Preparation method of thermochromic leather composite material based on waste textiles

Abstract

The present invention discloses a method for preparing a thermochromic leather composite material based on waste textiles. First, waste carbon fiber and waste polyester fiber are used as raw materials, and carbon fiber needle felt and polyester non-woven fabric are respectively produced through a needle-punching process. Then, the carbon fiber needle felt and polyester non-woven fabric are alternately laid and reinforced with needle punching to produce a preform with both the upper and lower surface layers of polyester non-woven fabric. The preform is then immersed in a thermoplastic polyurethane solution so that the interior and surface of the preform are filled with the thermoplastic polyurethane solution, and then removed and dried to evaporate the solvent. Thermochromic ink is then printed on the surface of the dried preform, and thermoplastic polyurethane films are laid on both the upper and lower surfaces of the preform, followed by hot pressing and curing to produce the thermochromic leather composite material. The present invention uses waste carbon fiber and polyester fiber as reinforcing materials and thermoplastic polyurethane as the matrix material to produce a leather composite material with high softness, excellent electrical and heat transfer properties, and mechanical properties.

Description

Technical Field

[0001] The invention relates to the field of composite materials, in particular to a method for preparing a thermochromic leather composite material based on waste textiles. Background Art

[0002] The amount of waste textiles continues to increase, and the recycling of waste textiles is particularly important. Most of the waste carbon fibers are in the form of chopped carbon fibers or discarded composite materials. The source of waste chopped carbon fibers is mainly the manufacturing process of composite materials, such as waste and scraps generated in the weaving, weaving and non-woven processes of carbon fibers, which account for a large part (up to 40%) of the entire waste carbon fiber recycling. Traditional methods of recycling waste carbon fibers include two physical treatment methods: landfill and incineration, which have a great impact on the environment and cause serious waste of resources.

[0003] Fiber-reinforced composites are widely used in many fields due to their high specific strength, large specific modulus, good corrosion resistance, strong designability, and excellent durability. For example, they have significant development advantages in the process application of various aerospace and automotive components, such as seat cushions. Therefore, recycling waste carbon fiber for the preparation of fiber-reinforced composites, especially for automotive interiors or parts, not only reduces resource waste but also alleviates market demand for carbon fiber, and is an area of ​​urgent research. Summary of the Invention

[0004] In view of the deficiencies in the prior art, the technical problem to be solved by the present invention is to provide a method for preparing a thermochromic leather composite material based on waste textiles.

[0005] The technical solution of the present invention to solve the technical problem is to provide a method for preparing a thermochromic leather composite material based on waste textiles, characterized in that the method comprises the following steps:

[0006] Step 1: Using waste carbon fiber and waste polyester fiber as raw materials, a carbon fiber needle felt and a polyester non-woven fabric are respectively produced by a needle punching process; then, using the carbon fiber needle felt and the polyester non-woven fabric as raw materials, the carbon fiber needle felt and the polyester non-woven fabric are first laid in an alternating manner, and then the whole is needle-punched and reinforced to produce a composite material preform with both the upper and lower surface layers being polyester non-woven fabrics;

[0007] Step 2: Immersing the preform from step 1 in a thermoplastic polyurethane solution so that the interior and surface of the preform are filled with the thermoplastic polyurethane solution, thereby obtaining an impregnated preform; then removing the impregnated preform and drying the solvent until the mass of the impregnated preform no longer changes, thereby obtaining a dried preform;

[0008] Step 3: Print the thermochromic ink on the surface of the dried preform by 3D printing; then lay a thermoplastic polyurethane film on the upper and lower surfaces of the printed preform, and hot-press and cure it to obtain a thermochromic leather composite material.

