TPU (thermoplastic polyurethane) film containing carbon nanotubes and application of TPU film

Abstract

The invention relates to a TPU (thermoplastic polyurethane) film containing carbon nanotubes and application of the TPU film, and belongs to the technical field of TPU films. According to the invention, zinc chloride and lactic acid are respectively used as HBA and HBD to prepare a deep-eutectic solvent, the deep-eutectic solvent is coupled with hydrogen peroxide to pre-treat carbon nanotubes, surface polar groups are constructed, and then based on condensation of an amino coupling agent, amino groups are modified, so that the carbon nanotubes are prepared. Then, a polymer obtained through copolymerization of allyl benzene, glycidyl methacrylate and methyl acrylate is used as a modifier, amino-epoxy group ring-opening addition is carried out, so that modified carbon nanotubes are prepared, the modified carbon nanotubes and a first thermoplastic polyurethane elastomer are subjected to melt blending, coating and other operations in sequence, and then a first film layer is formed; one side of the first film layer is coated with the film-forming liquid prepared from the second thermoplastic polyurethane elastomer, the insulating agent, the flame retardant and the N, N-dimethylformamide, and finally the TPU film is obtained after drying, the dispersity of the carbon nanotubes is good, and the heating efficiency of the TPU film is high.

Description

Technical Field

[0001] The invention belongs to the technical field of TPU films, and in particular relates to a TPU film containing carbon nanotubes and applications thereof. Background Art

[0002] Carbon nanotubes, also known as buckytubes, are one-dimensional quantum materials with a special structure. Their radial dimensions are in the nanometer range, their axial dimensions are in the micrometer range, and both ends of the tubes are basically sealed. A large number of studies have shown that carbon nanotubes have excellent electrical and thermal properties. Some metallic carbon nanotubes can exhibit electrical conductivity comparable to that of metals, while the thermal conductivity of carbon nanotubes calculated based on theoretical simulations and indirect experiments is approximately in the range of 2000-6000W / (m·K). For this reason, many polymer materials such as TPU will add carbon nanotubes to prepare electric heating films for use in thermal insulation products. However, these electric heating films still have certain drawbacks that limit their actual application effects. This is because the agglomeration of carbon nanotubes is very serious and their dispersibility in polymer materials is extremely poor, which seriously reduces the heating efficiency of the final electric heating films. Summary of the invention

[0003] In view of the problems existing in the prior art, the purpose of the present invention is to provide a TPU film containing carbon nanotubes and its application. The present invention uses zinc chloride and lactic acid as HBA and HBD respectively to prepare a low eutectic solvent, which is coupled with hydrogen peroxide to pre-treat carbon nanotubes to construct surface polar groups, and then based on the condensation of amino coupling agents, the amino groups are modified, and then a polymer obtained by copolymerization of styrene, glycidyl methacrylate and methyl acrylate is used as a modifier to cause amino-epoxy ring-opening addition, thereby preparing modified carbon nanotubes, which are melt-blended, coated and other operations with a first thermoplastic polyurethane elastomer to form a first film layer, and a film-forming liquid prepared by a second thermoplastic polyurethane elastomer, an insulating agent, a flame retardant and N,N-dimethylformamide is coated on one side of the first film layer, and finally a TPU film is obtained after drying, and the carbon nanotubes have good dispersibility and high heating efficiency.

[0004] The purpose of the present invention can be achieved through the following technical solutions:

[0005] A method for preparing a TPU film containing carbon nanotubes, the preparation method comprising the following steps:

[0006] Step A: mixing the first thermoplastic polyurethane elastomer and the modified carbon nanotubes at a mass ratio of 80-85:15-20 at 190-200° C. for 8-10 minutes, coating, and naturally cooling to room temperature to obtain a first film layer;

[0007] Step B: adding 30 parts by weight of a second thermoplastic polyurethane elastomer, 0.3-0.5 parts by weight of an insulating agent and 8-10 parts by weight of a flame retardant to 100 parts by weight of N,N-dimethylformamide, and then stirring and mixing at 60-70° C. for 12 hours in ultrasound to obtain a film-forming solution;

[0008] Step C: coating the film-forming liquid on one side of the first film layer, drying, and naturally cooling to room temperature, and the preparation is completed.

