Photochromic TPU (thermoplastic polyurethane) film as well as preparation method and application thereof

Abstract

The invention particularly relates to a photochromic TPU film and a preparation method thereof.The photochromic TPU film comprises a thermoplastic polyurethane elastomer and a photochromic material, the photochromic material is formed by mixing doped metal ions and Nb < 5 + > according to the molar ratio of 20-120 mol%, the doped metal ions are # imgabs0 # Fe < 3 + >, # imgabs1 # or # imgabs2 #, corresponding metal salt is added into the doped metal ions, the doped metal ions are doped metal ions, the doped metal ions are doped metal ions, the doped metal ions are doped metal ions, the doped metal ions are doped metal ions, the doped metal ions are doped metal ions, the doped metal ions are doped metal ions, the doped metal ions are doped metal ions, the doped metal ions are doped metal ions, and the doped metal ions are doped metal ions. The molar ratio of the doped metal to Nb is controlled to optimize the distribution concentration of the doped metal and particles, and TPU is adopted to improve the mechanical property of the film. According to the photochromic TPU film, a metal in-situ growth technology is adopted, the preparation process is simplified, dependence of high energy consumption and complex preparation means is avoided by in-situ growth of niobium pentoxide nanoparticles doped with metal elements in TPU, the production cost is greatly reduced, and the photochromic TPU film has good large-scale production potential.

Description

Technical Field

[0001] The present invention relates to the technical field of TPU films, and particularly to a photochromic TPU film and a preparation method thereof. Background Art

[0002] In recent years, in order to achieve the goal of energy conservation and emission reduction, smart window technology has shown important application prospects in the fields of optical regulation and heat management, and has received wide attention. In smart window technology, photochromic and thermochromic materials have become the research focus due to their ability to passively regulate solar radiation. Among them, vanadium dioxide, as a typical thermochromic material, relies on its unique metal-insulator phase transition characteristics to switch from a high-transmission state to a high-reflection state near 68 °C through phase transition, thereby realizing the intelligent regulation of solar radiation. However, vanadium dioxide still has various technical bottlenecks in practical applications, including a relatively high phase transition temperature, unsatisfactory color performance (usually dark yellow), insufficient chemical stability, and difficulty in achieving a balance between transparency and solar regulation ability (ΔTsol). In addition, although perovskite-based TC materials have a high photothermal response efficiency, their poor environmental stability and insufficient ΔTsol severely limit their practical applications. In contrast, photochromic materials such as tungsten trioxide have been favored in smart window research due to their fast light response speed, good reversibility, and high-contrast optical regulation ability. However, the practical application of tungsten trioxide materials is restricted by many problems, including a decrease in transparency caused by light scattering, high preparation costs, and insufficient long-term stability. For example, tungsten trioxide-based thin films usually require expensive magnetron sputtering equipment for coating preparation, and most PC devices rely on liquid electrolytes, which will reduce the long-term use stability due to liquid leakage problems. Although encapsulating tungsten trioxide with a polymer binder can partially alleviate the stability problem, due to the large refractive index difference between tungsten trioxide and the polymer matrix, the composite film is prone to light scattering when light passes through, resulting in a decrease in transparency and an increase in haze.

[0003] Compared with tungsten trioxide and vanadium dioxide, niobium pentoxide, as a transition metal oxide with a wide bandgap, has excellent chemical stability and photochromic properties. Through doping with various metal ions (such as iron), the light response ability and electron migration efficiency of niobium pentoxide are significantly improved. However, in practical applications, it still faces problems such as easy agglomeration of nanoparticles, insufficient film transparency and mechanical flexibility. In addition, the selection of the polymer matrix is also crucial for optimizing the material properties. Although traditional PMMA (polymethyl methacrylate) has high transparency, it has deficiencies in thermal stability and durability and is difficult to meet the long-term application requirements of smart windows. In contrast, TPU (thermoplastic polyurethane elastomer) has become an ideal choice to replace traditional polymer materials due to its excellent elasticity, mechanical strength and chemical resistance. Based on this, the present invention proposes a photochromic TPU film and its preparation method. By in-situ growing highly dispersed small-sized metal element-doped niobium pentoxide nanoparticles in TPU, a fully flexible photochromic film with high transparency, excellent mechanical properties and sunlight self-control ability is prepared, providing an efficient and feasible solution for smart windows and other optical regulation fields. Summary of the Invention

[0004] The purpose of the present invention is to provide a photochromic TPU film, its preparation method and application to solve the above-mentioned deficiencies of the prior art.

[0005] The purpose of the present invention is achieved through the following technical solutions: The present invention provides a photochromic TPU film, which includes a thermoplastic polyurethane elastomer and a photochromic material; the photochromic material is composed of a doped metal ion and Nb 5+ mixed 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 the present invention, by adding corresponding metal salts (such as Cr 3+ , Mn2 + , Fe 3+ , Co2 + , Ni 2+ , Cu2 + or Zn2 + ), the doped metal (Cr 3+ , Mn2 + , Fe 3+ , Co2 + , Ni 2+ , Cu2+ or Zn2 + ) The molar ratio of () to Nb is 20 - 120 mol%, to optimize the doped metal and the particle distribution concentration, and TPU (thermoplastic polyurethane) with excellent elasticity, mechanical strength and chemical resistance is used to improve the photochromic performance and mechanical properties of the film, ensuring that the film has a high solar transmittance regulation ability (ΔTsol), and can achieve efficient intelligent regulation under different light conditions, and a fully flexible photochromic film with high transparency, excellent mechanical properties and sunlight self-control ability is prepared.

