A photochromic tpu film and its preparation method and application

Abstract

The application particularly relates to a photochromic TPU film and a preparation method thereof, the photochromic TPU film comprising a thermoplastic polyurethane elastomer and a photochromic material, the photochromic material being Nb 5+ mixed at a molar ratio of 20-120 mol%, wherein the doped metal ion is Fe 3 , or by adding a corresponding metal salt, the molar ratio of the doped metal to Nb is controlled to optimize the doped metal and the particle distribution concentration, and the TPU improves the mechanical properties of the film. The photochromic TPU film of the application adopts a metal in-situ growth technology to simplify the preparation process, grows the Nb2O5 nanoparticles doped with metal elements in the TPU in-situ, avoids the dependence on high energy consumption and complex preparation methods, greatly reduces the production cost, and has good potential for large-scale production.

Description

Technical Field

[0001] This invention relates to the field of TPU film technology, specifically to a photochromic TPU film and its preparation method. Background Technology

[0002] In recent years, to achieve energy conservation and emission reduction goals, smart window technology has shown significant application prospects in the fields of optical modulation and thermal management, attracting widespread attention. Among smart window technologies, photochromic and thermochromic materials have become research focuses due to their ability to passively modulate solar radiation. Vanadium dioxide, a typical thermochromic material, relies on its unique metal-insulator phase transition characteristics to switch from a high-transmittance state to a high-reflectance state near 68℃, thereby achieving intelligent control of solar radiation. However, vanadium dioxide still faces several technical bottlenecks in practical applications, including a high phase transition temperature, undesirable color performance (usually dark yellow), insufficient chemical stability, and the difficulty in achieving a balance between transparency and solar energy modulation capability (ΔTsol). Furthermore, while perovskite-based TC materials possess high photothermal response efficiency, their poor environmental stability and insufficient ΔTsol severely limit their practical applications. In contrast, photochromic materials such as tungsten trioxide are highly favored in smart window research due to their fast photoresponse speed, good reversibility, and high-contrast optical modulation capabilities. However, the practical application of tungsten trioxide materials is constrained by several issues, including decreased transparency due to light scattering, high preparation costs, and insufficient long-term stability. For example, tungsten trioxide-based thin films typically require expensive magnetron sputtering equipment for coating preparation, and most PC devices rely on liquid electrolytes, which can reduce long-term stability due to liquid leakage. Although encapsulating tungsten trioxide with polymer binders can partially alleviate stability issues, the significant difference in refractive index between tungsten trioxide and the polymer matrix leads to light scattering in the composite film, resulting in decreased transparency and increased haze.

[0003] Compared to tungsten trioxide and vanadium dioxide, niobium pentoxide, as a wide-bandgap transition metal oxide, exhibits superior chemical stability and photochromic properties. While doping with various metal ions (such as iron) significantly enhances the photoresponse and electron mobility of niobium pentoxide, practical applications still face challenges such as nanoparticle agglomeration, insufficient film transparency, and inadequate mechanical flexibility. Furthermore, the choice of polymer matrix is ​​crucial for optimizing material performance. Traditional PMMA (polymethyl methacrylate), despite its high transparency, suffers from insufficient thermal stability and durability, making it unsuitable for the long-term application requirements of smart windows. In contrast, TPU (thermoplastic polyurethane elastomer) is an ideal alternative to traditional polymer materials due to its excellent elasticity, mechanical strength, and chemical resistance. Therefore, this invention proposes a photochromic TPU film and its preparation method. By in-situ growing highly dispersed small-sized metal-doped niobium pentoxide nanoparticles in TPU, a fully flexible photochromic film with high transparency, excellent mechanical properties, and self-controllable sunlight capabilities is prepared, providing an efficient and feasible solution for smart windows and other optical control fields. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art by providing a photochromic TPU film, its preparation method, and its application.

