Radiation cooling composite film and preparation method and application thereof

Abstract

The present application relates to a kind of radiation cooling composite film and its preparation method and application, belong to the technical field of radiation cooling material.The radiation cooling composite film of the present application, including micro-nano-porous elastic film and the functional coating attached to the surface of micro-nano-porous elastic film;Wherein, micro-nano-porous elastic film is obtained by the foaming of elastic film, it has micro-nano-cell structure, as the base of composite film can make composite film have the advantages of light, soft, long service life, also have the effect of passive radiation cooling.Again on the surface of micro-nano-porous elastic film there is different functional coating, including heat storage emission function layer and reflection function layer, so that the radiation cooling composite film has excellent radiation cooling effect, resistant to high and low temperature, effectively delay heat penetration etc.Characteristics, can be applied to automotive interior field, realize in-car cooling, relieve in-car temperature too high field, can be mass-produced, with the advantage of high processing efficiency.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of radiation cooling materials, in particular to a radiation cooling composite film and a preparation method and application thereof. BACKGROUND

[0002] In recent years, the number of vehicles in China has been growing continuously, and people's demand for vehicles is no longer limited to their appearance and basic performance. The personalization and functionality of vehicle interiors have also attracted market attention and pursuit. Meanwhile, the frequent occurrence of accidents such as explosions and spontaneous combustion caused by high internal temperatures of vehicles under the sun has reminded the market that the cooling function of vehicles needs to be taken seriously. The existing vehicle cooling measures mainly use car covers, sunshades or sunshading windows to block sunlight, and auxiliary devices to improve user comfort have been widely used in the automotive field and among consumers. However, such auxiliary cooling tools are generally manually installed and used, although they are simple in structure and low in price, they require additional communication from consumers and are difficult to use during vehicle travel, which has high limitations.

[0003] Therefore, it is urgent to seek more environmentally friendly and efficient cooling methods. Radiative cooling technology scatters or reflects most of the solar spectrum (0.3-2.5 μm), while taking advantage of the special spectral properties of the Earth's atmosphere, which is highly transparent to infrared radiation in the 8-13 μm atmospheric window, to exchange heat with cold space, thereby achieving passive cooling without external input. As a new type of cooling technology, radiative cooling materials come in various forms to achieve different application scenarios.

[0004] Currently, most cooling porous membranes mainly use the strategy of constructing pore structures on the membrane surface to form a rough surface to increase diffuse reflection and further improve their reflectivity to achieve cooling effects. This method has limited cooling effect and can only be effective under outdoor light, and cannot achieve all-waveband all-weather multi-environment cooling effect; at the same time, common porous membranes are often prepared by electrospinning, template method and phase separation method, which are often high in cost and difficult to achieve large-area production due to the limitations of preparation methods. SUMMARY

[0005] The present application aims to overcome the shortcomings of the prior art and provide a radiation cooling composite film and a preparation method and application thereof.

[0006] To achieve the above-mentioned purpose, the technical solution adopted by the present application is as follows:

[0007] In a first aspect, the present application provides a radiation cooling composite film, comprising a micro-nano-porous elastic film and a functional coating attached to the surface of the micro-nano-porous elastic film; wherein the functional coating comprises, from bottom to top, a heat storage and emission functional layer and a reflection functional layer; the micro-nano-porous elastic film is obtained by foaming an elastic film, and has a micro-nano-porous structure.

[0008] The radiation cooling composite film comprises a micro-nano-porous elastic film having a micro-nano-porous structure, which has the advantages of light weight, softness and long service life, and different functional coatings, including a heat storage and emission functional layer and a reflection functional layer, are attached to the surface of the micro-nano-porous elastic film, so that the radiation cooling composite film has excellent radiation cooling effect, high and low temperature resistance, and effectively delays heat penetration, can be applied to the field of automotive interiors, realizes in-vehicle cooling and relieves high temperature in the vehicle, and can be mass-produced, has high processing efficiency, and has a micro-nano-porous structure. The reflectivity of the radiation cooling composite film in the 0.3-2.5 μm band of sunlight is ≥85%, preferably ≥92%, the emissivity in the atmospheric window of 8-13 μm is ≥85%, preferably ≥92%, and the phase change enthalpy is 180.4 KJ / Kg.

