Heat-insulating composite film material as well as preparation method and application thereof

Abstract

The invention provides a preparation method of a heat-insulating composite film material, which comprises the following steps: (1) stirring and mixing polytetrafluoroethylene powder, functional additive powder, a dispersing agent and a pore-foaming agent to obtain a mixed material; (2) melting the mixed material, casting into a thin film, and carrying out two-way stretching on the thin film by using a two-way stretching process to obtain a polytetrafluoroethylene composite microporous film; and (3) dipping the polytetrafluoroethylene composite microporous membrane into an aerogel solution, and drying to obtain the heat-insulating composite membrane material. According to the scheme, the functional additive is added in the preparation process to perform surface modification on the polytetrafluoroethylene, and a certain amount of dispersing agent and pore-foaming agent are supplemented, so that the heat-insulating composite film material with excellent dielectric property, heat-insulating property and mechanical property is prepared.

Description

Technical Field

[0001] The present invention relates to the technical field of heat insulation materials, and in particular to a heat insulation composite film material and a preparation method and application thereof. Background Art

[0002] As the power density of smartphones increases, the emergence of 5G millimeter wave antennas has brought some new challenges to thermal insulation. The surface temperature of the smartphone must not reach a temperature that is harmful to the user, which means that once the temperature rises, the smartphone will thermally throttle, that is, reduce the performance of the device. Due to the poor signal propagation of millimeter waves, these antennas are located near the surface of the device and can generate considerable heat. Therefore, higher requirements are placed on the temperature resistance and thermal insulation of the antenna material.

[0003] At present, most thermal insulation materials are prepared by composite of non-woven fabrics or glass fiber felt and aerogel to isolate the heat between the equipment and the antenna. However, this thermal insulation material not only has an adverse effect on the transmission of millimeter wave signals, but also has poor mechanical properties, thus failing to meet application requirements.

[0004] Based on this, there is an urgent need to provide a thermal insulation composite film material and a preparation method and application thereof. Summary of the invention

[0005] The embodiments of the present invention provide a thermal insulation composite film material and a preparation method and application thereof, which can solve the problem that the mechanical properties of traditional antenna thermal insulation materials are poor and they are prone to have an adverse effect on the transmission of millimeter wave signals.

[0006] In a first aspect, the present invention provides a method for preparing a thermal insulation composite film material, the preparation method comprising the following steps:

[0007] (1) mixing polytetrafluoroethylene powder, functional additive powder, dispersant and porogen to obtain a mixed material;

[0008] (2) casting the mixed material into an embryo and rolling it into a film, and biaxially stretching the film using a biaxial stretching process to obtain a polytetrafluoroethylene composite microporous membrane;

[0009] (3) Immersing the polytetrafluoroethylene composite microporous membrane into an aerogel solution, and obtaining the thermal insulation composite membrane material after drying.

[0010] Preferably, in step (1), the functional auxiliary agent is fluorinated ethylene propylene copolymer or polyvinylidene fluoride.

[0011] Preferably, in step (1), the mass ratio of the polytetrafluoroethylene to the functional additive is (10-30):1.

[0012] Preferably, in step (1), the dispersant is a cationic wetting dispersant, an anionic wetting dispersant, a nonionic wetting dispersant or an amphoteric wetting dispersant, and the porogen is a gas-generating porogen and a penetrating porogen.

[0013] Preferably, in step (1), in the mixed material, the content of the polytetrafluoroethylene is 50-70wt%, and the content of the dispersant and the porogen is 20-35wt% respectively.

[0014] Preferably, in step (2), the temperature of the cast embryo extrusion is 35-45°C, and the temperature of the biaxial stretching is 200-300°C.

[0015] Preferably, in step (2), after biaxially stretching the film, the method further comprises sintering the stretched film.

[0016] More preferably, the sintering temperature is 280-340° C., and the sintering time is 10 s-2 min.

[0017] Preferably, before step (3), the method further comprises the step of plasma treating the polytetrafluoroethylene composite microporous membrane.

[0018] Preferably, in step (3), the aerogel solution comprises a silica aerogel solution, a polyimide aerogel solution or an alumina aerogel solution; wherein the mass concentration of the aerogel solution is 40-45%.

[0019] More preferably, the content of aerogel loaded in the polytetrafluoroethylene composite microporous membrane is 20-50wt%.

[0020] Preferably, in step (3), the drying method is freeze drying, supercritical drying or normal pressure drying.

[0021] In a second aspect, the present invention provides a thermal insulation composite film material, which is prepared by the preparation method described in any one of the first aspects above.

[0022] In a third aspect, the present invention provides an application of the thermal insulation composite film material described in the second aspect to isolate heat transfer between a smart device and an antenna.