[0005] The objective of this invention is achieved through the following technical solution: This invention provides a photochromic TPU film, comprising a thermoplastic polyurethane elastomer and a photochromic material; the photochromic material is composed of doped metal ions and Nb. 5+ It is prepared by mixing in a molar ratio of 20-120 mol%, wherein the doped metal ion is Cr. 3+ Mn2 + Fe 3+ Co2 + Ni 2+ Cu2 + or Zn2 + .

[0006] In this invention, by adding a corresponding metal salt (such as Cr) 3+ Mn2 + Fe 3+ Co2 + Ni 2+ Cu2 + or Zn2 + ), controlling the doping of metals (Cr) 3+ Mn2 + Fe 3+ Co2 + Ni 2+ Cu2+ or Zn2 + The molar ratio of doped metal to Nb is 20-120 mol% to optimize the concentration of doped metal and particle distribution. TPU (thermoplastic polyurethane), which has excellent elasticity, mechanical strength and chemical resistance, is used to improve the photochromic performance and mechanical properties of the film. This ensures that the film has a high solar transmittance regulation capability (ΔTsol) and can achieve efficient intelligent regulation under different lighting conditions. This results in the preparation of a fully flexible photochromic film with high transparency, excellent mechanical properties and self-control of sunlight.

[0007] Furthermore, the photochromic material is composed of doped metal ions and Nb. 5+ It is prepared by mixing in molar ratios of 20 mol%, 40 mol%, 60 mol%, 80 mol%, 100 mol%, or 120 mol%.

[0008] Furthermore, the thickness of the photochromic TPU film is 40-60 μm.

[0009] This invention also provides a method for preparing a photochromic TPU film, comprising the following steps:

[0010] S1. Dissolve the niobium salt solution in 3-5 mL of N-methylpyrrolidone, then add the corresponding doped metal salt, so that the doped metal ions and Nb... 5+ The molar ratio is 20-120 mol%, and the mixture is stirred at room temperature for 2-5 hours to obtain solution A;

[0011] S2. At 50-70℃, dissolve the thermoplastic polyurethane elastomer in 6-10mL of N-methylpyrrolidone, cool to room temperature, and then transfer to 6-10mL of dichloroethane and stir for 8-10 hours to obtain solution B.

[0012] S3. At room temperature, mix solution A and solution B at a volume ratio of 1:3-5 until homogeneous, and stir for 1-3 hours to obtain the precursor solution;

[0013] S4. Using a coating device with a gap of 200-300μm, the precursor solution is coated onto a glass substrate. After coating, the substrate is placed on a hot plate at 70-80℃ and heated for 20-30 minutes to evaporate the solvent. Finally, the dried coating is peeled off from the glass substrate to obtain a photochromic TPU film.

[0014] This invention simplifies the preparation process by using in-situ metal growth technology. By growing highly dispersed small-sized niobium pentoxide nanoparticles doped with metal elements in-situ in TPU, a fully flexible photochromic film with high transparency, excellent mechanical properties and self-control of sunlight is prepared. This avoids the reliance on high energy consumption and complex preparation methods (such as hydrothermal synthesis and ball milling), significantly reduces production costs, and has good potential for large-scale production.

[0015] Furthermore, in step S1, the amount of niobium salt solution added is 0.6-1g, and the niobium salt solution is dissolved as niobium pentachloride.

[0016] Furthermore, in step S1, the doped metal salt is CrCl3, MnCl2, FeCl3, CoCl2, NiCl2, CuCl2, or ZnCl2.

[0017] Furthermore, in step S2, the amount of thermoplastic polyurethane elastomer added is 3-5g.

[0018] Furthermore, in step S4, during the coating process, the coating device moves at a speed of 100-200 mm / s, and the glass substrate temperature is 70-80°C.

[0019] The present invention also provides an application of a photochromic TPU film, wherein the photochromic TPU film is used in solar thermal and sunlight control.

[0020] Specifically, photochromic TPU films are widely used in fields such as smart windows in buildings, automotive windows, and optical display devices. In the construction industry, this film can be used as a coating for smart windows, enabling intelligent control of indoor lighting and temperature by adjusting light levels, thereby reducing energy consumption. In the automotive industry, it can be used in window materials to achieve sun shading, cooling, and privacy protection, improving driving comfort. In optical display devices, it can be used to adjust optical properties, supporting intelligent and energy-saving display technologies.