[0009] Specifically, a specific elastomer is selected as a raw material for the elastic film, and it is known that different vibration modes of polymers with different molecular structures have different extinction peaks in the long-wave infrared window. When the above-mentioned elastomer is selected as a base material, the molecular vibration of the elastomer can be concentrated in the 8-13 μm band, the heat gain from sunlight can be kept to a minimum, and a large amount of infrared absorption and emission in the atmospheric window can be facilitated. At the same time, the pore size distribution of the micro-nano-porous elastic film is between 0.1-2.0 μm and far away from the mid-infrared band, so that high visible light reflectivity can be effectively achieved.

[0010] Preferably, the pore size of the micro-nano-porous elastic film is 0.3-200 μm, more preferably 0.5-150 μm, and the porosity is 50-90%, more preferably 70-95%.

[0011] Sunlight contains ultraviolet light, visible light, infrared light, etc., which are light waves with a wavelength of 0.3-2.5 μm. When light waves enter a medium, the light waves will be reflected, refracted and scattered at the interface when propagating in a non-uniform medium. Micro-nano-porous foaming forms a large number of closed pores in transparent or translucent polymers, and the micro-nano-porous foaming material appears white, and the whiteness increases with the decrease of the pore size and the increase of the porosity. When the size of the pores is comparable to the wavelength of the light waves, the pores of the micro-nano-porous polymer will cause significant scattering of sunlight, and the white micro-nano-porous polymer will exhibit diffuse reflection of sunlight. By limiting the pore size and porosity of the micro-nano-porous polymer, the micro-nano-porous polymer can exhibit good reflectivity and emissivity.

[0012] Preferably, the elastic film comprises the following raw materials by weight: 50-100 parts of the elastomer, 0-20 parts of inorganic oxide, 0-3 parts of lubricant, 0-1 part of crosslinking agent, and 0-0.5 part of antioxidant. More preferably, the elastic film comprises the following raw materials by weight: 60-80 parts of the elastomer, 10-15 parts of inorganic oxide, 1-3 parts of lubricant, 0.5-1 part of crosslinking agent, and 0.1-0.5 part of antioxidant.

[0013] The inorganic oxide is at least one of silicon dioxide, titanium dioxide, and chromium dioxide, and such inorganic oxide functional particles have high emissivity in the mid-far infrared band and high reflectivity in the near infrared band, and can further improve the cooling effect in the system.

[0014] Preferably, the elastomer comprises at least one of polyurethane thermoplastic elastomer, polyester thermoplastic elastomer, nylon elastomer, EVA crosslinked elastomer, polyolefin crosslinked elastomer, styrene crosslinked elastomer, and vulcanized rubber.

[0015] Preferably, the preparation raw material of the heat storage and emission functional layer comprises phase change microcapsules; the phase change microcapsules have a shell layer and a core layer, the shell layer comprises silicon dioxide, and the core layer comprises at least one of polyethylene glycol, paraffin, pentanetetrayl, neopentyl glycol, and trimethylol ethane; the average particle size of the phase change microcapsules is 0.1-10 μm, the phase change enthalpy is 180.4 KJ / Kg, and the emissivity is 92%.

[0016] Preferably, the preparation raw material of the reflective functional layer comprises nano functional particles; the nano functional particles comprise at least one of silicon dioxide, titanium dioxide, chromium dioxide, silicon nitride, aluminum phosphate, and aluminum oxide; and the particle size of the nano functional particles is 0.05-10 μm.

[0017] Preferably, the functional coating further comprises a waterproof functional layer, the waterproof functional layer is arranged on the surface of the reflective functional layer, the waterproof functional layer is formed by performing hydrophobic treatment on the surface of the porous layer and performing hydrophobic finishing by using a hydrophobic agent such as polytetrafluoroethylene (PTFE) hydrophobic agent, fluoride hydrophobic agent, silane hydrophobic agent, and dilute acid hydrophobic agent, which have high temperature resistance and chemical stability, so that the radiation cooling automotive interior film has the functions of waterproofing, stain prevention, and self-cleaning during use.

[0018] In a second aspect, the present application provides a preparation method of a radiation cooling composite film, comprising the following steps:

[0019] (1) performing foaming treatment on the elastic film to obtain the micro-nano-porous elastic film with micro-nano-cellular structure;

[0020] (2) heat-pressing and cooling the surface of the micro-nano-porous elastic film, and then sequentially coating the functional coating on the surface of the micro-nano-porous elastic film to obtain the radiation cooling composite film.

