethane FPU-2, and then a viscous fluorinated balloon FPU was obtained (the preparation method was the same as in Example 1).

[0071] Take 20g of polycaprolactone diol (Mn=1000) dissolved in 30mlN,N-dimethylformamide and dehydrated in vacuum at 100°C for 2 hours, add it to a 100ml three-necked flask dried in a blast oven and treated with nitrogen, add 6.72g of hexamethylene diisocyanate, react at 80°C for 2h, and obtain a viscous isocyanate-terminated polyurethane prepolymer PU-1; add 7.08g of 1,6-hexanediol dissolved in 2.5ml of N,N-dimethylformamide, react at 60°C for 1h, and obtain a viscous transparent polyurethane PU-2; then add 16.90g of fluorine-modified balloon dissolved in 5ml of N,N-dimethylformamide, stir the system at 40°C for 30min to make it evenly dispersed, and obtain a viscous fluorine-modified balloon coated with a crosslinker polyurethane viscosity-reducing adhesive.

[0072] The shear strength of the viscosity-reducing adhesive was measured to be 3.26 MPa, and the shear strength after hot and cold shock was 0.18 MPa.

[0073] Embodiment 11

[0074] 20 g of polybutylene adipate (Mn=1000) which had been subjected to vacuum dehydration treatment at 100° C. for 2 hours and dissolved in 30 ml of N,N-dimethylformamide was added to a 100 ml three-necked flask which had been dried in a blast oven and treated with nitrogen, 6.96 g of 2,6-toluene diisocyanate and 0.03 g of an organic tin catalyst were added, and the mixture was reacted at 80° C. for 2 hours to obtain a viscous isocyanate-terminated polyurethane prepolymer FPU-1; 5.24 g of octafluorohexanediol dissolved in 2.5 ml of N,N-dimethylformamide was added, and the mixture was reacted at 80° C. for 1 hour to obtain a viscous isocyanate-terminated fluorinated polyurethane FPU-2, and then a viscous fluorinated balloon FPU was obtained (the preparation method was the same as in Example 1).

[0075] Take 20g of polycaprolactone diol (Mn=2000) dissolved in 30mlN,N-dimethylformamide and dehydrated in vacuum at 100°C for 2 hours, add it to a 100ml three-necked flask dried in a blast oven and treated with nitrogen, add 3.36g of hexamethylene diisocyanate, react at 80°C for 2h, and obtain a viscous isocyanate-terminated polyurethane prepolymer PU-1; add 2.28g of propylene glycol dissolved in 2.5ml of N,N-dimethylformamide, react at 60°C for 1h, and obtain a viscous transparent polyurethane PU-2; then add 12.82g of fluorine-modified balloon dissolved in 5ml of N,N-dimethylformamide, stir the system at 40°C for 30min to make it evenly dispersed, and obtain a viscous fluorine-modified balloon coated with a crosslinker polyurethane viscosity-reducing adhesive.

[0076] The shear strength of the viscosity-reducing adhesive was measured to be 3.27 MPa, and the shear strength after hot and cold shock was 0.19 MPa.

[0077] Example 12

[0078] 20 g of polybutylene adipate (Mn=2000) dissolved in 30 ml of N,N-dimethylformamide and subjected to vacuum dehydration treatment at 100° C. for 2 hours was added to a 100 ml three-necked flask dried in a blast oven and treated with nitrogen, 3.48 g of 2,4-toluene diisocyanate and 0.03 g of an organic tin catalyst were added, and the mixture was reacted at 80° C. for 2 hours to obtain a viscous isocyanate-terminated polyurethane prepolymer FPU-1; 1.62 g of tetrafluorobutanediol dissolved in 2.5 ml of N,N-dimethylformamide was added, and the mixture was reacted at 80° C. for 1 hour to obtain a viscous isocyanate-terminated fluorinated polyurethane FPU-2, and then a viscous fluorinated balloon FPU was obtained (the preparation method is the same as that in Example 1).