[0021] The beneficial effects of this invention are as follows: The photochromic TPU film of this invention optimizes the concentration of doped metal and particle distribution by adding appropriate metal salts and controlling the molar ratio of doped metal to Nb. Furthermore, by using TPU with excellent elasticity, mechanical strength, and chemical resistance, the photochromic performance and mechanical properties of the film are improved, ensuring that the film has a high solar transmittance control capability. It can achieve efficient intelligent control under different lighting conditions, producing a fully flexible photochromic film with high transparency, excellent mechanical properties, and self-controllable sunlight. Moreover, the photochromic TPU film of this invention can be applied to fields related to solar thermal and sunlight control, with a wide range of applications.

[0022] The method for preparing photochromic TPU film of the present invention is simple to operate, easy to control, highly efficient, and low in production cost. By growing highly dispersed small-sized niobium pentoxide nanoparticles doped with metal elements in situ in TPU, a fully flexible photochromic film with high transparency, excellent mechanical properties, and self-control over sunlight is prepared. This method avoids reliance on high energy consumption and complex preparation methods, significantly reduces production costs, and has good potential for large-scale production. Attached Figure Description

[0023] Figure 1 This is a color change diagram of the photochromic TPU film of the present invention as the light exposure time increases;

[0024] Figure 2 This is a color change diagram of the photochromic TPU film of the present invention after it has changed color and is not exposed to light. Detailed Implementation

[0025] To facilitate understanding by those skilled in the art, the present invention will be further described below with reference to embodiments. The content mentioned in the embodiments is not intended to limit the present invention.

[0026] Example 1

[0027] A photochromic TPU film includes a thermoplastic polyurethane elastomer and a photochromic material; the photochromic material is composed of doped metal ions and Nb. 5+ It is prepared by mixing at a molar ratio of 40 mol%, wherein the doped metal ion is Cr. 3+ Mn 2+ Fe 3+ Co 2+ Ni 2+ Cu 2+ or Zn 2+ .

[0028] Furthermore, the thickness of the photochromic TPU film is 50 μm.

[0029] Furthermore, the photochromic TPU film is applied to solar thermal and sunlight control. Specifically, the photochromic TPU film is suitable for applications such as smart building windows, automotive windows, and optical display devices.

[0030] Example 2

[0031] A method for preparing a photochromic TPU film includes the following steps:

[0032] S1. Dissolve the niobium salt solution in 4 mL of N-methylpyrrolidone, then add the corresponding doped metal salt, so that the doped metal ions and Nb... 5+ The molar ratio was 40 mol%, and the mixture was stirred at room temperature for 3.5 hours to obtain solution A;

[0033] S2. At 60°C, the thermoplastic polyurethane elastomer was dissolved in 8 mL of N-methylpyrrolidone. After cooling to room temperature, it was transferred to 8 mL of dichloroethane and stirred for 9 hours to obtain solution B.

[0034] S3. At room temperature, mix solution A and solution B at a volume ratio of 1:4 and stir for 1.5 hours to obtain the precursor solution.

[0035] S4. Using a coating device with a gap of 300μm, the precursor solution is coated onto a glass substrate. After coating, the substrate is placed on a hot plate at 75°C and heated for 25 minutes to evaporate the solvent. Finally, the dried coating is peeled off from the glass substrate to obtain a photochromic TPU film.

[0036] Furthermore, in step S1, the niobium salt solution is dissolved into niobium pentachloride, and the amount of niobium salt solution added is 0.8g.

[0037] Furthermore, in step S1, the doped metal salt is CrCl3.

[0038] Furthermore, in step S2, the amount of thermoplastic polyurethane elastomer added is 4g.

[0039] In this embodiment, the thermoplastic polyurethane elastomer is KRYSTALGRAN PN30.