[0009] As a preferred technical solution of the present invention, the modified carbon nanotubes described in step A are prepared by the following steps:

[0010] (1) adding 8-10 parts by weight of hydrogen peroxide to 80-100 parts by weight of a low eutectic solvent, stirring and mixing at room temperature for 5-10 minutes, then adding 4 parts by weight of carbon nanotubes, stirring and mixing at room temperature for 24 hours, filtering, taking the filter residue, washing with deionized water, and finally vacuum drying at 60-80° C. until constant weight, to obtain component A;

[0011] (2) adding 1-2 parts by weight of deionized water, the component A and 5-6 parts by weight of an amino coupling agent to 120 parts by weight of ethyl acetate, stirring and mixing at 70-75° C. for 12-14 hours, filtering, taking the filter residue, washing it with deionized water, and finally vacuum drying it at 60-80° C. until constant weight, to obtain component B;

[0012] (3) adding 1 part by weight of styrene, 0.5-1 part by weight of glycidyl methacrylate and 3-4 parts by weight of methyl acrylate to 120 parts by weight of N,N-dimethylformamide, and then adding dropwise 13-15 parts by weight of azobisisobutyronitrile solution at 60-70° C. with stirring. After all the addition is completed, continue stirring at a constant temperature for 8-10 hours to obtain component C;

[0013] (4) Adding component B to component C, stirring at 70-75° C. for 4-6 hours, filtering, taking the filter residue, washing with deionized water, and finally vacuum drying at 60-80° C. until constant weight, the preparation is completed.

[0014] Furthermore, the deep eutectic solvent in step (1) is prepared by the following steps:

[0015] Zinc chloride and lactic acid are mixed at a molar ratio of 1:7-10 at 80-90°C for 12 hours with stirring, and the mixture is naturally cooled to room temperature to complete the preparation.

[0016] Furthermore, the amino coupling agent in step (2) is 3-aminopropyltrimethoxysilane.

[0017] Furthermore, the dripping rate in step (3) is controlled at 1-2 drops / s.

[0018] Furthermore, the azobisisobutyronitrile solution in step (3) is prepared by the following steps:

[0019] Azobisisobutyronitrile and N,N-dimethylformamide are mixed at a mass ratio of 1:30-40 and stirred for 10-15 minutes at room temperature to complete the preparation.

[0020] As a preferred technical solution of the present invention, in step A, the thickness of the first film layer is 60-65 μm.

[0021] As a preferred technical solution of the present invention, the insulating agent in step B is nano-silicon dioxide.

[0022] As a preferred technical solution of the present invention, the flame retardant in step B is a molecular sieve.

[0023] As a preferred technical solution of the present invention, the power of the ultrasound in step B is 300-400W.

[0024] As a preferred technical solution of the present invention, the drying in step C refers to drying at 85-90° C. for 40 minutes.

[0025] A TPU film containing carbon nanotubes prepared by the preparation method as described above.

[0026] As a preferred technical solution of the present invention, the thickness of the TPU film containing carbon nanotubes is 90-100 μm.

[0027] An application of a TPU film containing carbon nanotubes prepared by the preparation method as described above, wherein the TPU film containing carbon nanotubes is applied to thermal insulation products.