[0023] Compared with the prior art, the present invention has at least the following beneficial effects:

[0024] (1) In the present invention, polytetrafluoroethylene powder is firstly stirred and mixed with functional auxiliary agent powder, dispersant and porogen to form a mixed material, and the mixed material is used as a raw material to prepare a polytetrafluoroethylene composite microporous membrane with low dielectric properties through a biaxial stretching process, and finally the microporous membrane is immersed in an aerogel solution, and the aerogel particles can be loaded onto the surface of the microporous membrane through the pores, thereby forming a thermal insulation composite membrane material with the aerogel. In the preparation process, the surface of polytetrafluoroethylene is firstly modified by selecting a suitable functional auxiliary agent, which can reduce the dielectric constant of polytetrafluoroethylene. The dielectric properties of the polytetrafluoroethylene composite microporous membrane can improve the bonding performance of the subsequent aerogel and the polytetrafluoroethylene composite microporous membrane, and can ensure the mechanical strength of the thermal insulation composite membrane material; at the same time, the addition of the porogen can effectively prevent the mutual adhesion between polytetrafluoroethylene and the functional additives to cause pore closure, and further supplemented with a specific type of dispersant to further ensure the good interface bonding performance between the subsequent aerogel and the polytetrafluoroethylene composite microporous membrane. In this way, a thermal insulation composite membrane material with excellent dielectric properties, thermal insulation properties and mechanical properties is prepared;

[0025] (2) The density of the thermal insulation composite film material prepared by the present invention is ≤80kg / m 3 , thermal conductivity ≤0.022w / mk, tensile strength ≥40Mpa, dielectric constant ≤2, which can effectively isolate the heat transfer between smart devices and antennas without affecting the transmission of millimeter wave signals. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0027] Figure 1 This is a flow chart of a method for preparing a thermal insulation composite film material provided by an embodiment of the present invention;

[0028] Figure 2 This is a scanning electron microscope (SEM) image of a thermal insulation composite film material provided in Example 1 of the present invention. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0030] like Figure 1 As shown, an embodiment of the present invention provides a method for preparing a thermal insulation composite film material, and the preparation method comprises the following steps:

[0031] (1) mixing polytetrafluoroethylene powder, functional additive powder, dispersant and porogen to obtain a mixed material;

[0032] (2) casting the mixed material into an embryo and rolling it into a film, and biaxially stretching the film using a biaxial stretching process to obtain a polytetrafluoroethylene composite microporous membrane;

[0033] (3) Immersing the polytetrafluoroethylene composite microporous membrane into an aerogel solution, and obtaining the thermal insulation composite membrane material after drying.

[0034] In the embodiment of the present invention, polytetrafluoroethylene powder is firstly stirred and mixed with functional auxiliary agent powder, dispersant and porogen to form a mixed material, and the mixed material is used as a raw material to prepare a polytetrafluoroethylene composite microporous membrane with lower dielectric properties through a biaxial stretching process, and finally the microporous membrane is immersed in an aerogel solution, and the aerogel particles can be loaded to the surface of the microporous membrane through the pores, thereby forming a thermal insulation composite membrane material by compounding with the aerogel. In the preparation process, the surface of polytetrafluoroethylene is firstly modified by selecting a suitable functional auxiliary agent, which can reduce the dielectric properties of the polytetrafluoroethylene composite microporous membrane on the one hand, and make the subsequent bonding performance of the aerogel and the polytetrafluoroethylene composite microporous membrane better on the other hand, and can ensure the mechanical strength of the thermal insulation composite membrane material; at the same time, the addition of the porogen can effectively prevent the mutual adhesion between polytetrafluoroethylene and the functional auxiliary agent to cause pore closure, and further supplemented with a specific type of dispersant, so as to further ensure the good interface bonding performance between the subsequent aerogel and the polytetrafluoroethylene composite microporous membrane, so that a thermal insulation composite membrane material with excellent dielectric properties, thermal insulation properties and mechanical properties is prepared.

[0035] According to some preferred embodiments, the functional auxiliary agent is a fluorinated ethylene propylene copolymer or polyvinylidene fluoride.

[0036] In the embodiment of the present invention, fluorinated ethylene propylene copolymer or polyvinylidene fluoride is used as a functional auxiliary agent to mix with polytetrafluoroethylene powder to prepare a polytetrafluoroethylene composite microporous membrane. Since the melting point of the functional auxiliary agent is relatively low, the molten functional auxiliary agent can be dispersed in the polytetrafluoroethylene microporous membrane during the biaxial stretching process. On the one hand, this type of functional auxiliary agent has a relatively low dielectric constant. Mixing it with polytetrafluoroethylene powder can further reduce the dielectric properties of the polytetrafluoroethylene composite microporous membrane. On the other hand, this type of functional auxiliary agent can not only improve the surface of the polytetrafluoroethylene composite microporous membrane, but also improve the dielectric properties of the polytetrafluoroethylene composite microporous membrane. The functional additive can reduce the inertness of the surface of the polytetrafluoroethylene composite microporous membrane and increase the porosity of the polytetrafluoroethylene composite microporous membrane, so that when the microporous membrane is subsequently mixed with an aerogel solution, more aerogel particles can be dispersed in the pores of the microporous membrane and the bonding performance of the aerogel and the microporous membrane can be enhanced. Furthermore, the addition of the above-mentioned functional additive can prevent the polytetrafluoroethylene composite microporous membrane from shrinking at high temperatures and improve the dimensional stability and modulus of the composite membrane, which is conducive to the preparation of a heat-insulating composite membrane material that is not easy to fall off, has good high temperature resistance, low dielectric properties and good mechanical strength.