[0040] Furthermore, in step S4, during the coating process, the coating device moves at a speed of 150 mm / s and the glass substrate temperature is 75°C.

[0041] Furthermore, in step S4, the thickness of the photochromic TPU film is 50 μm.

[0042] Example 3

[0043] A method for preparing a photochromic TPU film includes the following steps:

[0044] S1. Dissolve the niobium salt solution in 4 mL of N-methylpyrrolidone, then add the corresponding doped metal salt, so that the doped metal ions and Nb... 5+ The molar ratio was 40 mol%, and the mixture was stirred at room temperature for 3.5 hours to obtain solution A;

[0045] S2. At 60°C, the thermoplastic polyurethane elastomer was dissolved in 8 mL of N-methylpyrrolidone. After cooling to room temperature, it was transferred to 8 mL of dichloroethane and stirred for 9 hours to obtain solution B.

[0046] S3. At room temperature, mix solution A and solution B at a volume ratio of 1:4 and stir for 1.5 hours to obtain the precursor solution.

[0047] S4. Using a coating device with a gap of 300μm, the precursor solution is coated onto a glass substrate. After coating, the substrate is placed on a hot plate at 75°C and heated for 25 minutes to evaporate the solvent. Finally, the dried coating is peeled off from the glass substrate to obtain a photochromic TPU film.

[0048] Furthermore, in step S1, the niobium salt solution is dissolved into niobium pentachloride, and the amount of niobium salt solution added is 0.8g.

[0049] Furthermore, in step S1, the doped metal salt is FeCl3.

[0050] Furthermore, in step S2, the amount of thermoplastic polyurethane elastomer added is 4g.

[0051] In this embodiment, the thermoplastic polyurethane elastomer is KRYSTALGRAN PN30.

[0052] Furthermore, in step S4, during the coating process, the coating device moves at a speed of 150 mm / s and the glass substrate temperature is 75°C.

[0053] Furthermore, in step S4, the thickness of the photochromic TPU film is 50 μm.

[0054] Example 4

[0055] A method for preparing a photochromic TPU film includes the following steps:

[0056] S1. Dissolve the niobium salt solution in 4 mL of N-methylpyrrolidone, then add the corresponding doped metal salt, so that the doped metal ions and Nb... 5+ The molar ratio was 40 mol%, and the mixture was stirred at room temperature for 3.5 hours to obtain solution A;

[0057] S2. At 60°C, the thermoplastic polyurethane elastomer was dissolved in 8 mL of N-methylpyrrolidone. After cooling to room temperature, it was transferred to 8 mL of dichloroethane and stirred for 9 hours to obtain solution B.

[0058] S3. At room temperature, mix solution A and solution B at a volume ratio of 1:4 and stir for 1.5 hours to obtain the precursor solution.

[0059] S4. Using a coating device with a gap of 300μm, the precursor solution is coated onto a glass substrate. After coating, the substrate is placed on a hot plate at 75°C and heated for 25 minutes to evaporate the solvent. Finally, the dried coating is peeled off from the glass substrate to obtain a photochromic TPU film.

[0060] Furthermore, in step S1, the niobium salt solution is dissolved into niobium pentachloride, and the amount of niobium salt solution added is 0.8g.

[0061] Furthermore, in step S1, the doped metal salt is ZnCl2.

[0062] Furthermore, in step S2, the amount of thermoplastic polyurethane elastomer added is 4g.

[0063] In this embodiment, the thermoplastic polyurethane elastomer is KRYSTALGRAN PN30.

[0064] Furthermore, in step S4, during the coating process, the coating device moves at a speed of 150 mm / s and the glass substrate temperature is 75°C.

[0065] Furthermore, in step S4, the thickness of the photochromic TPU film is 50 μm.

[0066] Performance testing

[0067] The photochromic TPU film prepared in Example 3 was subjected to an intensity of 100 mW / cm. 2 Irradiate the sample with ultraviolet light for a period of time, observe the color change and fading after the light is removed, and the test results are as follows: Figure 1-2 As shown.