[0007] Further, the photochromic material is composed of doped metal ions and Nb 5+ mixed in a molar ratio of 20 mol%, 40 mol%, 60 mol%, 80 mol%, 100 mol% or 120 mol%.

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

[0009] The present invention also provides a preparation method of a photochromic TPU film, comprising the following steps:

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

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

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

[0013] S4. Use a coating device with a gap of 200 - 300 μm to coat the precursor solution on a glass substrate. After coating, place the substrate on a hot plate at 70 - 80 °C and heat for 20 - 30 minutes to evaporate the solvent. Finally, peel the dried coating from the glass substrate to obtain a photochromic TPU film.

[0014] The present invention simplifies the preparation process by using in-situ metal growth technology. By in-situ growing niobium pentoxide nanoparticles doped with highly dispersed small-sized metal elements in TPU, a fully flexible photochromic film with high transparency, excellent mechanical properties, and sunlight self-control ability is prepared, avoiding the dependence on high energy consumption and complex preparation methods (such as hydrothermal synthesis and ball milling), greatly reducing the production cost, and having good potential for large-scale production.

[0015] Further, in step S1, the addition amount of the niobium salt solution is 0.6 - 1 g, and the niobium salt solution is niobium pentachloride.

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

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

[0018] Further, 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.

[0019] The present invention also provides an application of the photochromic TPU film, and the photochromic TPU film is applied to solar heat and daylight control.

[0020] Specifically, the photochromic TPU film is widely applicable to fields such as building intelligent windows, automotive windows, and optical display devices. In the building field, the film can be used as an intelligent window coating to achieve intelligent control of indoor lighting and temperature by adjusting light, reducing energy consumption; in the automotive industry, it can be used for window materials to achieve sunshading, temperature reduction, and privacy protection, improving driving and riding comfort; in optical display devices, it can be used to adjust optical properties, providing support for intelligent and energy-saving display technologies.

[0021] The beneficial effects of the present invention are as follows: The photochromic TPU film of the present invention controls the molar ratio of the doped metal to Nb by adding corresponding metal salts to optimize the doped metal and particle distribution concentration, and uses TPU with excellent elasticity, mechanical strength, and chemical resistance, improving the photochromic performance and mechanical properties of the film, ensuring that the film has a high solar transmittance regulation ability, and being able to achieve efficient intelligent regulation under different lighting conditions, preparing a fully flexible photochromic film with high transparency, excellent mechanical properties, and sunlight self-control ability; and the photochromic TPU film of the present invention can be applied to fields related to solar heat and daylight control, with a wide range of applications.

[0022] The preparation method of the photochromic TPU film of the present invention is simple in operation, convenient to control, high in production efficiency and low in production cost. By in-situ growing highly dispersed small-sized niobium pentoxide nanoparticles doped with metal elements in TPU, a fully flexible photochromic film with high transparency, excellent mechanical properties and sunlight self-control ability is prepared, avoiding the dependence on high energy consumption and complex preparation means, greatly reducing the production cost, and having good potential for large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a color change diagram of the photochromic TPU film of the present invention with the increase of illumination time;

[0024] Figure 2 It is a color change diagram of the photochromic TPU film after color change of the present invention without illumination. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0025] For the convenience of understanding by those skilled in the art, the present invention will be further described below in conjunction with embodiments. The content mentioned in the embodiments does not limit the present invention.

[0026] Embodiment 1

[0027] A photochromic TPU film, comprising a thermoplastic polyurethane elastomer and a photochromic material; the photochromic material is mixed in a molar ratio of 40 mol% by doping metal ions and Nb 5+ Among them, the doped metal ions are Cr 3+ , Mn 2+ , Fe 3+ , Co 2+ , Ni 2+ , Cu 2+ or Zn 2+ .

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

[0029] Further, the photochromic TPU film is applied to solar heat and daylight control. Specifically, the photochromic TPU film is suitable for fields such as building intelligent windows, automotive windows, and optical display devices.

[0030] Embodiment 2

[0031] A preparation method of a photochromic TPU film, comprising the following steps:

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

[0033] S2. At 60 °C, dissolve the thermoplastic polyurethane elastomer in 8 mL of N-methylpyrrolidone. After cooling to room temperature, transfer it to 8 mL of dichloroethane and stir for 9 hours to obtain Solution B.

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

[0035] S4. Use a coating device with a gap of 300 μm to coat the precursor solution on a glass substrate. After coating, place the substrate on a hot plate at 75 °C and heat for 25 minutes to evaporate the solvent. Finally, peel the dried coating from the glass substrate to obtain a photochromic TPU film.

[0036] Further, in Step S1, the niobium salt solution is niobium pentachloride, and the addition amount of the niobium salt solution is 0.8 g.