[0009] Compared with the prior art, the present invention has the following beneficial effects:

[0010] (1) The present invention uses waste carbon fiber and waste polyester fiber as reinforcing materials and thermoplastic polyurethane as the matrix material. It utilizes a needle punching process and a hot pressing process to give full play to the excellent properties of different reinforcing fibers to produce a leather composite material with high softness, excellent electrical and thermal conductivity and mechanical properties. The leather composite material is more suitable for car heated seat cushions, desktop heating pads, etc.

[0011] (2) The waste carbon fibers and waste polyester fibers of the present invention are derived from waste textiles and waste scraps, which fully utilize waste resources, reduce resource waste, greatly reduce costs, and are beneficial to achieving high-value utilization of waste textiles.

[0012] (3) The present invention adds carbon fiber to give the leather composite material its corresponding characteristics. On the one hand, the lightweight characteristics of carbon fiber are used to prepare automobile interiors or parts, which can effectively reduce the weight of the car body and make the car develop in the direction of lightweight. On the one hand, carbon fiber has high strength and elastic modulus. It can resist strain locally in the surrounding matrix, so that more stress is concentrated on the carbon fiber, thereby playing a reinforcing role. On the other hand, carbon fiber has high conductivity: the surface of the leather composite material is printed with thermochromic ink at different temperatures. By utilizing the conductivity of carbon fiber, after the leather composite material is energized, the pattern is made to show different colors at different temperatures by electric heating. When it is made into products such as heating pads, the composite material is heated or otherwise changed in temperature under power, showing the corresponding color of the pattern at that temperature. The temperature of the product can be judged by observing the color of the pattern.

[0013] (4) The present invention adopts three-dimensional needle punching technology to prepare preforms. After needling, needle-punched fibers are continuously introduced into the original multi-layer two-dimensional fiber fabric to achieve the dispersion, rearrangement and fixation of the fiber layers, thereby making the preforms of better quality and better bonding performance, effectively improving the interlayer performance of the leather composite material, improving the interface bonding performance, and reducing the delamination phenomenon.

[0014] (5) The addition of polyester fiber can make the leather composite material highly similar to genuine leather in texture and appearance, and at the same time perform well in terms of waterproofness, anti-fouling, and UV resistance.

[0015] (6) Thermoplastic polyurethane elastomer is used as the matrix material, and the wear resistance and superelastic properties of thermoplastic polyurethane elastomer are fully utilized to improve the performance of leather composite materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a side super-depth-of-field electron microscope image of the carded carbon fiber web of Comparative Example 1 of the present invention;

[0017] Figure 2 This is an ultra-depth-of-field electron microscope image of the thermochromic leather composite material at tensile fracture prepared in Comparative Example 1 of the present invention;

[0018] Figure 3 This is a side super-depth-of-field electron microscope image of the carbon fiber needle-punched felt of Example 1 of the present invention;

[0019] Figure 4 This is an ultra-depth-of-field electron microscopy image of the tensile fracture of the thermochromic leather composite material prepared in Example 1 of the present invention;

[0020] Figure 5 This is a bar graph showing the tensile strength of the thermochromic leather composite material prepared in Examples 1 to 3 of the present invention;

[0021] Figure 6 This is a bar graph of the elongation at break of the thermochromic leather composite materials prepared in Examples 1 to 3 of the present invention;

[0022] Figure 7 This is a bar graph showing the tensile strength of the thermochromic leather composite materials prepared in Examples 4 to 6 of the present invention;

[0023] Figure 8 This is a bar graph of the elongation at break of the thermochromic leather composite materials prepared in Examples 4 to 6 of the present invention;

[0024] Figure 9 This is a diagram showing the conductive and heat transfer temperature distribution of the thermochromic leather composite material prepared in Example 6 of the present invention;

[0025] Figure 10 This is a graph showing the color change of the thermochromic leather composite material prepared in Example 6 of the present invention as the temperature changes. DETAILED DESCRIPTION

[0026] The specific embodiments of the present invention are given below. The specific embodiments are only used to further illustrate the present invention and do not limit the scope of protection of the claims of the present invention.