[0068] Figure 1 This is a color change diagram of the photochromic TPU film of the present invention as the light exposure time increases. Figure 1 As can be seen, with the increase of UV lamp irradiation time, the photochromic TPU film gradually switches from a high light transmittance state to a light color state. After irradiation time of 30 minutes, the photochromic TPU film reaches a dark color state. The transmittance decreases significantly with the increase of UV lamp irradiation time, and it has a high solar energy transmittance control capability. It can be seen that the photochromic TPU film of the present invention has obvious light-blocking and heat-insulating effects.

[0069] Figure 2 This is a color change diagram of the photochromic TPU film of the present invention after exposure to no light. Figure 2As can be seen, after the TPU film is exposed to no light, as the time without light increases, the TPU film gradually switches from a dark state to a light state, and finally returns to the high light transmittance before light exposure, that is, it completely fades. It can be seen that the photochromic TPU film of the present invention has good color change-fading repeatability.

[0070] The specific embodiments described above are further illustrations of the technical solution and beneficial effects of the present invention, and are not intended to limit the implementation methods. For those skilled in the art, any obvious substitutions without departing from the concept of the present invention are within the protection scope of the present invention.

Claims

1. A photochromic TPU film characterized in that: comprising a thermoplastic polyurethane elastomer and a photochromic material; the photochromic material is a compound doped with a metal ion and Nb 5+ mixed at a molar ratio of 20-120 mol%, wherein the doped metal ion is Cr 3+ , Mn 2+ , Fe 3+ , Co 2+ , Ni 2+ , Cu 2+ or Zn 2+ .

2. The photochromic TPU film according to claim 1, characterized in that: The photochromic material is made of a doped metal ion and Nb 5+ are mixed in a molar ratio of 20 mol%, 40 mol%, 60 mol%, 80 mol%, 100 mol% or 120 mol%.

3. The photochromic TPU film of claim 1, wherein: The photochromic TPU film has a thickness of 40-60 μm.

4. The method of claim 1-2, wherein: The method comprises the following steps: S1, dissolving the niobium salt solution in 3-5 mL of N-methylpyrrolidone, then adding the corresponding doping metal salt, so that the doping metal ion and Nb 5+ at a molar ratio of 20-120 mol%, and stirring at room temperature for 2-5 hours to obtain solution A; S2, dissolving the thermoplastic polyurethane elastomer in 6-10 mL of N-methyl pyrrolidone at 50-70 °C, and after cooling to room temperature, transferring to 6-10 mL of dichloroethane and stirring for 8-10 hours to obtain solution B; S3, mixing solution A and solution B uniformly at a volume ratio of 1:3-5 at room temperature, and stirring for 1-3 hours to obtain a precursor solution; S4, using a coating device with a gap of 200-300 μm to coat the precursor solution on a glass substrate, after coating, placing the substrate on a hot plate at 70-80 °C and heating for 20-30 minutes to evaporate the solvent, and finally peeling off the dried coating from the glass substrate to obtain a photochromic TPU film.

5. The method of claim 4, wherein the photochromic TPU film is prepared by: In step S1, the amount of niobium salt solution added is 0.6-1 g.

6. The method for preparing a photochromic TPU film according to claim 4, characterized in that: In step S1, the niobium salt solution is niobium pentachloride.

7. The method for preparing a photochromic TPU film according to claim 4, characterized in that: In step S1, the doped metal salt is CrCl3, MnCl2, FeCl3, CoCl2, NiCl2, CuCl2 or ZnCl2.

8. The method for preparing a photochromic TPU film according to claim 4, characterized in that: In step S2, the amount of thermoplastic polyurethane elastomer added is 3-5 g.

9. The method for preparing a photochromic TPU film according to claim 4, characterized in that: In step S4, during the coating process, the moving speed of the coating device is 100-200 mm / s, and the temperature of the glass substrate is 70-80 °C.

10. Use of a photochromic TPU film according to any one of claims 1 to 3, characterized in that: The photochromic TPU film is applied to solar heat and sunlight control.

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