[0028] Beneficial effects of the present invention:

[0029] (1) The present invention uses zinc chloride and lactic acid as HBA and HBD, respectively, to prepare a low eutectic solvent, which is coupled with hydrogen peroxide to pre-treat carbon nanotubes to construct surface polar groups, and then based on the condensation of amino coupling agents, the amino groups are modified, and then a polymer obtained by copolymerization of styrene, glycidyl methacrylate and methyl acrylate is used as a modifier to cause amino-epoxy ring-opening addition, thereby preparing modified carbon nanotubes, which are melt-blended and coated with a first thermoplastic polyurethane elastomer to form a first film layer, and a film-forming liquid prepared by a second thermoplastic polyurethane elastomer, an insulating agent, a flame retardant and N,N-dimethylformamide is coated on one side of the first film layer, and finally a TPU film is obtained after drying, and the carbon nanotubes have good dispersibility and high heating efficiency.

[0030] (2) The present invention uses zinc chloride and lactic acid to prepare a low eutectic solvent, which is coupled with hydrogen peroxide to pretreat carbon nanotubes, constructing surface polar oxygen-containing groups, thereby promoting the dispersion of carbon nanotubes in polar polymer TPU to a certain extent. Compared with the prior art using strong acid solutions such as sulfuric acid, nitric acid, etc. for pretreatment, the pretreatment method of the present invention can effectively reduce the damage to the carbon nanotube structure and maintain its inherent excellent performance as much as possible. On this basis, the dispersibility of carbon nanotubes is still limited. For this reason, an amino coupling agent is first added for condensation to modify the amino group to provide a site for further modification treatment, and then a polymer obtained by copolymerization of styrene, glycidyl methacrylate and methyl acrylate is used as a modifier to cause amino-epoxy ring-opening addition. On the one hand, the steric hindrance of the polymer structure is large, which can achieve the dispersion of carbon nanotubes and reduce agglomeration. On the other hand, the main role of the glycidyl methacrylate monomer in the polymer structure is to provide epoxy groups, and the methyl acrylate monomer can form hydrogen bonds with the -NH group of TPU by virtue of its own -C=O group, thereby improving the compatibility of the two and further promoting the dispersion effect. As for the styrene monomer, due to its rigid structure of benzene ring and strong intermolecular force, it can effectively ensure that the polymer structure will not be destroyed or degraded due to high temperature during subsequent melt blending. Finally, the prepared modified carbon nanotubes have excellent dispersibility in the TPU matrix, which improves the heating efficiency of the TPU film and is very suitable for application in the field of thermal insulation products. DETAILED DESCRIPTION

[0031] In order to further illustrate the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the specific implementation methods, structures, features and effects of the present invention are described in detail below in combination with the embodiments.

[0032] The sources of the raw materials in the embodiments and comparative examples are as follows: the first thermoplastic polyurethane elastomers were purchased from Bayer, Germany, with model number 95A; the second thermoplastic polyurethane elastomers were purchased from Wanhua Chemical Group Co., Ltd., with model number WHT-1185EC; the carbon nanotubes were purchased from Shanghai Xiangtian Nanomaterial Co., Ltd., with model number XT-C1-02; the nano-silicon dioxide was purchased from Shanghai Xiangtian Nanomaterial Co., Ltd., with model number XT-SI02-02; the molecular sieves were purchased from Jiangxi Xintao Technology Co., Ltd., and the product name was 5A molecular sieve activation powder.

[0033] Example 1

[0034] A method for preparing a TPU film containing carbon nanotubes, the preparation method comprising the following steps:

[0035] Step A: mixing the first thermoplastic polyurethane elastomer and the modified carbon nanotubes at a mass ratio of 80:15 at 190° C. for 8 minutes, coating, and naturally cooling to room temperature to obtain a first film layer;

[0036] Step B: adding 30 parts by weight of a second thermoplastic polyurethane elastomer, 0.3 parts by weight of an insulating agent and 8 parts by weight of a flame retardant to 100 parts by weight of N,N-dimethylformamide, and then stirring and mixing at 60° C. for 12 hours in ultrasound to obtain a film-forming solution;

[0037] Step C: coating the film-forming liquid on one side of the first film layer, drying, and naturally cooling to room temperature, and the preparation is completed.