[0027] The present invention provides a method for preparing a thermochromic leather composite material based on waste textiles (hereinafter referred to as the method), characterized in that the method comprises the following steps:

[0028] Step 1: Using waste carbon fiber and waste polyester fiber as raw materials, a carbon fiber needle felt and a polyester non-woven fabric are respectively produced by a needle punching process; then, using the carbon fiber needle felt and the polyester non-woven fabric as raw materials, the carbon fiber needle felt and the polyester non-woven fabric are first laid in an alternating manner, and then the whole is needle-punched and reinforced to produce a composite material preform (hereinafter referred to as a preform) with the upper and lower surface layers being both polyester non-woven fabrics;

[0029] Preferably, in step 1, the needling process is: opening, carding, laying and needling reinforcement in sequence; the needling reinforcement is carried out in sequence through pre-needling and main needling;

[0030] The preparation of carbon fiber needle-punched felt and polyester non-woven fabric is specifically as follows: first, waste chopped carbon fiber and waste polyester fiber are opened separately; then the opened fibers are combed separately so that the combed single fibers are interlaced with each other, and the combing process is completed to form a carbon fiber web and a polyester fiber web respectively; then the fiber webs are stacked separately in a cross-laying manner, and then respectively sent to a needle loom for pre-needling and main needling to make carbon fiber needle-punched felt and polyester non-woven fabric respectively.

[0031] Preferably, in step 1, the needle punching process is: the needle punching density is 8 to 60 needles / cm 2 The pre-needling depth is 11-16 mm, and the main needling depth is 6-9 mm.

[0032] Preferably, in step 1, the weight of the polyester nonwoven fabric is 30 to 120 g / m 2 (Preferably 30 to 80 g / m 2 , more preferably 40g / m 2 ); in the thermochromic leather composite material, the carbon fiber volume content (fiber volume content, i.e., the percentage of the volume of the fiber in the fiber-reinforced composite material to the volume of the composite material) is 4 to 25% (preferably 6 to 12%).

[0033] Step 2: Immersing the preform from step 1 in a thermoplastic polyurethane solution so that the interior and surface of the preform are filled with the thermoplastic polyurethane solution, thereby obtaining an impregnated preform; then removing the impregnated preform and drying the solvent until the mass of the impregnated preform no longer changes, thereby obtaining a dried preform;

[0034] Preferably, in step 2, the impregnation process is: the impregnation temperature is room temperature, and the impregnation time is 10 to 30 minutes (preferably 20 to 30 minutes).

[0035] Preferably, in step 2, the mass fraction of the thermoplastic polyurethane solution is 8 to 14 wt%.

[0036] Preferably, in step 2, the preparation of the thermoplastic polyurethane solution is: dissolving the TPU elastomer in a solvent and degassing to obtain the thermoplastic polyurethane solution;

[0037] The dissolution process is as follows: adding the TPU elastomer to a solvent, stirring at a temperature of 50 to 80° C. and a speed of 100 to 400 r / min for 2.5 to 5 hours to completely dissolve the elastomer; the solvent is DMF, acetone, cyclohexanone, butanone, toluene, ethyl acetate or tetrahydrofuran;

[0038] The degassing process is: degassing in a vacuum oven at a temperature of 15 to 35° C. for 15 to 40 minutes (preferably 20 to 30 minutes).

[0039] Preferably, in step 2, the drying process is: placing the preform in an environment with a temperature of 50 to 90° C. (preferably 60 to 80° C.) for 3 to 12 hours to volatilize the solvent until the quality of the preform after impregnation no longer changes.

[0040] Step 3: Print the thermochromic ink on the surface of the dried preform by 3D printing; then, after laying thermoplastic polyurethane film on the upper and lower surfaces of the printed preform, place it in a mold and hot-press and cure it to obtain a thermochromic leather composite material (referred to as leather composite material).