[0079] 20 g of polytetrahydrofuran diol (Mn = 1000) dissolved in 30 ml of N,N-dimethylformamide, which had been dehydrated by vacuum pumping at 100 °C for 2 hours, was added to a 100 ml three-necked flask that had been dried in a forced-air oven and treated with nitrogen. 6.72 g of hexamethylene diisocyanate was added, and the reaction was carried out at 80 °C for 2 h to obtain a viscous isocyanate-terminated polyurethane prepolymer PU-1; 4.56 g of propylene glycol dissolved in 2.5 ml of N,N-dimethylformamide was added, and the reaction was carried out at 60 °C for 1 h to obtain a viscous transparent polyurethane PU-2; then 15.64 g of fluorine-modified balloons dissolved in 5 ml of N,N-dimethylformamide was added, and the system was stirred at 40 °C for 30 min to disperse it evenly, obtaining a viscous polyurethane tackifier containing fluorine-modified balloon-coated crosslinking agent.

[0080] The shear strength of the tackifier was measured to be 4.11 MPa. The shear strength after thermal cycling was 0.19 MPa.

[0081] Example 13

[0082] 20 g of polytetrahydrofuran diol (Mn = 1000) dissolved in 30 ml of N,N-dimethylformamide, which had been dehydrated by vacuum pumping at 100 °C for 2 hours, was added to a 100 ml three-necked flask that had been dried in a forced-air oven and treated with nitrogen. 10 g of diphenylmethane diisocyanate and 0.03 g of organotin catalyst were added, and the reaction was carried out at 80 °C for 2 h to obtain a viscous isocyanate-terminated polyurethane prepolymer FPU-1; 4.24 g of hexafluoropentanediol dissolved in 2.5 ml of N,N-dimethylformamide was added, and the reaction was carried out at 80 °C for 1 h to obtain a viscous isocyanate-terminated fluorinated polyurethane FPU-2, and then a viscous fluorinated balloon FPU was obtained (the preparation method was the same as in Example 1).

[0083] 20 g of polytetrahydrofuran diol (Mn = 1000) dissolved in 30 ml of N,N-dimethylformamide, which had been dehydrated by vacuum pumping at 100 °C for 2 hours, was added to a 100 ml three-necked flask that had been dried in a forced-air oven and treated with nitrogen. 10 g of diphenylmethane diisocyanate was added, and the reaction was carried out at 80 °C for 2 h to obtain a viscous isocyanate-terminated polyurethane prepolymer PU-1; 4.56 g of propylene glycol dissolved in 2.5 ml of N,N-dimethylformamide was added, and the reaction was carried out at 60 °C for 1 h to obtain a viscous transparent polyurethane PU-2; then 17.28 g of fluorine-modified balloons dissolved in 5 ml of N,N-dimethylformamide was added, and the system was stirred at 40 °C for 30 min to disperse it evenly, obtaining a viscous polyurethane tackifier containing fluorine-modified balloon-coated crosslinking agent.

[0084] The shear strength of the tackifier was measured to be 3.21 MPa. The shear strength after thermal cycling was 0.18 MPa.

[0085] Embodiment 14

[0086] 20 g of polybutylene adipate (Mn=2000) which had been subjected to vacuum dehydration treatment at 100° C. for 2 hours and dissolved in 30 ml of N,N-dimethylformamide was added to a 100 ml three-necked flask which had been dried in a blast oven and treated with nitrogen, 5 g of diphenylmethane diisocyanate and 0.03 g of an organic tin catalyst were added, and the mixture was reacted at 80° C. for 2 hours to obtain a viscous isocyanate-terminated polyurethane prepolymer FPU-1; 2.62 g of octafluorohexanediol dissolved in 2.5 ml of N,N-dimethylformamide was added, and the mixture was reacted at 80° C. for 1 hour to obtain a viscous isocyanate-terminated fluorinated polyurethane FPU-2, and then a viscous fluorinated balloon FPU was obtained (the preparation method was the same as in Example 1).