[0038] The modified carbon nanotubes described in step A are prepared by the following steps:

[0039] (1) adding 8 parts by weight of hydrogen peroxide to 80 parts by weight of a low eutectic solvent, stirring and mixing at room temperature for 5 minutes, then adding 4 parts by weight of carbon nanotubes, stirring and mixing at room temperature for 24 hours, filtering, taking the filter residue, washing with deionized water, and finally vacuum drying at 60° C. until constant weight, to obtain component A;

[0040] (2) adding 1 part by weight of deionized water, the component A and 5 parts by weight of an amino coupling agent to 120 parts by weight of ethyl acetate, stirring and mixing at 70° C. for 12 h, filtering, taking the filter residue, washing it with deionized water, and finally vacuum drying it at 60° C. until constant weight, to obtain component B;

[0041] (3) Add 1 part by weight of styrene, 0.5 parts by weight of glycidyl methacrylate and 3 parts by weight of methyl acrylate to 120 parts by weight of N,N-dimethylformamide, and then dropwise add 13 parts by weight of azobisisobutyronitrile solution at 60° C. while stirring. After all the addition is completed, continue to stir at constant temperature for 8 hours to obtain component C;

[0042] (4) Adding component B to component C, stirring and mixing at 70° C. for 4 h, filtering, taking the filter residue, washing with deionized water, and finally vacuum drying at 60° C. until constant weight, the preparation is completed.

[0043] The deep eutectic solvent in step (1) is prepared by the following steps:

[0044] Zinc chloride and lactic acid were mixed at a molar ratio of 1:7 at 80° C. with stirring for 12 h, and naturally cooled to room temperature to complete the preparation.

[0045] The amino coupling agent in step (2) is 3-aminopropyltrimethoxysilane.

[0046] The dripping rate in step (3) is controlled at 1 drop / s.

[0047] The azobisisobutyronitrile solution in step (3) is prepared by the following steps:

[0048] Azobisisobutyronitrile and N,N-dimethylformamide are mixed at a mass ratio of 1:30 and stirred for 10 minutes at room temperature to complete the preparation.

[0049] In step A, the thickness of the first film layer is 60 μm.

[0050] The insulating agent in step B is nano silicon dioxide.

[0051] The flame retardant in step B is a molecular sieve.

[0052] The power of the ultrasound in step B is 300W.

[0053] The drying in step C refers to drying at 85° C. for 40 min.

[0054] A TPU film containing carbon nanotubes prepared by the preparation method as described above.

[0055] The thickness of the TPU film containing carbon nanotubes is 90 μm.

[0056] An application of a TPU film containing carbon nanotubes prepared by the preparation method as described above, wherein the TPU film containing carbon nanotubes is applied to thermal insulation products.

[0057] Example 2

[0058] A method for preparing a TPU film containing carbon nanotubes, the preparation method comprising the following steps:

[0059] Step A: mixing the first thermoplastic polyurethane elastomer and the modified carbon nanotubes at a mass ratio of 85:20 at 200° C. for 10 min, coating, and naturally cooling to room temperature to obtain a first film layer;

[0060] Step B: adding 30 parts by weight of a second thermoplastic polyurethane elastomer, 0.5 parts by weight of an insulating agent and 10 parts by weight of a flame retardant to 100 parts by weight of N,N-dimethylformamide, and then stirring and mixing at 70° C. for 12 hours in ultrasound to obtain a film-forming solution;

[0061] Step C: coating the film-forming liquid on one side of the first film layer, drying, and naturally cooling to room temperature, and the preparation is completed.