[0041] Preferably, in step 3, the 3D printing process is: placing the dried preform on a substrate (i.e., a print bed or a build platform of a 3D printing instrument), adding thermochromic ink into a nozzle of the 3D printing instrument, and printing an arbitrary pattern on the surface of the dried preform;

[0042] Preferably, in step 3, the 3D printing process parameters are: printing speed of 10 to 60 mm / s, printing height of 0.5 to 3 mm, number of printing layers of 1 to 8 layers, nozzle temperature of room temperature, and substrate temperature of 30 to 80°C.

[0043] Preferably, in step 3, the preparation process of the thermoplastic polyurethane film is as follows: slowly pouring the thermoplastic polyurethane solution of step 2 onto release paper or into a mold that is easy to peel off, then using a scraper to evenly apply the thermoplastic polyurethane solution, then drying to fully volatilize the solvent, and forming the thermoplastic polyurethane film;

[0044] The drying process is: drying in an environment of 50-90° C. (preferably 60-80° C.) for 20-80 minutes (preferably 40-50 minutes).

[0045] Preferably, in step 3, the hot pressing curing process is: carried out in a hot press, the hot pressing pressure is 3 to 10 MPa (preferably 5 to 7 MPa), the hot pressing temperature is 100 to 200°C (preferably 140 to 165°C), and the hot pressing time is 10 to 45 minutes (preferably 25 to 40 minutes).

[0046] Performance Testing: The thermochromic leather composite material was cut into a dumbbell shape according to the test standard and subjected to tensile testing. The thermal conductivity of the leather composite material was tested using a TC3000E thermal conductivity meter. The heat transfer performance of the leather composite material was tested by connecting it to positive and negative electrodes and applying electricity, and then photographing it with an infrared thermal imager.

[0047] Example 1

[0048] (1) Using waste carbon fiber and waste polyester fiber as raw materials, carbon fiber needle felt and polyester non-woven fabric are respectively made by needle punching process; then using carbon fiber needle felt and polyester non-woven fabric as raw materials, carbon fiber needle felt and polyester non-woven fabric are laid in an alternating manner to form a three-layer structure of polyester non-woven fabric-carbon fiber needle felt-polyester non-woven fabric, and then the whole is needle-punched to reinforce it to make a three-layer composite material preform with the upper and lower surface layers being polyester non-woven fabric and the middle layer being carbon fiber needle felt;

[0049] The acupuncture density is 15 needles / cm 2 The pre-needling depth is 11mm, the main needling depth is 9mm, the carbon fiber volume content is 12%, and the weight of the polyester non-woven fabric is 40g / m 2 ;

[0050] (2) adding TPU elastomer to DMF, stirring at 60°C and 200 r / min for 3 h, taking out and degassing in a vacuum oven at 25°C for 30 min to obtain a 12 wt% thermoplastic polyurethane solution; at room temperature, immersing the preform in the thermoplastic polyurethane solution for 20 min so that the interior and surface of the preform are filled with the thermoplastic polyurethane solution to obtain an impregnated preform; then taking out the impregnated preform and placing it in a 60°C environment for 8 h to completely volatilize the DMF to obtain a dried preform;

[0051] (3) The dried preform is placed on a substrate, and thermochromic ink is added to the nozzle of a 3D printing instrument. The thermochromic ink is printed on the surface of the dried preform by 3D printing technology. The printing speed is 40 mm / s, the printing height is 1 mm, the number of printing layers is 2, the nozzle temperature is room temperature, and the temperature of the substrate is 50°C. Then, thermoplastic polyurethane film is laid on the upper and lower surfaces of the printed preform and placed in a mold. The whole is then placed in a hot press with a hot pressing pressure of 6 MPa and hot pressing at 140°C for 25 minutes to cure and form a thermochromic leather composite material.