[0087] Take 20g of polybutylene adipate (Mn=2000) dissolved in 30mlN,N-dimethylformamide and subjected to vacuum dehydration treatment at 100°C for 2 hours, add it to a 100ml three-necked flask dried in a blast oven and treated with nitrogen, add 5g of diphenylmethane diisocyanate, react at 80°C for 2h, and obtain a viscous isocyanate-terminated polyurethane prepolymer PU-1; add 2.28g of propylene glycol dissolved in 2.5ml of N,N-dimethylformamide, react at 60°C for 1h, and obtain a viscous transparent polyurethane PU-2; then add 13.64g of a fluorine-modified balloon dissolved in 5ml of N,N-dimethylformamide, stir the system at 40°C for 30min to make it evenly dispersed, and obtain a viscous fluorine-modified balloon-coated crosslinker polyurethane viscosity-reducing adhesive.

[0088] The shear strength of the viscosity-reducing adhesive was measured to be 3.26 MPa, and the shear strength after hot and cold shock was 0.17 MPa.

[0089] Embodiment 15

[0090] 20 g of polybutylene adipate (Mn=1000) which had been subjected to vacuum dehydration treatment at 100° C. for 2 hours and dissolved in 30 ml of N,N-dimethylformamide was added to a 100 ml three-necked flask which had been dried in a blast oven and treated with nitrogen, 10 g of diphenylmethane diisocyanate and 0.03 g of an organic tin catalyst were added, and the mixture was reacted at 80° C. for 2 hours to obtain a viscous isocyanate-terminated polyurethane prepolymer FPU-1; 2.12 g of hexafluoropentanediol dissolved in 2.5 ml of N,N-dimethylformamide was added, and the mixture was reacted at 80° C. for 1 hour to obtain a viscous isocyanate-terminated fluorinated polyurethane FPU-2, and then a viscous fluorinated balloon FPU was obtained (the preparation method was the same as in Example 1).

[0091] Take 20g of polybutylene adipate (Mn=1000) dissolved in 30mlN,N-dimethylformamide and dehydrated in vacuum at 100°C for 2 hours, add it to a 100ml three-necked flask dried in a blast oven and treated with nitrogen, add 10g of diphenylmethane diisocyanate, react at 80°C for 2h, and obtain a viscous isocyanate-terminated polyurethane prepolymer PU-1; add 7.08g of 1,6-hexanediol dissolved in 2.5ml of N,N-dimethylformamide, react at 60°C for 1h, and obtain a viscous transparent polyurethane PU-2; then add 18.54g of a fluorine-modified balloon dissolved in 5ml of N,N-dimethylformamide, stir the system at 40°C for 30min to make it evenly dispersed, and obtain a viscous fluorine-modified balloon coated with a crosslinker polyurethane viscosity-reducing adhesive.

[0092] The shear strength of the viscosity-reducing adhesive was measured to be 3.42 MPa, and the shear strength after hot and cold shock was 0.11 MPa.

[0093] Example 16

[0094] 20 g of polytetrahydrofuran diol (Mn=2000) dissolved in 30 ml of N,N-dimethylformamide and subjected to vacuum dehydration treatment at 100° C. for 2 hours was added to a 100 ml three-necked flask dried in a blast oven and treated with nitrogen, 5 g of diphenylmethane diisocyanate and 0.03 g of an organic tin catalyst were added, and the mixture was reacted at 80° C. for 2 hours to obtain a viscous isocyanate-terminated polyurethane prepolymer FPU-1; 1.62 g of tetrafluorobutanediol dissolved in 2.5 ml of N,N-dimethylformamide was added, and the mixture was reacted at 80° C. for 1 hour to obtain a viscous isocyanate-terminated fluorinated polyurethane FPU-2, and then a viscous fluorinated balloon FPU was obtained (the preparation method was the same as in Example 1).