[0062] The modified carbon nanotubes described in step A are prepared by the following steps:

[0063] (1) adding 10 parts by weight of hydrogen peroxide to 100 parts by weight of a low eutectic solvent, stirring and mixing at room temperature for 10 minutes, then adding 4 parts by weight of carbon nanotubes, stirring and mixing at room temperature for 24 hours, filtering, taking the filter residue, washing with deionized water, and finally vacuum drying at 80° C. until constant weight, to obtain component A;

[0064] (2) adding 2 parts by weight of deionized water, the component A and 6 parts by weight of an amino coupling agent to 120 parts by weight of ethyl acetate, stirring and mixing at 75° C. for 14 h, filtering, taking the filter residue, washing it with deionized water, and finally vacuum drying it at 80° C. until constant weight, to obtain component B;

[0065] (3) Add 1 part by weight of styrene, 1 part by weight of glycidyl methacrylate and 4 parts by weight of methyl acrylate to 120 parts by weight of N,N-dimethylformamide, and then dropwise add 15 parts by weight of azobisisobutyronitrile solution at 70° C. while stirring. After all the addition is completed, continue to stir at constant temperature for 10 hours to obtain component C;

[0066] (4) Adding component B to component C, stirring and mixing at 75° C. for 6 h, filtering, taking the filter residue, washing with deionized water, and finally vacuum drying at 80° C. until constant weight, the preparation is completed.

[0067] The deep eutectic solvent in step (1) is prepared by the following steps:

[0068] Zinc chloride and lactic acid were mixed at a molar ratio of 1:10 at 90° C. with stirring for 12 h, and naturally cooled to room temperature to complete the preparation.

[0069] The amino coupling agent in step (2) is 3-aminopropyltrimethoxysilane.

[0070] The dripping rate in step (3) is controlled at 2 drops / s.

[0071] The azobisisobutyronitrile solution in step (3) is prepared by the following steps:

[0072] Azobisisobutyronitrile and N,N-dimethylformamide are mixed at a mass ratio of 1:40 at room temperature and stirred for 15 minutes to complete the preparation.

[0073] In step A, the thickness of the first film layer is 65 μm.

[0074] The insulating agent in step B is nano silicon dioxide.

[0075] The flame retardant in step B is a molecular sieve.

[0076] The power of the ultrasound in step B is 400W.

[0077] The drying in step C refers to drying at 90° C. for 40 min.

[0078] A TPU film containing carbon nanotubes prepared by the preparation method as described above.

[0079] The thickness of the TPU film containing carbon nanotubes is 100 μm.

[0080] An application of a TPU film containing carbon nanotubes prepared by the preparation method as described above, wherein the TPU film containing carbon nanotubes is applied to thermal insulation products.

[0081] Example 3

[0082] A method for preparing a TPU film containing carbon nanotubes, the preparation method comprising the following steps:

[0083] Step A: mixing the first thermoplastic polyurethane elastomer and the modified carbon nanotubes at a mass ratio of 83:18 at 195° C. for 9 minutes, coating, and naturally cooling to room temperature to obtain a first film layer;

[0084] Step B: adding 30 parts by weight of a second thermoplastic polyurethane elastomer, 0.4 parts by weight of an insulating agent and 9 parts by weight of a flame retardant to 100 parts by weight of N,N-dimethylformamide, and then stirring and mixing at 65° C. for 12 hours in ultrasound to obtain a film-forming solution;

[0085] Step C: coating the film-forming liquid on one side of the first film layer, drying, and naturally cooling to room temperature, and the preparation is completed.

[0086] The modified carbon nanotubes described in step A are prepared by the following steps:

[0087] (1) adding 9 parts by weight of hydrogen peroxide to 90 parts by weight of a low eutectic solvent, stirring and mixing at room temperature for 8 minutes, then adding 4 parts by weight of carbon nanotubes, stirring and mixing at room temperature for 24 hours, filtering, taking the filter residue, washing with deionized water, and finally vacuum drying at 70° C. until constant weight, to obtain component A;

[0088] (2) adding 1.5 parts by weight of deionized water, the component A and 5.5 parts by weight of an amino coupling agent to 120 parts by weight of ethyl acetate, stirring and mixing at 73° C. for 13 h, filtering, taking the filter residue, washing it with deionized water, and finally vacuum drying it at 70° C. until constant weight, to obtain component B;