[0052] The preparation process of the thermoplastic polyurethane film is as follows: slowly pouring the thermoplastic polyurethane solution of step (2) onto release paper or into a mold that is easy to peel off, then using a scraper to evenly apply the thermoplastic polyurethane solution, then drying it in an environment of 60°C for 60 minutes to fully volatilize the solvent, and forming the thermoplastic polyurethane film;

[0053] Comparative Example 1

[0054] Comparative Example 1 is identical to Example 1, except that in step (1), a carded carbon fiber web (i.e., not laid and needle-punched) and a polyester nonwoven fabric are used as raw materials to lay the web to form a three-layer structure of polyester nonwoven fabric-carbon fiber web-polyester nonwoven fabric. That is, the carded carbon fiber web is used as the middle layer, and needle-punched reinforcement is not performed on the entire fabric after laying.

[0055] Comparing the test results of Example 1 and Comparative Example 1, Figure 1 and Figure 2 It can be seen that when the method of comparative example 1 is used without needle punching reinforcement, the internal fibers are less entangled, the connection between the fibers is not tight enough, the strength of the fiber web is low, and the fiber web is also relatively loose, which causes delamination in the tensile performance test of the prepared leather composite material, and also affects the tensile strength of the final leather composite material. Figure 3 and Figure 4 It can be seen that the method of Example 1 is adopted to repeatedly puncture the fiber web through needle punching technology, so that the fibers on the surface of the fiber web and the local inner layer are forced to penetrate into the interior of the fiber web, so that the fluffy carbon fiber web with the same volume content is compressed under the friction between the fibers, increasing the entanglement between the fibers, strengthening the fiber web, weakening the stratification, enhancing the interface bonding performance of the leather composite material, and improving the mechanical properties of the leather composite material.

[0056] Comparative Example 2

[0057] The difference between Comparative Example 2 and Example 1 is that in step (2), the mass fraction of the thermoplastic polyurethane solution is 20wt%. Preliminary experiments show that the leather composite material prepared using a solution with a mass fraction of 20wt% as raw material has a hard feel and poor softness.

[0058] Comparative Example 3

[0059] The difference between Comparative Example 3 and Example 1 is that in step (2), the mass fraction of the thermoplastic polyurethane solution is 18 wt %. Preliminary experiments show that the leather composite material prepared using the 18 wt % solution as raw material has a hard feel and poor softness.

[0060] Comparative Example 4

[0061] The difference between Comparative Example 4 and Example 1 is that in step (2), the mass fraction of the thermoplastic polyurethane solution is 15 wt %. Preliminary experiments show that the leather composite material prepared using the 15 wt % solution as raw material has a hard feel and poor softness.

[0062] Example 2

[0063] Example 2 is exactly the same as Example 1, except that in step (1), the volume content of carbon fiber is 9%.

[0064] Example 3

[0065] Example 3 is exactly the same as Example 1, except that in step (1), the volume content of carbon fiber is 6%.

[0066] Comparative Example 1-3 test results, by Figure 5 and Figure 6 It can be seen that, without changing the mass fraction of the thermoplastic polyurethane solution, the tensile strength and elongation at break of Example 1 are 31.29 MPa and 4.85%, respectively; the tensile strength and elongation at break of Example 2 are 28.28 MPa and 6.58%, respectively; and the tensile strength and elongation at break of Example 3 are 27.61 MPa and 9.85%, respectively. The tensile strength of Example 2 is slightly lower than that of Example 1, while the elongation at break of Example 2 changes only slightly compared to that of Example 1. The tensile strength of Example 3 is slightly lower than that of Example 1, while the elongation at break of Example 3 is higher than that of Example 1, but the elongation at break remains relatively low. Comparing the feel of the final leather composite material, the softness of Example 2 is improved compared to that of Example 1, while the softness of Example 3 is increased compared to that of Example 1. Therefore, the volume content of carbon fibers affects the softness of leather composites, and appropriately reducing the volume content of carbon fibers can improve the softness of leather composites.

