CN118306081A - Efficient radiation cooling film with excellent weather resistance and preparation method thereof - Google Patents

Abstract

The invention discloses a high-efficiency radiation cooling film with excellent weather resistance and a preparation method thereof. In the light reflection layer of the radiation cooling film, a polymer material matrix has a multi-layer structure overlapping along the normal direction, a filler is evenly distributed between the layer structures, and the polymer material matrix also has a microporous structure, and the microporous structure and the filler cooperate to reflect sunlight; in the atmospheric window emission layer, an ultraviolet light shielding agent is evenly dispersed in a fluoroplastic matrix. The preparation method is to first use a polyolefin polymer material, a porogen and a filler to prepare a light reflection layer by blending, extruding and extracting, and use a fluorine polymer material and an ultraviolet light shielding agent to prepare an atmospheric window emission layer by blending, extruding or salivating, and then bond the light reflection layer and the atmospheric window emission layer by a glue layer to form a radiation cooling film. The radiation cooling film prepared by the invention has a strong sunlight reflectivity and an atmospheric window band emissivity, and has excellent weather resistance.

Description

A high-efficiency radiation cooling film with excellent weather resistance and preparation method thereof

Technical Field

The invention relates to the technical field of polymer processing and molding, and in particular to a high-efficiency radiation cooling film with excellent weather resistance and a preparation method thereof.

Background technique

The earth's atmosphere has a transparent window in the 8-13μm band, and the light waves in this band are rarely reflected, absorbed, and scattered when passing through the atmosphere. Objects on the earth can radiate their own heat back to space in the form of thermal radiation through this transparent window and use the universe as the cold end to achieve the purpose of cooling. Radiative cooling uses this principle to achieve a cooling effect and is a zero-energy passive cooling technology. During the day, objects heat up due to solar radiation, so it is very practical to be able to achieve daytime radiative cooling, which requires that the radiative cooling film needs to have a relatively high reflectivity in the solar spectrum band and a high emissivity in the atmospheric window band. At present, studies have found that when used during the day, if the radiative cooling film absorbs 1% more sunlight, its cooling capacity will also be reduced by about 10%. Therefore, an efficient radiative cooling film not only needs to have a high infrared emissivity, but also needs to have excellent sunlight reflection ability.

There are many ways to achieve high reflectivity in the solar spectrum band and high emissivity in the atmospheric window band. In recent years, the radiation cooling materials that have been studied more are mainly metamaterial coatings, polymer materials, and multilayer films. Commonly used polymer materials have simple structures, easy to obtain raw materials, cheap prices, and are easier to industrialize. In recent years, they have been used more and more in the field of radiation cooling. In 2021, Ji Zhang et al. prepared a three-layer radiation cooling film by pressing a polyester woven cloth between two layers of UHMWPE (ultra-high molecular weight polyethylene) microporous membranes through molding. The preparation process of the radiation cooling film is simple, the solar reflectivity reaches 95%, and the infrared light emissivity can reach 84%, which can make the surface temperature of the object lower than the ambient temperature by about 5°C. However, in actual applications, the UHMWPE film has problems such as poor aging resistance, which makes it difficult to promote and apply the product in actual production.

In 2020, Li Zhongming's research group at Sichuan University used an electrospinning machine to prepare a three-layer composite material of PA/PVDF/PE. Among them, the C-F bond in PVDF gives the composite material an extremely high atmospheric window emissivity; the difference in refractive index between PA (polyamide), PVDF (polyvinylidene fluoride), and PE (polyethylene) brings a strong scattering effect, and the staggered arrangement of the fibers also enhances this effect. Therefore, the composite material has a reflectivity of more than 90% in the solar band; in addition, the hydrophilicity of PA and the wear resistance of PE also increase the functionality of the composite material. However, the study did not optimize the weather resistance of the product.