[0095] 20 g of polyethylene adipate (Mn=2000) dissolved in 30 ml of N, N-dimethylformamide and subjected to vacuum dehydration treatment at 100 ° C for 2 hours was added to a 100 ml three-necked flask dried in a blast oven and treated with nitrogen, and 3.48 g of 2,4-toluene diisocyanate was added, and the reaction was carried out at 80 ° C for 2 hours to obtain a viscous isocyanate-terminated polyurethane prepolymer PU-1; 3.54 g of 1,6-hexanediol dissolved in 2.5 ml of N, N-dimethylformamide was added, and the reaction was carried out at 60 ° C for 1 hour to obtain a viscous transparent polyurethane PU-2; 13.51 g of a fluorine-modified balloon dissolved in 5 ml of N, N-dimethylformamide was added, and the system was stirred at 40 ° C for 30 minutes to make it evenly dispersed, and a viscous fluorine-modified balloon-coated crosslinker polyurethane viscosity-reducing adhesive was obtained.

[0096] The shear strength of the viscosity-reducing adhesive was measured to be 3.06 MPa, and the shear strength after hot and cold shock was 0.17 MPa.

[0097] Embodiment 17

[0098] 20 g of polycaprolactone diol (Mn=1000) which had been subjected to vacuum dehydration treatment at 100° C. for 2 hours and dissolved in 30 ml of N,N-dimethylformamide was added into a 100 ml three-necked flask which had been dried in a blast oven and treated with nitrogen, 10 g of diphenylmethane diisocyanate and 0.03 g of an organic tin catalyst were added, and the mixture was reacted at 80° C. for 2 hours to obtain a viscous isocyanate-terminated polyurethane prepolymer FPU-1; 5.24 g of octafluorohexanediol dissolved in 2.5 ml of N,N-dimethylformamide was added, and the mixture was reacted at 80° C. for 1 hour to obtain a viscous isocyanate-terminated fluorinated polyurethane FPU-2, and then a viscous fluorinated balloon FPU was obtained (the preparation method was the same as in Example 1).

[0099] 20 g of polyethylene adipate (Mn=2000) dissolved in 30 ml N, N-dimethylformamide and subjected to vacuum dehydration treatment at 100 ° C for 2 hours was added to a 100 ml three-necked flask dried in a blast oven and treated with nitrogen, and 3.48 g of 2,4-toluene diisocyanate was added, and the reaction was carried out at 80 ° C for 2 hours to obtain a viscous isocyanate-terminated polyurethane prepolymer PU-1; 3.54 g of 1,6-hexanediol dissolved in 2.5 ml N, N-dimethylformamide was added, and the reaction was carried out at 60 ° C for 1 hour to obtain a viscous transparent polyurethane PU-2; 13.51 g of fluorine-modified balloon dissolved in 5 ml N, N-dimethylformamide was added, and the system was stirred at 40 ° C for 30 minutes to make it uniformly dispersed, and a viscous fluorine-modified balloon coated with a crosslinker polyurethane viscosity-reducing adhesive was obtained.

[0100] The shear strength of the viscosity-reducing adhesive was measured to be 3.14 MPa, and the shear strength after hot and cold shock was 0.22 MPa.

[0101] Embodiment 18

[0102] Take 20g of polycaprolactone diol (Mn=2000) dissolved in 30mlN,N-dimethylformamide and subjected to vacuum dehydration treatment at 100°C for 2 hours, add it into a 100ml three-necked flask that has been dried in a blast oven and treated with nitrogen, add 3.36g of hexamethylene diisocyanate and 0.03g of an organic tin catalyst, and react at 80°C for 2h to obtain a viscous isocyanate-terminated polyurethane prepolymer FPU-1; add 1.62g of tetrafluorobutanediol dissolved in 2.5mlN,N-dimethylformamide, and react at 80°C for 1h to obtain a viscous isocyanate-terminated fluorine-containing polyurethane FPU-2, and then, obtain a viscous fluorine-containing balloon FPU (preparation method is the same as Example 1).