[0067] Example 4

[0068] Example 4 is identical to Example 1, except that in step (2), the mass fraction of the thermoplastic polyurethane solution is 10 wt %.

[0069] Comparing the test results of Example 4 and Example 1, when the volume content of carbon fiber is 12% and the mass fraction of the thermoplastic polyurethane solution is reduced, the tensile strength and elongation at break of Example 4 are 29.73 MPa and 7.43%, respectively. The tensile strength of Example 4 is slightly lower than that of Example 1, and the elongation at break of Example 4 is slightly improved compared with that of Example 1. The leather composite material feels relatively soft.

[0070] Example 5

[0071] Example 5 is exactly the same as Example 4, except that in step (1), the volume content of carbon fiber is 9%.

[0072] Example 6

[0073] Example 6 is exactly the same as Example 4, except that in step (1), the volume content of carbon fiber is 6%.

[0074] Comparative Example 4-6 test results, by Figure 7 and Figure 8 As can be seen in Example 5, due to the reduction in carbon fiber volume content, the tensile strength of the leather composite material decreased to 27.17 MPa and the elongation at break decreased to 9.42%, both of which showed relatively small changes compared to those in Example 4. The softness of the hand also showed little change. To improve the elongation at break, the mass fraction of the thermoplastic polyurethane solution was further varied. In Example 6, due to the reduction in carbon fiber volume content, the tensile strength of the leather composite material decreased to 24.35 MPa, a slight decrease compared to Example 4. The elongation at break increased to 18.44%, more than doubling the elongation at break compared to Example 4. The softness of the composite material also improved, resulting in a softer hand. Overall, reducing the mass fraction of the thermoplastic polyurethane solution can also improve the softness of the leather composite material.

[0075] The thermal conductivity of the leather composite material of Example 6 is in the range of 0.54 to 0.56 W / (m·K).

[0076] Use infrared thermal imager to monitor the temperature change and stability of leather composite material after voltage is applied, and judge the conductive heat transfer effect and stability of leather composite material, such as Figure 9 As shown in the figure, when different voltages are applied to the sample and tested using an infrared thermal imager, the temperature distribution diagram visually reflects the sample's surface temperature, as well as the minimum and maximum temperatures in the imaged area. Figures a and b show that the sample's surface temperature changes to 34.1°C and 48.0°C when the voltage is low. Figures c and d, based on Figures a and b, increase the voltage, resulting in a gradual increase in the sample's surface temperature to 59.2°C and 76.9°C. Analysis of the temperature distribution diagrams captured by the infrared thermal imager shows that the sample's surface temperature increases with increasing voltage, demonstrating good conductive heat transfer and relatively uniform and stable heat transfer under different voltages.

[0077] The temperature of the leather composite material can be judged by the color of the pattern displayed at different temperatures of the leather composite material. Figure 10 It can be seen that when the pattern is obtained using 45°C thermochromic ink, the pattern is blue at room temperature and turns pink when the temperature is gradually raised to 45°C, indicating that the leather composite material has a good heat transfer effect.

[0078] According to the mechanical properties and softness of the final leather composite material, a preliminary experiment was carried out as shown in Table 1.

[0079] Table 1

[0080]

[0081]

[0082] Table 2

[0083]

[0084] It can be seen from Table 2 that the leather composite material prepared by the present invention can improve its interface stratification after needling, improve the interface bonding performance of the leather composite material, and the leather composite materials prepared at different carbon fiber volume contents have good heat transfer effects.

[0085] Any matters not described in the present invention are applicable to the prior art.