[0021] Preferably, in the step (1), the foaming treatment comprises the following steps: first foaming by immersing the elastic film in a supercritical fluid to obtain a specific solubility, and then second foaming by continuously heating in a drawing or molding environment to obtain a micro-nano-porous elastic film with a micro-nano-cellular structure; wherein the pressure of the first foaming is 5-40 MPa, and the temperature is 60-200°C; the supercritical fluid is CO2 fluid, N2 fluid, or a mixture of the two fluids, wherein the solubility of the supercritical fluid in the elastic body is 0.8-15 wt%.

[0022] More preferably, the hardness or modulus of the elastic body selected to have thermoplasticity and cross-linking property will affect the expansion behavior of the elastic body in the supercritical fluid micro-foaming process. Generally speaking, the foaming temperature of a plastic-elastic body with high hardness or large modulus is relatively high, while the foaming temperature of an elastic body with low hardness or small modulus is relatively low. In order to realize the micro-nano composite cell structure and different cell sizes of different layers to achieve multi-angle propagation path, two kinds of elastic bodies are selected for compounding, so as to achieve multiple diffuse reflection to improve the reflectivity and endow the passive radiation cooling function.

[0023] Preferably, the elastic film is prepared by one-step molding using multi-layer co-extrusion, including double-layer co-extrusion, three-layer co-extrusion, etc. Specifically, the steps of double-screw extrusion casting, rolling and cooling can be selected, or the steps of preparing a film, laminating the film and hot-pressing vulcanization can be selected, and more preferably the steps of the latter.

[0024] The film is prepared by open mill and double-screw extrusion casting, the time of open mill is 5-30 minutes, the temperature for preparing the film is 90-130°C; the laminating time of the film is 3-15 minutes; the temperature for hot-pressing vulcanization is 160-190°C, and the time is 5-20 minutes. The elastic film is hot-pressed before foaming, and then continuously foamed, so that the multi-layer composite film can be one-step molded without adhesive. The one-step molding by the above steps is easier to control the components in the elastic film layer, the component matching between layers and the multi-layer structure design. By limiting the component selection, preparation temperature and vulcanization temperature of each layer of the film, the cross-linking process of the elastic body can be controlled, and an integrated micro-nano-cellular structure elastic film with dense and orderly distributed structure can be prepared.

[0025] Preferably, in the step (2), the temperature of the heat-pressing is 130-160°C, and the temperature of the cooling is 4-15°C. The heat-pressing and cooling can make the micro-nano-porous elastic film with micro-nano-porous structure change in thickness, and obtain a micro-nano-porous elastic film with micro-nano-porous structure and controllable thickness size.

[0026] Preferably, in the step (2), each functional coating layer can be compounded on the surface of the micro-nano-porous elastic film by means of impregnation, padding or high-pressure spraying, etc. by using an adhesive. The adhesive is an elastic glue, including polyurethane glue, etc. The thickness of each coating layer is 0.3-1 mm, preferably 0.5-0.8 mm.

[0027] In a third aspect, the present application provides the use of the radiation cooling composite film in the preparation of automotive interiors.

[0028] Compared with the prior art, the present application has the following advantages:

[0029] (1) The radiation cooling composite film of the present application comprises a micro-nano-porous elastic film and a functional coating layer attached to the surface of the micro-nano-porous elastic film. The micro-nano-porous elastic film is obtained by foaming an elastic film, and has a micro-nano-cell structure. Using the micro-nano-porous elastic film as the base of the composite film can make the composite film have the advantages of light weight, softness and long service life. Moreover, when the composite film is irradiated by sunlight, it can cause strong Rayleigh scattering and Mie scattering, scattering sunlight into the environment, thereby greatly avoiding heat absorption, and achieving the effect of passive radiation cooling. Different functional coating layers, including a heat storage and emission functional layer and a reflection functional layer, are attached to the surface of the micro-nano-porous elastic film, so that the radiation cooling composite film has excellent radiation cooling effect, high and low temperature resistance, and can effectively delay heat penetration, and can be applied in the field of automotive interiors to achieve the fields of in-vehicle cooling and relieving high temperature in the vehicle. The radiation cooling composite film can be mass-produced, and has the advantage of high processing efficiency.