[0103] 20 g of polyethylene adipate (Mn=2000) dissolved in 30 ml N, N-dimethylformamide and subjected to vacuum dehydration treatment at 100 ° C for 2 hours was added to a 100 ml three-necked flask dried in a blast oven and treated with nitrogen, and 3.48 g of 2,6-toluene diisocyanate was added, and the reaction was carried out at 80 ° C for 2 hours to obtain a viscous isocyanate-terminated polyurethane prepolymer PU-1; 3.54 g of 1,6-hexanediol dissolved in 2.5 ml N, N-dimethylformamide was added, and the reaction was carried out at 60 ° C for 1 hour to obtain a viscous transparent polyurethane PU-2; 13.51 g of fluorine-modified balloon dissolved in 5 ml N, N-dimethylformamide was added, and the system was stirred at 40 ° C for 30 minutes to make it evenly dispersed, and a viscous fluorine-modified balloon coated with a crosslinker polyurethane viscosity-reducing adhesive was obtained.

[0104] The shear strength of the viscosity-reducing adhesive was measured to be 3.37 MPa, and the shear strength after hot and cold shock was 1.04 MPa.

[0105] Comparative Example 1

[0106] Take 20g of polytetrahydrofuran diol (Mn=1000) dissolved in 30mlN,N-dimethylformamide and dehydrated in vacuum at 100°C for 2 hours, add it to a 100ml three-necked flask dried in a blast oven and treated with nitrogen, add 8.88g of isophorone diisocyanate, react at 80°C for 2h to obtain a viscous isocyanate-terminated polyurethane prepolymer PU-1; add 5.4g of 1,4-butanediol in 2.5ml of N,N-dimethylformamide, react at 60°C for 1h to obtain a viscous viscosity-reducing adhesive modified without fluorine-containing balloons.

[0107] The shear strength of the viscosity-reducing adhesive was measured to be 3.21 MPa, and the shear strength after hot and cold shock was 3.42 MPa.

[0108] Comparative Example 2

[0109] 20 g of polycaprolactone diol (Mn=2000) dissolved in 30 ml of N,N-dimethylformamide and subjected to vacuum dehydration treatment at 100° C. for 2 hours was added to a 100 ml three-necked flask dried in a blast oven and treated with nitrogen, 3.36 g of hexamethylene diisocyanate and 0.03 g of an organic tin catalyst were added, and the mixture was reacted at 80° C. for 2 hours to obtain a viscous isocyanate-terminated polyurethane prepolymer FPU-1; 1.6 g of 2,6-difluoro-4-hydroxybenzyl alcohol dissolved in 2.5 ml of N,N-dimethylformamide was added, and the mixture was reacted at 80° C. for 1 hour to obtain a viscous isocyanate-terminated fluorinated polyurethane FPU-2, and then a viscous fluorinated balloon FPU was obtained (the preparation method is the same as that in Example 1).

[0110] 20 g of polycaprolactone diol (Mn=2000) dissolved in 30 ml N, N-dimethylformamide and subjected to vacuum dehydration treatment at 100 ° C for 2 hours was added to a 100 ml three-necked flask dried in a blast oven and treated with nitrogen, and 3.48 g of 2,4-toluene diisocyanate was added, and the reaction was carried out at 80 ° C for 2 hours to obtain a viscous isocyanate-terminated polyurethane prepolymer PU-1; 3.54 g of 1,6-hexanediol dissolved in 2.5 ml N, N-dimethylformamide was added, and the reaction was carried out at 60 ° C for 1 hour to obtain a viscous transparent polyurethane PU-2; 13.51 g of fluorine-modified balloon dissolved in 5 ml N, N-dimethylformamide was added, and the system was stirred at 40 ° C for 30 minutes to make it evenly dispersed, and a viscous fluorine-modified balloon coated with a crosslinker polyurethane viscosity-reducing adhesive was obtained.

[0111] The shear strength of the viscosity-reducing adhesive was measured to be 3.04 MPa, and the shear strength after hot and cold shock was 2.44 MPa.