Claims

1. A method for preparing a thermochromic leather composite material based on waste textiles, characterized in that: The method comprises the following steps: Step 1: Using waste carbon fiber and waste polyester fiber as raw materials, a carbon fiber needle felt and a polyester non-woven fabric are respectively produced by a needle punching process; then, using the carbon fiber needle felt and the polyester non-woven fabric as raw materials, the carbon fiber needle felt and the polyester non-woven fabric are first laid in an alternating manner, and then the whole is needle-punched and reinforced to produce a composite material preform with both the upper and lower surface layers being polyester non-woven fabrics; Step 2: Immersing the preform prepared in step 1 in a thermoplastic polyurethane solution so that the interior and surface of the preform are filled with the thermoplastic polyurethane solution to obtain an impregnated preform; then removing the impregnated preform and drying the solvent until the mass of the impregnated preform no longer changes, thereby obtaining a dried preform; the mass fraction of the thermoplastic polyurethane solution is 8 to 14 wt %. Step 3: Print the thermochromic ink on the surface of the dried preform by 3D printing; then lay a thermoplastic polyurethane film on the upper and lower surfaces of the printed preform, and hot-press and cure it to obtain a thermochromic leather composite material.

2. The method for preparing a thermochromic leather composite material based on waste textiles according to claim 1, characterized in that: In step 1, the needle punching process is: the needle punching density is 8~60 needles / cm 2 The pre-needling depth is 11~16mm, and the main needling depth is 6~9mm.

3. The method for preparing a thermochromic leather composite material based on waste textiles according to claim 1, characterized in that: In step 1, the weight of polyester non-woven fabric is 30~120g / m 2 ; In the thermochromic leather composite material, the volume content of carbon fiber is 4~25%.

4. The method for preparing a thermochromic leather composite material based on waste textiles according to claim 1 or 3, characterized in that: In step 1, the weight of polyester non-woven fabric is 30~80g / m 2 ; In thermochromic leather composite materials, the volume content of carbon fiber is 6~12%.

5. The method for preparing a thermochromic leather composite material based on waste textiles according to claim 1, characterized in that: In step 2, the dipping process is: the dipping temperature is room temperature, and the dipping time is 10 to 30 minutes.

6. The method for preparing a thermochromic leather composite material based on waste textiles according to claim 1, characterized in that: In step 2, the thermoplastic polyurethane solution is prepared by dissolving the TPU elastomer in a solvent and degassing to obtain the thermoplastic polyurethane solution; The dissolution process is as follows: adding the TPU elastomer to a solvent and stirring at a temperature of 50-80°C and a speed of 100-400 r / min for 2.5-5 hours to completely dissolve it; the solvent is DMF, acetone, cyclohexanone, butanone, toluene, ethyl acetate or tetrahydrofuran; The degassing process is: degassing in a vacuum oven at a temperature of 15~35℃ for 15~40min.

7. The method for preparing a thermochromic leather composite material based on waste textiles according to claim 1, characterized in that: In step 2, the drying process is: placing in an environment with a temperature of 50-90°C for 3-12 hours.

8. The method for preparing a thermochromic leather composite material based on waste textiles according to claim 1, characterized in that: In step 3, the 3D printing process parameters are: printing speed of 10-60 mm / s, printing height of 0.5-3 mm, number of printing layers of 1-8 layers, nozzle temperature of room temperature, and substrate temperature of 30-80°C.

9. The method for preparing a thermochromic leather composite material based on waste textiles according to claim 1, characterized in that: In step 3, the preparation process of the thermoplastic polyurethane film is as follows: slowly pouring the thermoplastic polyurethane solution of step 2 onto a release paper or into a mold that is easy to peel off, then evenly applying the thermoplastic polyurethane solution by knife coating, then drying to volatilize the solvent, and forming the thermoplastic polyurethane film; The drying process is: drying in an environment of 50~90℃ for 20~80min.

10. The method for preparing a thermochromic leather composite material based on waste textiles according to claim 1, characterized in that: In step 3, the hot pressing curing process is as follows: the hot pressing pressure is 3-10 MPa, the hot pressing temperature is 100-200° C., and the hot pressing time is 10-45 min.

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