In summary, daytime radiation cooling film has broad application prospects, especially polymer materials have broad application prospects in this field, but current research rarely involves the comprehensive optimization of product aging resistance and solar emissivity, so the practicality of the products is not great and needs further development.

Summary of the invention

The purpose of the present invention is to overcome the shortcomings of the prior art and provide a high-efficiency radiation cooling film with excellent weather resistance. The radiation cooling film has a simple structure, a wide range of raw materials, strong solar reflectivity and atmospheric window band emissivity, and excellent weather resistance.

Another object of the present invention is to provide a method for preparing the above-mentioned efficient radiation cooling film with excellent weather resistance, which can realize large-scale efficient and continuous production of radiation cooling molds, and has high production efficiency and low production cost.

The technical solution of the present invention is: a high-efficiency radiation cooling film with excellent weather resistance, comprising a light reflection layer, a glue layer and an atmospheric window emission layer connected in sequence; wherein,

The light reflecting layer includes a polymer material matrix and a filler. The polymer material matrix has a multi-layer structure overlapping along the normal direction, and the filler is evenly distributed between the layer structures. At the same time, the polymer material matrix also has a microporous structure, and the microporous structure and the filler cooperate to reflect sunlight.

The atmospheric window emission layer includes a fluoroplastic matrix and an ultraviolet light shielding agent, and the ultraviolet light shielding agent is uniformly dispersed in the fluoroplastic matrix.

In the high-efficiency radiation cooling film, the reflectivity of sunlight in its light reflection layer can be effectively improved under the synergistic reflection effect of the filler and the microporous structure. The main reasons are as follows: (1) The particle size of the filler partially overlaps with the wavelength of sunlight, which amplifies the scattering effect when sunlight is incident; (2) The microporous structure in the polymer material matrix can, on the one hand, enhance the scattering of the corresponding light wavelength, and on the other hand, allow the light wave to be reflected multiple times after entering the radiation cooling film, further reducing the transmittance and further improving the reflectivity; (3) There is a large refractive index difference at the interface between the polymer material matrix and the filler. According to the Fresnel formula, the greater the refractive index difference before and after the light is incident, the greater the final reflectivity. In addition, the addition of fillers can play a pore-forming role, which helps to increase the porosity of the polymer material matrix, thereby improving the reflectivity of the reflection layer through the microporous structure. Its atmospheric window emission layer is composed of a polymer material with high infrared emissivity (i.e. fluoroplastic) as the matrix, which can greatly improve the atmospheric window emissivity of the radiation cooling film. At the same time, ultraviolet light shielding agent is also added to this layer to prevent the radiation cooling film from aging after absorbing ultraviolet light for a long time and affecting its performance.

In the light reflection layer, the pore size of the microporous structure in the polymer material matrix is 0.1-20 μm, and the porosity of the microporous structure is 50-90%. Tests have shown that within this pore size and porosity range, the reflectivity of the radiation cooling film can be effectively guaranteed to meet actual use requirements.

In the light reflecting layer, the main raw material of the polymer material matrix is one or more polyolefin materials, including one or more of ultra-high molecular weight polyethylene (UHMWPE), high-density polyethylene (UHMWPE) or polypropylene (PP).

In the light reflecting layer, the filler is a polymer filler with enhanced light reflecting ability, including one or more of polyvinyl fluoride particles (PVF), polyvinylidene fluoride particles (PVDF) or vinylidene fluoride-hexafluoropropylene copolymer particles (PVDF-HFP).

In the atmospheric window emission layer, the main raw material of the fluoroplastic matrix is one or more of polyvinylidene fluoride (PVDF), ethylene-tetrafluoroethylene copolymer (ETFE), fluorinated ethylene propylene copolymer (FEP) or ethylene-tetrafluoroethylene-hexafluoropropylene terpolymer (EFEP). In the selection of raw materials, not only the requirements of high infrared emissivity but also the requirements of high light transmittance are required, otherwise it will affect the function of the light reflection layer of the lower layer.