[0089] (3) Add 1 part by weight of styrene, 0.8 parts by weight of glycidyl methacrylate and 3.5 parts by weight of methyl acrylate to 120 parts by weight of N,N-dimethylformamide, and then dropwise add 14 parts by weight of azobisisobutyronitrile solution at 65° C. while stirring. After all the addition is completed, continue to stir at constant temperature for 9 hours to obtain component C;

[0090] (4) Adding component B to component C, stirring and mixing at 73° C. for 5 h, filtering, taking the filter residue, washing with deionized water, and finally vacuum drying at 70° C. until constant weight, the preparation is completed.

[0091] The deep eutectic solvent in step (1) is prepared by the following steps:

[0092] Zinc chloride and lactic acid were mixed at a molar ratio of 1:8 at 85° C. with stirring for 12 h, and naturally cooled to room temperature to complete the preparation.

[0093] The amino coupling agent in step (2) is 3-aminopropyltrimethoxysilane.

[0094] The dripping rate in step (3) is controlled at 1.5 drops / s.

[0095] The azobisisobutyronitrile solution in step (3) is prepared by the following steps:

[0096] Azobisisobutyronitrile and N,N-dimethylformamide are mixed at a mass ratio of 1:35 at room temperature and stirred for 13 minutes to complete the preparation.

[0097] In step A, the thickness of the first film layer is 62 μm.

[0098] The insulating agent in step B is nano silicon dioxide.

[0099] The flame retardant in step B is a molecular sieve.

[0100] The power of the ultrasound in step B is 350W.

[0101] The drying in step C refers to drying at 88° C. for 40 min.

[0102] A TPU film containing carbon nanotubes prepared by the preparation method as described above.

[0103] The thickness of the TPU film containing carbon nanotubes is 95 μm.

[0104] An application of a TPU film containing carbon nanotubes prepared by the preparation method as described above, wherein the TPU film containing carbon nanotubes is applied to thermal insulation products.

[0105] Comparative Example 1

[0106] On the basis of Example 3, the low eutectic solvent and hydrogen peroxide in step (1) were changed to aqueous nitric acid solution with an equal weight concentration of 2 mol / L, and at the same time, stirring and mixing at room temperature for 24 h was changed to stirring and mixing at room temperature for 1 h, and the rest remained unchanged.

[0107] Comparative Example 2

[0108] Based on Example 3, step (2), step (3) and step (4) are not performed, and the rest remain unchanged.

[0109] Comparative Example 3

[0110] Based on Example 3, styrene was not added in step (3), and the rest remained unchanged.

[0111] Comparative Example 4

[0112] Based on Example 3, methyl acrylate was not added in step (3), and the rest remained unchanged.

[0113] Comparative Example 5

[0114] Based on Example 3, the hydrogen peroxide in step (1) was replaced by an equal weight of a low eutectic solvent, and the rest remained unchanged.

[0115] Test Example 1

[0116] Heating efficiency test:

[0117] Conductive copper tapes were attached to the carbon nanotube-containing TPU films prepared in Example 3 and Comparative Examples 1-5, respectively, and then powered on at 30 V for 100 s (at room temperature), and the temperature after power-on was recorded (rounded to an integer).

[0118] Table 1. Heating efficiency test results

[0119] Temperature / ℃ Example 3 57 Comparative Example 1 51 Comparative Example 2 44 Comparative Example 3 48 Comparative Example 4 50 Comparative Example 5 53

[0120] From the comparison between Example 3 and Comparative Examples 1-5 in Test Example 1, it can be seen that the TPU film containing carbon nanotubes prepared by the present invention has a more excellent heating efficiency, which indirectly indicates that the dispersion of its carbon nanotubes is also stronger.