[0030] (2) The preparation method of the radiation cooling composite film of the present application is to integrally form an elastic film using an elastomer as a raw material, and then to perform foaming treatment on the elastic film to obtain a micro-nano-porous elastic film having a micro-nano-cell structure as a base layer. The micro-nano-porous elastic film can realize reflection of different wave bands of sunlight and emission of infrared waves, and can achieve good, lightweight, soft and full-waveband sunlight radiation cooling effect. Then, the surface of the micro-nano-porous elastic film is heat-pressed and cooled to be shaped, and then the functional coating layers are compounded on the surface of the micro-nano-porous elastic film in sequence to obtain the radiation cooling composite film.

[0031] (3) In the preparation method of the radiation cooling composite film of the present application, the foaming of the elastic film is to first immerse the elastomer in a supercritical fluid to perform first foaming for rapid pressure relief foaming, and then to continue to induce secondary cell nucleation by heating to obtain a micro-nano-porous elastic film having a micro-nano-cell structure with a particle size of 0.3-10 μm. The secondary foaming makes the pore size distribution of the micro-nano-porous elastic film uniform, and forms a micro-nano-cell structure. This structure can reflect different wave bands of sunlight and emit infrared waves, thereby improving the passive radiation cooling function. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 Structure diagram of the composite film of Example 1;

[0033] Figure 2 Structure diagram of the composite film of Example 3;

[0034] In the figure: 1, micro-nano-porous elastic film; 2, heat storage and emission functional layer; 3, reflection functional layer; 4, waterproof functional layer. DETAILED DESCRIPTION

[0035] In order to better illustrate the purpose, technical scheme and advantages of the present application, the present application will be further described below in combination with specific examples.

[0036] In the following examples, the experimental methods used are conventional methods unless otherwise specified, and the materials, reagents, etc. used are commercially available unless otherwise specified.

[0037] In the following examples, the materials used to prepare the radiation cooling composite film are as follows:

[0038] Thermoplastic polyurethane elastomer: TPU, HF-1385AX, Huafeng;

[0039] Thermoplastic polyester elastomer: TPEE, 1028D, BASF, Germany;

[0040] Thermoplastic nylon elastomer: PEBA, 3010, Xubang New Material Technology Co., Ltd.;

[0041] Polyolefin elastomer 1: EVA, 360, DuPont, USA;

[0042] Polyethylene elastomer 2: POE, 8150, Dow Chemical Company, USA;

[0043] Styrene elastomer: SEBS, H1053, Asahi Kasei, Japan;

[0044] Functional powder: The particle size of the phase change microcapsule is 0.1-10 μm, the size of CrO2 is 2 μm, the size of silicon nitride is 10 μm, and the size of TiO2 is 0.05 μm, commercially available;

[0045] Crosslinking agent: BIPB, commercially available;

[0046] Antioxidant: Antioxidant 1010, BASF.

[0047] Example 1

[0048] As Figure 1As shown, the radiation cooling composite membrane of Example 1 includes a microporous elastic membrane 1 and a functional coating attached to the surface of the microporous elastic membrane 1; the functional coating includes a heat storage and emission functional layer 2, a reflective functional layer 3 and a waterproof functional layer 4 from bottom to top, that is, there are a total of 3 functional coatings.

[0049] The preparation method of the radiation cooling composite membrane is as follows:

[0050] (1) The raw materials for preparing the elastic film are first mixed at 100°C, and then subjected to open milling, twin-screw extrusion casting, film stacking, and hot vulcanization to obtain an integrated multilayer elastic film; wherein, the open milling time is 20 minutes and the temperature is 100°C; the film stacking time is 10 minutes; the hot pressing vulcanization temperature is 170°C and the time is 15 minutes.

[0051] (2) The elastic membrane is immersed in a supercritical fluid to obtain a specific solubility for the first foaming. Then, the temperature is raised to 100°C and the pressure is controlled at 20MPa to induce the nucleation and growth of the foam pores, which is the second foaming, to obtain the expanded microporous elastic membrane 1.

[0052] (3) The microporous elastic membrane 1 is hot-pressed and cooled for shaping, and then a functional coating is coated on the surface of the microporous elastic membrane 1 to obtain the radiation cooling microporous elastic membrane 1. The hot-pressing temperature is 150°C, and the cooling temperature is 10°C. The heat storage and emission functional layer 2 is bonded by high-pressure spraying of polyurethane adhesive, the reflective functional layer 3 is composited by padding, and the waterproof functional layer 4 is prepared by impregnation.