In the atmospheric window emission layer, the ultraviolet light shielding agent is titanium dioxide (TiO ₂ ) and zinc oxide (ZnO) among inorganic ultraviolet light shielding agents, or is a benzophenone type organic ultraviolet light shielding agent, a benzotriazole type organic ultraviolet light shielding agent, a triazine type organic ultraviolet light shielding agent, etc. In the selection of the ultraviolet light shielding agent, the addition amount of the ultraviolet light shielding agent is required to effectively cut off the ultraviolet light, but have little effect on the transmittance of the infrared light emission layer.

The material of the glue layer is polyacrylic resin adhesive, polyacrylic resin, polyurethane adhesive, epoxy resin adhesive, synthetic adhesive, urea-formaldehyde resin adhesive or polyvinyl acetate adhesive. In the selection of glue, it is required that the glue does not affect the transmission of light between the light reflection layer and the infrared light emission layer.

The present invention provides a method for preparing a high-efficiency radiation cooling film with excellent weather resistance, comprising the following steps:

(1) blending a polyolefin polymer material, a porogen and a filler according to a preset ratio to form a light reflecting layer mixture;

(2) extruding the light reflection layer mixture into a film to form a light reflection layer gel film with porogen and filler distributed inside;

(3) biaxially stretching the prepared light-reflecting layer gel film, so that the polymer molecular chains of the polymer material matrix in the light-reflecting layer gel film are oriented along the stretching direction to form a layered structure in which multiple matrix layers overlap and are parallel to the stretching plane, and at the same time, the polymer molecular chains will squeeze the filler and the porogen into the gaps between the matrix layers, thereby forming an alternating sandwich structure;

(4) extracting the stretched light-reflecting layer gel film to remove the porogen, thereby forming a light-reflecting layer having micropores and fillers distributed therein;

(5) blending the fluorine-containing polymer material and the ultraviolet light shielding agent according to a preset ratio to form an atmospheric window emission layer mixture;

(6) extruding or casting the atmosphere window emission layer mixture into a film to form an atmosphere window emission layer having an ultraviolet light shielding agent uniformly distributed therein;

(7) The light reflection layer and the atmosphere window emission layer are bonded together by a glue layer to form a complete high-efficiency radiation cooling film.

In the step (4), ultrasonic extraction is used during extraction, and the light reflection layer gel film is continuously passed through an ultrasonic extraction pool for extraction. The extraction liquid used in the ultrasonic extraction pool is one of water, ethanol, n-hexane, acetone or chloroform.

In the step (7), before bonding the light reflecting layer and the atmosphere window emitting layer, the film surfaces of the light reflecting layer and the atmosphere window emitting layer are first subjected to corona treatment or plasma treatment.

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

The high-efficiency radiation cooling film with excellent weather resistance is a three-layer structure with a simple structure and a wide range of raw materials. Its light reflection layer uses the synergistic reflection effect of fillers and microporous structures to have a strong visible light reflectivity. Its atmospheric window emission layer has a high emissivity and can effectively radiate heat, making the radiation cooling film have excellent cooling and temperature reduction capabilities. At the same time, the atmospheric window emission layer is the upper layer, and the ultraviolet light shielding agent is evenly distributed in it, which can greatly reduce the absorption of ultraviolet light by the radiation cooling film, thereby making the radiation cooling film have excellent weather resistance.

The high-efficiency radiation cooling film with excellent weather resistance has a stable structure. The filler in the light reflection layer is embedded and dispersed in a multilayer structure of a polymer material matrix with a microporous structure and is not easy to fall off. The light reflection layer and the atmospheric window emission layer are pretreated to increase the surface activity and then bonded with a suitable glue, so that the interface between the two layers is stably bonded.