[0121] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technical personnel in this field can make some changes or modify the technical contents disclosed above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any brief modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A method for preparing a TPU film containing carbon nanotubes, characterized in that: The preparation method comprises the following steps: Step A: mixing the first thermoplastic polyurethane elastomer and the modified carbon nanotubes at a mass ratio of 80-85:15-20 at 190-200° C. for 8-10 minutes, coating, and naturally cooling to room temperature to obtain a first film layer; Step B: adding 30 parts by weight of a second thermoplastic polyurethane elastomer, 0.3-0.5 parts by weight of an insulating agent and 8-10 parts by weight of a flame retardant to 100 parts by weight of N,N-dimethylformamide, and then stirring and mixing at 60-70° C. for 12 hours in ultrasound to obtain a film-forming solution; Step C: coating the film-forming liquid on one side of the first film layer, drying, and naturally cooling to room temperature, and the preparation is completed.

2. The method for preparing a TPU film containing carbon nanotubes according to claim 1, characterized in that: The modified carbon nanotubes described in step A are prepared by the following steps: (1) adding 8-10 parts by weight of hydrogen peroxide to 80-100 parts by weight of a low eutectic solvent, stirring and mixing at room temperature for 5-10 minutes, then adding 4 parts by weight of carbon nanotubes, stirring and mixing at room temperature for 24 hours, filtering, taking the filter residue, washing with deionized water, and finally vacuum drying at 60-80° C. until constant weight, to obtain component A; (2) adding 1-2 parts by weight of deionized water, the component A and 5-6 parts by weight of an amino coupling agent to 120 parts by weight of ethyl acetate, stirring and mixing at 70-75° C. for 12-14 hours, filtering, taking the filter residue, washing it with deionized water, and finally vacuum drying it at 60-80° C. until constant weight, to obtain component B; (3) adding 1 part by weight of styrene, 0.5-1 part by weight of glycidyl methacrylate and 3-4 parts by weight of methyl acrylate to 120 parts by weight of N,N-dimethylformamide, and then adding dropwise 13-15 parts by weight of azobisisobutyronitrile solution at 60-70° C. with stirring. After all the addition is completed, continue stirring at a constant temperature for 8-10 hours to obtain component C; (4) Adding component B to component C, stirring at 70-75° C. for 4-6 hours, filtering, taking the filter residue, washing with deionized water, and finally vacuum drying at 60-80° C. until constant weight, the preparation is completed.

3. The method for preparing a TPU film containing carbon nanotubes according to claim 2, characterized in that: The deep eutectic solvent in step (1) is prepared by the following steps: Zinc chloride and lactic acid are mixed at a molar ratio of 1:7-10 at 80-90°C for 12 hours with stirring, and the mixture is naturally cooled to room temperature to complete the preparation.

4. The method for preparing a TPU film containing carbon nanotubes according to claim 2, characterized in that: The amino coupling agent in step (2) is 3-aminopropyltrimethoxysilane.

5. The method for preparing a TPU film containing carbon nanotubes according to claim 2, characterized in that: The azobisisobutyronitrile solution in step (3) is prepared by the following steps: Azobisisobutyronitrile and N,N-dimethylformamide are mixed at a mass ratio of 1:30-40 and stirred for 10-15 minutes at room temperature to complete the preparation.

6. The method for preparing a TPU film containing carbon nanotubes according to claim 1, characterized in that: In step A, the thickness of the first film layer is 60-65 μm.

7. The method for preparing a TPU film containing carbon nanotubes according to claim 1, characterized in that: The drying in step C refers to drying at 85-90° C. for 40 min.

8. A TPU film containing carbon nanotubes prepared by the preparation method according to any one of claims 1 to 7.

9. The TPU film containing carbon nanotubes according to claim 8, characterized in that: The thickness of the TPU film containing carbon nanotubes is 90-100 μm.

10. An application of a TPU film containing carbon nanotubes prepared by the preparation method according to any one of claims 1 to 7, characterized in that: The TPU film containing carbon nanotubes is used in thermal insulation products.