[0053] The structures and preparation methods of the radiation cooling composite films in Examples 2, 4-7 and 9 are the same as those in Example 1.

[0054] Example 3

[0055] like Figure 2 As shown, the radiation cooling composite membrane of Example 3 includes a microporous elastic membrane 1 and a functional coating attached to the surface of the microporous elastic membrane 1. The functional coating includes a heat storage and emission functional layer 2 and a reflection functional layer 3 from bottom to top, that is, there are a total of 2 functional coatings.

[0056] The microporous elastic membrane 1 in each embodiment is obtained by foaming an elastic membrane; the raw materials for preparing the elastic membrane include elastomers, wherein the formulations of the composite fabrics in Examples 1 to 9 are shown in Table 1.

[0057] The preparation method of the radiation cooling composite membrane is as follows:

[0058] (1) The raw material of the elastic film is first mixed at 100℃, then opened, extruded by double screw, laminated, and heated and vulcanized to obtain an integrated multi-layer elastic film; the opening time is 20 minutes and the temperature is 100℃; the laminating time is 10 minutes; the temperature of hot pressing vulcanization is 170℃ and the time is 15 minutes.

[0059] (2) The elastic film is immersed in a supercritical fluid to obtain a specific solubility for the first foaming, then heated to 100℃ and induced to nucleate and grow under the control of pressure of 20MPa for the second foaming, to obtain an expanded micro-nano-porous elastic film 1;

[0060] (3) The micro-nano-porous elastic film 1 is hot pressed and cooled to shape, and a functional coating is coated on the surface of the micro-nano-porous elastic film 1 to obtain a radiation cooling micro-nano-porous elastic film 1. The temperature of hot pressing is 150℃ and the temperature of cooling is 10℃. The heat storage and emission functional layer 2 is bonded by high-pressure spraying of polyurethane glue, and the reflection functional layer 3 is compounded by dip coating method.

[0061] The structure and preparation method of the radiation cooling composite film of Example 8 are the same as those of Example 3.

[0062] Examples 1-9

[0063] The formulations used in each layer of the composite film of Examples 1-9 are shown in Table 1.

[0064] Table 1 (parts by weight)

[0065]

[0066]

[0067]

[0068] Comparative Example 1

[0069] The difference between Comparative Example 1 and Example 1 is that Comparative Example 1 does not contain the heat storage and emission functional layer 2.

[0070] Comparative Example 2

[0071] The difference between Comparative Example 2 and Example 1 is that Comparative Example 2 does not contain the reflection functional layer 3.

[0072] Comparative Example 3

[0073] The difference between Comparative Example 3 and Example 1 is that the heat storage and emission functional layer 2 of Comparative Example 3 is made of hollow nanometer silicon balls.

[0074] Comparative Example 4

[0075] Comparative Example 4 differs from Example 1 in that the heat-accumulating and emitting functional layer 2 of Comparative Example 4 is made of paraffin.

[0076] Comparative Example 5

[0077] Comparative Example 5 differs from Example 1 in that the step 2) of the preparation method of the radiative cooling composite film of Comparative Example 5 is not subjected to vulcanization treatment.

[0078] Comparative Example 6

[0079] Comparative Example 6 differs from Example 1 in that the step (3) of Comparative Example 6 does not perform hot pressing and cooling setting on the micro-nano-porous elastic film 1, and directly coats the functional coating on the surface of the micro-nano-porous elastic film 1.

[0080] Comparative Example 7

[0081] Comparative Example 7 differs from Example 1 in that the step 1) of obtaining the elastic film is not subjected to the step 2) of immersion in the supercritical fluid.

[0082] Performance test

[0083] The micro-nano-porous elastic film 1 of Examples 1-9 and Comparative Examples 1-7 is tested for average cell size, porosity and thickness, and the obtained radiative cooling composite film of each group is tested for solar reflectivity, and the test results are shown in Table 2, and the test methods are as follows:

[0084] Porosity: tested by drainage method, standard HG / T 2872-2009.

[0085] Average cell size: the cross section of the foamed sample is tested by SEM, and the average value of the size of more than 100 cells is counted.