In the preparation method of the high-efficiency radiation cooling film with excellent weather resistance, polyolefin polymer is used as the polymer matrix of the sunlight reflection layer. The material system has low cost and a wide range of material types. The preparation method is simple, easy to operate, and has high production efficiency, which is suitable for large-scale industrial production. In addition, the radiation cooling film replaces the traditional metal reflective substrate with a polymer material, which simplifies the preparation process of the film and reduces the preparation cost of the film. At the same time, due to the strong flexibility of the polymer, its application scenarios are greatly broadened, and it has a broad market space.

In the preparation method of the high-efficiency radiation cooling film with excellent weather resistance, the light reflection layer is subjected to biaxial stretching treatment to maximize the mechanical properties of the radiation cooling film, so that the final product is an ultra-thin high-strength radiation cooling film that is not easily damaged even under high tension, thereby greatly improving the performance of the product.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a schematic diagram of the cross-sectional principle of the high-efficiency radiation cooling film with excellent weather resistance.

FIG2 is a cross-sectional electron microscope image of the light reflecting layer.

In the above figures, the components indicated by the respective reference numerals are as follows: 1 is an atmospheric window emission layer, 2 is a glue layer, 3 is a light reflecting layer, 4 is a fluoroplastic matrix, 5 is an ultraviolet light shielding agent, 6 is a polymer material matrix, and 7 is a filler.

Detailed ways

The present invention will be further described in detail below in conjunction with examples, but the embodiments of the present invention are not limited thereto.

Example 1

This embodiment provides a high-efficiency radiation cooling film with excellent weather resistance.

As shown in Figure 1, the high-efficiency radiation cooling film has a light reflecting layer 3, a glue layer 2 and an atmospheric window emission layer 1 which are connected in sequence; wherein the light reflecting layer includes a polymer material matrix 6 and a filler 7, the polymer material matrix has a multi-layer structure overlapping along the normal direction, and the filler is evenly distributed between the layer structures; at the same time, the polymer material matrix also has a microporous structure, and the microporous structure and the filler cooperate to reflect sunlight; the atmospheric window emission layer includes a fluoroplastic matrix 4 and an ultraviolet light shielding agent 5, and the ultraviolet light shielding agent is evenly dispersed in the fluoroplastic matrix.

In the above-mentioned light reflecting layer, the pore size of the microporous structure in the polymer material matrix is 0.1 to 20 μm, and the porosity of the microporous structure is 50 to 90%. It has been proved through experiments that within the range of pore size and porosity, the reflectivity of the radiation cooling film can be effectively guaranteed to meet the actual use requirements. The main raw materials of the polymer material matrix are one or more polyolefin materials, including one or more of ultra-high molecular weight polyethylene (UHMWPE), high-density polyethylene (UHMWPE) or polypropylene (PP). The filler can be a polymer filler with enhanced light reflection ability, including one or more of polyvinyl fluoride particles (PVF), polyvinylidene fluoride particles (PVDF) or vinylidene fluoride-hexafluoropropylene copolymer particles (PVDF-HFP).

In the above-mentioned atmospheric window emission layer, the main raw material of the fluoroplastic matrix is one or more of polyvinylidene fluoride (PVDF), ethylene-tetrafluoroethylene copolymer (ETFE), fluorinated ethylene propylene copolymer (FEP) or ethylene-tetrafluoroethylene-hexafluoropropylene terpolymer (EFEP). In the selection of raw materials, not only the requirements of high infrared emissivity must be met, but also the requirements of high light transmittance must be met, otherwise it will affect the function of the light reflection layer of the lower layer. The ultraviolet light shielding agent adopts titanium dioxide ( _TiO2 ) and zinc oxide (ZnO) in inorganic ultraviolet light shielding agents, or adopts benzophenone organic ultraviolet light shielding agents, benzotriazole organic ultraviolet light shielding agents, triazine organic ultraviolet light shielding agents, etc. in organic ultraviolet light shielding agents. In the selection of ultraviolet light shielding agents, it is required that the amount of ultraviolet light shielding agents added can effectively cut off ultraviolet light, but have little effect on the light transmittance of the infrared light emission layer.