[0037] Further, in Step S1, the doped metal salt is CrCl3.

[0038] Further, in Step S2, the addition amount of the thermoplastic polyurethane elastomer is 4 g.

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

[0040] Further, in Step S4, during the coating process, the moving speed of the coating device is 150 mm / s, and the temperature of the glass substrate is 75 °C.

[0041] Further, in Step S4, the thickness of the prepared photochromic TPU film is 50 μm.

[0042] Example 3

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

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

[0045] S2. At 60 °C, dissolve the thermoplastic polyurethane elastomer in 8 mL of N-methylpyrrolidone. After cooling to room temperature, transfer it to 8 mL of dichloroethane and stir for 9 hours to obtain Solution B.

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

[0047] S4. Use a coating device with a gap of 300 μm to coat the precursor solution on a glass substrate. After coating, place the substrate on a hot plate at 75 °C and heat for 25 minutes to evaporate the solvent. Finally, peel the dried coating from the glass substrate to obtain a photochromic TPU film.

[0048] Further, in step S1, the niobium salt solution is niobium pentachloride, and the addition amount of the niobium salt solution is 0.8 g.

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

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

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

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

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

[0054] Example 4

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

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

[0057] S2. At 60 °C, dissolve the thermoplastic polyurethane elastomer in 8 mL of N-methylpyrrolidone, cool to room temperature, and then transfer it to 8 mL of dichloroethane and stir for 9 hours to obtain solution B;

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

[0059] S4. Use a coating device with a gap of 300 μm to coat the precursor solution on the glass substrate. After coating, place the substrate on a hot plate at 75 °C and heat for 25 minutes to evaporate the solvent. Finally, peel the dried coating from the glass substrate to obtain the photochromic TPU film.

[0060] Further, in step S1, the niobium salt solution is niobium pentachloride, and the addition amount of the niobium salt solution is 0.8 g.

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

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

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

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

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

[0066] Performance Test

[0067] Irradiate the photochromic TPU film prepared in Example 3 with an ultraviolet lamp with an intensity of 100 mW / cm 2 for a period of time, observe its color change and fading after stopping illumination. The test results are as Figure 1-2 shown.

[0068] Figure 1 This is the color change diagram of the photochromic TPU film of the present invention with the increase of illumination time. It can be seen from Figure 1 that as the irradiation time of the ultraviolet lamp increases, the photochromic TPU film gradually switches from a high light transmittance state to a light color state. When the irradiation time is 30 minutes, the photochromic TPU film reaches a dark color state, and the transmittance decreases significantly with the increase of the ultraviolet lamp irradiation time, having a high solar transmittance regulation ability. It can be seen that the photochromic TPU film of the present invention has an obvious shading and heat insulation effect.

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

[0070] The above specific embodiments further illustrate the technical solutions and beneficial effects of the present invention, rather than limiting the implementation manners. For those skilled in the art, any obvious substitution without departing from the concept of the present invention is within the protection scope of the present invention.

Claims

1. A photochromic TPU film, characterized in that: The invention comprises a thermoplastic polyurethane elastomer and a photochromic material; the photochromic material is doped with metal ions and Nb 5+ The mixture 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 + .

2. The photochromic TPU film according to claim 1, characterized in that: The photochromic material is doped with metal ions and Nb 5+ The mixture is prepared by mixing at a molar ratio of 20 mol%, 40 mol%, 60 mol%, 80 mol%, 100 mol% or 120 mol%.

3. The photochromic TPU film according to claim 1, characterized in that: The thickness of the photochromic TPU film is 40-60 μm.

4. The method for preparing the photochromic TPU film according to any one of claims 1 to 2, characterized in that: The steps include: S1. Dissolve the niobium salt solution in 3-5 mL of N-methylpyrrolidone, then add the corresponding doping metal salt to make the doping metal ions and Nb 5+ The molar ratio is 20-120 mol%, and stirred at room temperature for 2-5 hours to obtain solution A; S2. Dissolve the thermoplastic polyurethane elastomer in 6-10 mL N-methylpyrrolidone at 50-70° C., cool to room temperature, and then transfer to 6-10 mL dichloroethane and stir for 8-10 hours to obtain solution B; S3. At room temperature, mix solution A and solution B in a volume ratio of 1:3-5, and stir for 1-3 hours to obtain a precursor solution; S4. Use a coating device with a gap of 200-300 μm to coat the precursor solution on a glass substrate. After coating, place the substrate on a hot plate at 70-80° C. and heat for 20-30 minutes to evaporate the solvent. Finally, peel off the dried coating from the glass substrate to obtain a photochromic TPU film.

5. The method for preparing a photochromic TPU film according to claim 4, characterized in that: In step S1, the niobium salt solution is added in an amount of 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 dissolved into niobium pentachloride.

7. The method for preparing a photochromic TPU film according to claim 4, characterized in that: In step S1, the doping 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 thermoplastic polyurethane elastomer is added in an amount of 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 coating device moves at a speed of 100-200 mm / s and the temperature of the glass substrate is 70-80°C.

10. The use of the 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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