[0086] Reflectivity: determined according to the LAMBDA 950 ultraviolet-visible spectrophotometer ball integration method, standard JG / T 235-2014.

[0087] Emissivity: determined according to the Nicolet iS50 Fourier transform infrared spectrometer ball integration test method, standard JG / T 235-2014.

[0088] Table 2: Performance test results of each group

[0089]

[0090]

[0091] As shown in Table 2, the micro-nano-porous elastic film 1 with micro-nano-porous structure is used as the base of the radiation cooling composite film in Examples 1-9, and the heat storage and emission functional layer 2 and the reflection functional layer 3 are respectively compounded in the micro-nano-porous elastic film 1, so that the radiation cooling composite film has a light reflectivity of 85% at most 96% in the 8-13 μm band, which indicates that the radiation cooling composite film of the present application is helpful to a large amount of infrared absorption and emission in the atmospheric window, and meanwhile, the pore size of the micro-nano-porous elastic film 1 is distributed between 0.3-200 μm and far away from the mid-infrared band, preferably 0.3-100 μm, which can effectively realize high visible light reflectivity. The bubble hole size of the micro-nano-porous elastic film 1 in Examples 1-9 is comparable to the wavelength of light, so the bubble hole can cause significant scattering of sunlight, and the white micro-nano-porous polymer has a diffuse reflection phenomenon to sunlight, thereby improving the reflectivity and emissivity of the composite film.

[0092] The visible light reflectivity and emissivity of Comparative Example 1 without the heat storage and emission functional layer 2 and Comparative Example 2 without the reflection functional layer 3 are both lower than that of Example 1, which indicates that the heat storage and emission functional layer 2 and the reflection functional layer 3 as functional coating can improve the visible light reflectivity and emissivity, thereby improving the radiation cooling performance of the product.

[0093] In Comparative Example 3 and Comparative Example 4, hollow nano-silicon spheres and paraffin are respectively used to replace the phase change microcapsules, because the phase change enthalpy of the phase change microcapsules of Example 1 is as high as 180 KJ / Kg, and the emissivity is above 90%, and the heat storage performance of the hollow nano-silicon spheres and paraffin is far inferior to that of the phase change microcapsules, so the phase change microcapsules are selected as the main raw material of the heat storage and emission functional layer 2 in Example 1, which can achieve good visible light reflection effect.

[0094] In Comparative Example 5, the vulcanization treatment is not performed in the process of preparing the micro-nano-porous elastic film 1, which affects the crosslinking of the elastomer and the formation of the bubble hole of the micro-nano-porous elastic film 1, and the bubble hole size is higher than that of Example 1, and the reflectivity and emissivity of the radiation cooling composite film in the 8-13 μm wavelength light are also lower than those of Example 1, which indicates that the vulcanization process is helpful to the formation of a compact and orderly distributed integrated micro-nano elastic film. The bubble hole size has a significant effect on the radiation cooling effect of the product.

[0095] In Comparative Example 6, the micro-nano-porous elastic film 1 is not subjected to hot pressing and cooling and setting first, but the functional coating is directly coated on the surface of the micro-nano-porous elastic film 1, so that the bubble hole size and thickness of the micro-nano-porous elastic film 1 are both significantly higher than those of Example 1, which indicates that the hot pressing / cooling setting can make the micro-nano-porous elastic film 1 change in thickness to a certain extent, and obtain a micro-nano-porous elastic film 1 with controllable thickness size. The bubble hole size exceeding 1 μm will affect the reflectivity and emissivity of the radiation cooling composite film in the 8-13 μm wavelength light, thereby reducing the radiation cooling effect of the product.

[0096] The elastic film of Comparative Example 7 is not impregnated with the supercritical fluid in step 2), i.e. only induced foaming by heating, which results in an increase in the pore size of the foamed elastic film, thereby causing a significant decrease in the visible light reflectivity, indicating that the pore size of the micro-nano-porous elastic film 1 has a great influence on the visible light reflectivity and emissivity, and the secondary foaming can control the pore size of the micro-nano-porous elastic film 1 in 0.3-1.0 μm, thereby obtaining the best radiation cooling effect.