Claims

1. A method for preparing a polyurethane viscosity-reducing adhesive, characterized in that: The preparation method steps are as follows: (1) adding isocyanate, an organic tin catalyst, and an organic solvent to a dehydrated bifunctional polyol, reacting at 75-85° C. for 2 h to obtain a viscous isocyanate-terminated polyurethane prepolymer FPU-1; (2) dissolving the fluorinated polyol in an organic solvent, adding the solution to the FPU-1 in step (1), and reacting at 75-85° C. for 1 h to obtain a viscous isocyanate-terminated fluorinated polyurethane FPU-2; (3) FPU-2 is placed as a wall material in the gap between the inner and outer walls of a concentric metal tube, and is blown into the tube by gas. Isocyanate, as a core material, naturally falls from the inside and forms droplets after being wrapped. After solidification, it forms a crosslinking agent coated with a fluorine-modified balloon; (4) adding isocyanate, an organic tin catalyst, and an organic solvent to the dehydrated bifunctional polyol, reacting at 75-85° C. for 2 h to obtain a viscous isocyanate-terminated polyurethane prepolymer PU-1; (5) dissolving a small molecule diol chain extender in an organic solvent and adding the resultant to the PU-1 of step (4), and reacting the system at 55-65° C. for 1 h to extend the chain, thereby obtaining a viscous hydroxyl-terminated polyurethane PU-2; (6) Adding a fluorine-modified balloon-coated crosslinking agent dissolved in an organic solvent to PU-2, stirring the system at 35-45° C. for 30 min to uniformly disperse it, thereby obtaining a viscous polyurethane adhesive containing a fluorine-modified balloon-coated crosslinking agent.

2. The method for preparing the polyurethane viscosity-reducing adhesive according to claim 1, characterized in that: In steps (1), (3) and (4), the isocyanate is one of isophorone diisocyanate, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, diphenylmethane diisocyanate, dicyclohexylmethane diisocyanate and hexamethylene diisocyanate.

3. The method for preparing the polyurethane viscosity-reducing adhesive according to claim 1, characterized in that: In step (2), the fluorine-containing polyol is one of tetrafluorobutanediol, hexafluoropentanediol and octafluorohexanediol; and the molar ratio of the fluorine-containing polyol to the difunctional polyol is 1:

1.

4. The method for preparing the polyurethane viscosity-reducing adhesive according to claim 1, characterized in that: In steps (1) and (4), the difunctional polyol is one of polytetrahydrofuran diol, polyethylene adipate, polybutylene adipate, polyhexane adipate or polycaprolactone diol, M n =500-5000; the molar ratio of the difunctional polyol to the isocyanate is 1:2; the organic tin catalyst is dibutyltin dilaurate or stannous octoate, and the amount of the organic tin catalyst is 0.25-0.5 of the mass of the difunctional polyol. w t%.

5. The method for preparing the polyurethane viscosity-reducing adhesive according to claim 1, characterized in that: In step (3), the mass ratio of the wall material to the core material is 3:

1.

6. The method for preparing the polyurethane viscosity-reducing adhesive according to claim 1, characterized in that: In step (5), the small molecule diol chain extender is one of 1,4-butanediol, propylene glycol, 1,6-hexanediol, ethylene glycol, and neopentyl glycol; and the molar ratio of the small molecule diol chain extender to the difunctional polyol is 3:

1.

7. The method for preparing the polyurethane viscosity-reducing adhesive according to claim 1, characterized in that: In steps (1)-(2) and (4)-(6), the organic solvent is one of: N,N-dimethylformamide, acetone, ethyl acetate, and butyl acetate.

8. The method for preparing the polyurethane viscosity-reducing adhesive according to claim 1, characterized in that: In step (6), the mass ratio of PU-2 to the crosslinking agent for coating the fluorine-modified balloon is 2:

1.

9. A polyurethane viscosity-reducing adhesive prepared by the method according to any one of claims 1 to 8, characterized in that: The general structural formula of the polyurethane viscosity-reducing adhesive is as follows: HO-R2-OOCNH-R1-NHCOO-R2-OOCNH-R1-NHCOO-R2-OOCNH-R1-NHCOO-R2-OH Here, -NHCOO- can be replaced by -NHCONH-.

10. An application of the polyurethane viscosity-reducing adhesive prepared by the method according to any one of claims 1 to 8, characterized in that: The polyurethane viscosity-reducing adhesive is applied to PACK adhesive of power batteries.

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