The material of the glue layer is polyacrylic resin adhesive, polyacrylic resin, polyurethane adhesive, epoxy resin adhesive, synthetic adhesive, urea-formaldehyde resin adhesive or polyvinyl acetate adhesive. In the selection of glue, it is required that the glue does not affect the transmission of light between the light reflection layer and the infrared light emission layer.

When the above-mentioned high-efficiency radiation cooling film is used, its principle is as follows: in its light reflection layer, under the synergistic reflection effect of the filler and the microporous structure, the reflectivity of sunlight can be effectively improved. The main reasons are as follows: (1) The particle size of the filler partially overlaps with the wavelength of sunlight, which amplifies the scattering effect when the sunlight is incident; (2) The microporous structure in the polymer material matrix can, on the one hand, enhance the scattering of the corresponding light wavelength, and on the other hand, allow the light wave to be reflected multiple times after entering the radiation cooling film, further reducing the transmittance and further improving the reflectivity; (3) There is a large refractive index difference at the interface between the polymer material matrix and the filler. According to the Fresnel formula, the greater the refractive index difference before and after the light is incident, the greater the final reflectivity. In addition, the addition of fillers can play a pore-forming role, which helps to increase the porosity of the polymer material matrix, thereby improving the reflectivity of the reflection layer through the microporous structure. Its atmospheric window emission layer is composed of a polymer material with high infrared emissivity (i.e. fluoroplastic) as the matrix, which can greatly improve the atmospheric window emissivity of the radiation cooling film. At the same time, ultraviolet light shielding agent is also added to this layer to prevent the radiation cooling film from aging after absorbing ultraviolet light for a long time and affecting its performance.

Example 2

This embodiment provides a method for preparing a high-efficiency radiation cooling film with excellent weather resistance.

In this embodiment, as a preferred solution, the weight ratio of the filler in the sunlight reflecting layer of the radiation cooling film is ≤80wt%.

The preparation method of the radiation cooling film mainly includes the following steps:

(1) The polymer material, the porogen and the filler are blended according to a preset ratio to form a light reflection layer mixture; in this embodiment, the polymer material is UHMWPE, the filler is PVDF, and the porogen is liquid paraffin. The specific operation is as follows:

(1-1) Before blending, UHMWPE and PVDF are first dried in an electric constant temperature drying oven to remove moisture from the materials to avoid problems such as polymer degradation and bubble generation caused by moisture during subsequent melt processing;

(1-2) Then, weigh a certain amount of UHMWPE, liquid paraffin and PVDF according to a preset ratio, and stir manually to pre-mix the UHMWPE powder, PVDF and liquid paraffin;

(1-3) adding the mixture of the above materials into a pulsating stretching internal mixer, setting the pulsation number to 360 times, and then taking out the material after being homogenized by the stretching flow field, thus forming a light reflecting layer mixture to be extruded;

(2) extruding the light reflection layer mixture into a film to form a light reflection layer gel film with porogen and filler distributed inside, and biaxially stretching the film at a stretching ratio of 2×2;

(3) extracting the obtained light reflection layer gel film to remove the porogen, thereby forming a sunlight reflection layer film having microporous structure and filler particles distributed inside; the specific operation process is as follows:

(3-1) clamping the wet film formed in step (2) on a bracket, immersing it in a beaker filled with n-hexane, placing the beaker in an ultrasonic cleaning machine, and starting the ultrasonic cleaning machine for extraction;

(3-2) The extracted film is dried in a vacuum oven at a temperature of about 40°C.

(4) Blending the fluorine-containing polymer material and the ultraviolet light shielding agent according to a preset ratio to form an atmospheric window emission layer mixture; in this embodiment, the fluorine-containing polymer material is PVDF, and the ultraviolet light shielding agent is a triazine ultraviolet absorber.