[0097] In summary, the radiation cooling composite film of the present application comprises a micro-nano-porous elastic film 1 and a functional coating attached to the surface of the micro-nano-porous elastic film 1; wherein the micro-nano-porous elastic film 1 is obtained by foaming an elastic film, which has a micro-nano-cell structure, and using it as the substrate of the composite film can make the composite film have the advantages of light weight, softness and long service life, and also can cause strong Rayleigh scattering and Mie scattering when the composite film is irradiated by sunlight, thereby scattering the sunlight into the environment and greatly avoiding the absorption of heat, thereby achieving the passive radiation cooling effect. Different functional coatings are attached to the surface of the micro-nano-porous elastic film 1, including a heat storage and emission functional layer 2 and a reflective functional layer 3, so that the radiation cooling composite film has excellent radiation cooling effect, high and low temperature resistance, and effectively delays heat penetration, etc., and can be applied in the field of automotive interior, realizes the cooling and alleviation of high temperature in the vehicle, and can be mass-produced, and has the advantages of high processing efficiency.

[0098] Finally, it should be noted that the above examples are only used to illustrate the technical solutions of the present application and not to limit the protection scope of the present application, although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of the present application.

Claims

1. A radiative cooling composite film, characterized in that, The radiation cooling composite film comprises a micro-nano-porous elastic film and a functional coating attached to the surface of the micro-nano-porous elastic film; wherein the functional coating comprises, from bottom to top, a heat-accumulating and emitting functional layer and a reflecting functional layer; the heat-accumulating and emitting functional layer comprises phase-change microcapsules in the raw materials; the average particle size of the phase-change microcapsules is 0.1-10 μm; the phase-change microcapsules have a shell layer and a core layer, the shell layer comprises silicon dioxide, and the core layer comprises at least one of polyethylene glycol, paraffin, pentanetetrayl alcohol, neopentyl glycol and trimethylol ethane; the raw materials of the reflecting functional layer comprise nano functional particles; the nano functional particles comprise at least one of silicon dioxide, titanium dioxide, chromium dioxide, silicon nitride, aluminum phosphate and aluminum oxide; The preparation method of the radiation cooling composite film comprises the following steps: (1) foaming treatment of the elastic film to obtain the micro-nano-porous elastic film with micro-nano-porous structure; (2) hot pressing and cooling of the surface of the micro-nano-porous elastic film, and then sequentially compounding the functional coating on the surface of the micro-nano-porous elastic film to obtain the radiation cooling composite film; In the step (1), the foaming treatment comprises the following steps: first, immersing the elastic film in a supercritical fluid for the first foaming, and then continuing to heat for the second foaming to obtain the micro-nano-porous elastic film with micro-nano-porous structure; The preparation steps of the elastic film comprise, in sequence, preparation of a film, film lamination and vulcanization; wherein the temperature for preparing the film is 90-130 ℃, and the temperature for vulcanization is 160-190 ℃.

2. The radiative cooling composite film of claim 1, wherein, The pore size of the micro-nano-porous elastic film is 0.3-200 μm, and the porosity is 50-90%.

3. The radiative cooling composite film of claim 1, wherein, The elastic film comprises the following raw materials by weight: 50-100 parts of an elastomer, 0-20 parts of an inorganic oxide, 0-3 parts of a lubricant, 0-1 part of a crosslinking agent, and 0-0.5 part of an antioxidant.

4. The radiative cooling composite film of claim 3, wherein, The elastomer comprises at least one of a polyurethane thermoplastic elastomer, a polyester thermoplastic elastomer, a nylon elastomer, an EVA crosslinked elastomer, a polyolefin crosslinked elastomer, a styrene crosslinked elastomer and a vulcanized rubber.

5. The radiative cooling composite film of claim 1, wherein, The particle size of the nano functional particles is 0.05-10 μm.

6. The radiative cooling composite film of claim 1, wherein, The functional coating further comprises a waterproof functional layer arranged on the surface of the reflecting functional layer.

7. The radiative cooling composite film of claim 1, wherein, At least one of the following (I) and (II): (I) the preparation steps of the elastic film comprise, in sequence, mixing the raw materials for preparing the elastic film, co-extrusion of a double-screw extruder, casting, rolling and cooling to obtain the elastic film; (II) in the step (2), the temperature for hot pressing is 130-160 ℃, and the temperature for cooling is 4-15 ℃.

8. Use of the radiation cooling composite film according to any one of claims 1-7 in the preparation of automotive interiors.

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