(5) Extruding or casting the atmospheric window emission layer mixture into a film to form an atmospheric window emission layer film with an ultraviolet light shielding agent uniformly distributed inside.

(6) Finally, the light reflection layer and the atmospheric window emission layer are bonded together with glue to form a complete radiation cooling film.

The radiation cooling film prepared by the above method has a reflective layer thickness of about 0.3mm and an emissive layer thickness of about 20um. After testing and analysis, the visible light reflectivity is 93.4%, the atmospheric window emissivity is 84.5%, and the tensile strength is 15MPa.

Example 3

This embodiment provides a method for preparing a high-efficiency radiation cooling film with excellent weather resistance. Compared with embodiment 2, the difference is that:

In this embodiment, the fluorine-containing polymer material is ETFE, and the ultraviolet light shielding agent is a compound of _TiO2 and a triazine ultraviolet absorber.

The preparation method of the radiation cooling film mainly includes the following steps:

(1) The polymer material, the porogen and the filler are blended according to a preset ratio to form a light reflection layer mixture; in this embodiment, the polymer material is UHMWPE, the polymer filler is PVDF, and the porogen is liquid paraffin. The specific operation is as follows:

(1-1) Before blending, UHMWPE and PVDF were dried in an electric constant temperature drying oven to remove moisture from the materials;

(1-2) Then, weigh a certain amount of UHMWPE, liquid paraffin and PVDF according to a preset ratio, and stir manually to pre-mix the UHMWPE powder, PVDF and liquid paraffin;

(1-3) adding the mixture of the above materials into a pulsating stretching internal mixer, setting the pulsation number to 360 times, and then taking out the material after being homogenized by the stretching flow field, thus forming a light reflecting layer mixture to be extruded;

(2) extruding the mixture into a film to form a gel film with porogen and filler distributed inside, and water cooling;

(3) biaxially stretching the obtained gel film at a stretching ratio of 2×2;

(4) extracting the stretched gel film to remove the porogen, thereby forming a sunlight reflecting layer film with microporous structure and filler particles distributed inside; the specific operation process is as follows:

(4-1) clamping the wet film formed in step (2) on a bracket, immersing it in a beaker filled with n-hexane, placing the beaker in an ultrasonic cleaning machine, and starting the ultrasonic cleaning machine for extraction;

(4-2) The extracted film is dried in a vacuum oven at a temperature of about 40°C.

(5) blending ETFE, _TiO2 and triazine ultraviolet absorber according to a preset ratio to form an atmospheric window emission layer mixture;

(6) Extruding and casting the mixture into a film to form an atmospheric window emission layer film with ultraviolet light shielding agent uniformly distributed inside.

(7) Finally, the light reflection layer and the atmospheric window emission layer are bonded together with glue to form a complete radiation cooling film.

The radiation cooling film prepared by the above method has a reflective layer thickness of about 0.3mm and an emissive layer thickness of about 20um. After testing and analysis, the visible light reflectivity is 96.1%, the atmospheric window emissivity is 78.3%, and the tensile strength is 20MPa.

As described above, the present invention can be better implemented. The above embodiments are only preferred embodiments of the present invention and are not intended to limit the scope of implementation of the present invention; that is, all equivalent changes and modifications made according to the content of the present invention are covered by the scope of protection required by the claims of the present invention.

Claims (10)

1. A high-efficiency radiation cooling film with excellent weather resistance, characterized in that it has a light reflection layer, a glue layer and an atmospheric window emission layer connected in sequence; wherein, The light reflecting layer includes a polymer material matrix and a filler. The polymer material matrix has a multi-layer structure overlapping along the normal direction, and the filler is evenly distributed between the layer structures. At the same time, the polymer material matrix also has a microporous structure, and the microporous structure and the filler cooperate to reflect sunlight. The atmospheric window emission layer includes a fluoroplastic matrix and an ultraviolet light shielding agent, and the ultraviolet light shielding agent is uniformly dispersed in the fluoroplastic matrix. 2. According to claim 1, a high-efficiency radiation cooling film with excellent weather resistance is characterized in that in the light reflecting layer, the pore size of the microporous structure in the polymer material matrix is 0.1 to 20 μm, and the porosity of the microporous structure is 50 to 90%. 3. According to claim 1, a high-efficiency radiation cooling film with excellent weather resistance is characterized in that in the light reflecting layer, the main raw material of the polymer material matrix is one or more of ultra-high molecular weight polyethylene, high-density polyethylene or polypropylene. 4. A high-efficiency radiation cooling film with excellent weather resistance according to claim 1, characterized in that in the light reflecting layer, the filler is one or more of polyvinyl fluoride particles, polyvinylidene fluoride particles or vinylidene fluoride-hexafluoropropylene copolymer particles. 5. According to claim 1, a high-efficiency radiation cooling film with excellent weather resistance is characterized in that in the atmospheric window emission layer, the main raw material of the fluoroplastic matrix is one or more of polyvinylidene fluoride, ethylene-tetrafluoroethylene copolymer, fluorinated ethylene propylene copolymer or ethylene-tetrafluoroethylene-hexafluoropropylene terpolymer. 6. A high-efficiency radiation cooling film with excellent weather resistance according to claim 1, characterized in that in the atmospheric window emission layer, the ultraviolet light shielding agent is titanium dioxide, zinc oxide, benzophenone-type organic ultraviolet light shielding agent, benzotriazole-type organic ultraviolet light shielding agent or triazine-type organic ultraviolet light shielding agent. 7. According to claim 1, a high-efficiency radiation cooling film with excellent weather resistance is characterized in that the material of the glue layer is polyacrylic resin adhesive, polyacrylic resin, polyurethane adhesive, epoxy resin adhesive, synthetic adhesive, urea-formaldehyde resin adhesive or polyvinyl acetate adhesive. 8. The method for preparing a high-efficiency radiation cooling film with excellent weather resistance according to any one of claims 1 to 7, characterized in that it comprises the following steps: (1) blending a polyolefin polymer material, a porogen and a filler according to a preset ratio to form a light reflecting layer mixture; (2) extruding the light reflection layer mixture into a film to form a light reflection layer gel film with porogen and filler distributed inside; (3) biaxially stretching the prepared light-reflecting layer gel film, so that the polymer molecular chains of the polymer material matrix in the light-reflecting layer gel film are oriented along the stretching direction to form a layered structure in which multiple matrix layers overlap and are parallel to the stretching plane, and at the same time, the polymer molecular chains will squeeze the filler and the porogen into the gaps between the matrix layers, thereby forming an alternating sandwich structure; (4) extracting the stretched light-reflecting layer gel film to remove the porogen, thereby forming a light-reflecting layer having micropores and fillers distributed therein; (5) blending the fluorine-containing polymer material and the ultraviolet light shielding agent according to a preset ratio to form an atmospheric window emission layer mixture; (6) extruding or casting the atmospheric window emission layer mixture into a film to form an atmospheric window emission layer having an ultraviolet light shielding agent uniformly distributed therein; (7) The light reflection layer and the atmosphere window emission layer are bonded together by a glue layer to form a complete high-efficiency radiation cooling film. 9. The method for preparing a high-efficiency radiation cooling film with excellent weather resistance according to claim 8, characterized in that in the step (4), ultrasonic extraction is adopted during extraction, and the light reflecting layer gel film is continuously extracted through an ultrasonic extraction tank, and the extraction liquid used in the ultrasonic extraction tank is one of water, ethanol, n-hexane, acetone or chloroform. 10. The method for preparing a high-efficiency radiation cooling film with excellent weather resistance according to claim 8, characterized in that, in the step (7), before bonding the light reflecting layer and the atmospheric window emitting layer, the film surfaces of the light reflecting layer and the atmospheric window emitting layer are first subjected to corona treatment or plasma treatment.