[0037] According to some preferred embodiments, the mass ratio of the polytetrafluoroethylene to the functional additive is (10-30):1 (for example, it can be 10:1, 15:1, 20:1, 25:1 or 30:1).

[0038] In the embodiment of the present invention, by reasonably controlling the mass ratio between polytetrafluoroethylene and the functional additive, it is beneficial to prepare a heat-insulating composite membrane material that is not easy to shed powder, has good high temperature resistance, low dielectric properties and good mechanical strength, and can ensure strong bonding performance between the aerogel and the microporous membrane; it has been confirmed by experiments of the present invention that if the addition amount of the functional additive is low, the porosity of the polytetrafluoroethylene composite microporous membrane will be low, which is not conducive to the dispersion of aerogel particles in the pores of the microporous membrane, and is not conducive to ensuring good bonding performance between the aerogel and the microporous membrane, thereby not being conducive to ensuring good thermal insulation performance and low dielectric properties of the composite membrane material, and if the addition amount of the functional additive is too high, the porosity of the polytetrafluoroethylene composite microporous membrane will be too high, which not only makes the strength of the final composite membrane material low, but also easily causes the composite membrane material to shed powder.

[0039] According to some preferred embodiments, the dispersant is a cationic wetting dispersant, an anionic wetting dispersant, a nonionic wetting dispersant or an amphoteric wetting dispersant, and the porogen is a gas generating porogen and a permeable porogen; in the mixed material, the content of polytetrafluoroethylene is 50-70wt% (for example, it can be 50wt%, 55wt%, 60wt%, 65wt% or 70wt%), and the content of the dispersant and the porogen is both 20-35wt% (for example, it can be 20wt%, 22wt%, 25wt%, 28wt%, 30wt% or 35wt%).

[0040] In the embodiment of the present invention, in the process of preparing the polytetrafluoroethylene composite microporous membrane, on the basis of the functional additive, a certain type and amount of dispersant and porogen are further added, and the addition of the dispersant can enhance the subsequent dispersion of the aerogel in the pores of the microporous membrane, thereby further enhancing the interface bonding between the aerogel and the microporous membrane, and the addition of the porogen can not only effectively prevent the pore closure caused by fiber adhesion between the polytetrafluoroethylene and the functional additive, but also make the reflection of the dispersant more uniform, so that the aerogel is evenly distributed in the pores of the polytetrafluoroethylene composite microporous membrane, thereby ensuring the uniformity of the overall performance of the thermal insulation composite membrane material.

[0041] The experiments of the present invention have confirmed that if the content of the dispersant and the porogen is too high, it is not only not conducive to effectively enhancing the interface bonding between the aerogel and the microporous membrane and the uniformity of the overall performance of the thermal insulation composite membrane material, but also easily leads to difficulty in forming the polytetrafluoroethylene composite microporous membrane. If the content of the dispersant and the porogen is too low, the processing performance of the polytetrafluoroethylene composite microporous membrane will be poor.

[0042] At the same time, it should be noted that the specific types of porogens and dispersants in the embodiments of the present invention can be selected from the types provided above. For example, the gas-generating porogen can be ammonium bicarbonate, sodium bicarbonate, or hydrogen peroxide, and the permeable porogen can be sodium chloride or potassium chloride; the cationic wetting and dispersing agent can be amine salts or quaternary ammonium salts, the anionic wetting and dispersing agent can be sodium oleate, carboxylates, or sulfates, the nonionic wetting and dispersing agent can be alkyl alcohol amides or polyol monofatty acid esters, and the amphoteric wetting and dispersing agent can be amino oleate.

[0043] According to some preferred embodiments, the casting embryo pushing temperature is 35-45°C (for example, it can be 35°C, 38°C, 40°C, 42°C or 45°C), and the temperature of the biaxial stretching is 200-300°C (for example, it can be 200°C, 220°C, 240°C, 250°C, 280°C or 300°C).

[0044] In the embodiment of the present invention, during the forming process of the polytetrafluoroethylene composite microporous membrane, the mixed material can first be extruded into a casting blank at a certain temperature and rolled into a film of a certain thickness, and then the film can be stretched in the length direction and the width direction respectively by a biaxial stretching process under a certain temperature and tensile force. Specifically, by controlling the stretching ratio in the length direction to 5-12 times and the stretching ratio in the width direction to 3-15 times, it is beneficial to form a polytetrafluoroethylene composite microporous membrane with uniform porosity, good tensile properties and good shape stability under high temperature and high pressure.

[0045] According to some preferred embodiments, in step (2), after biaxially stretching the film, the step further includes sintering the stretched film; the sintering temperature is 280-340°C (for example, it can be 280°C, 290°C, 300°C, 310°C, 320°C, 330°C or 340°C), and the time is 10s-2min (for example, it can be 10s, 20s, 30s, 1min, 90s or 2min).

[0046] In the embodiment of the present invention, after biaxially stretching the film, the film is sintered within the above temperature range, which is beneficial to improving the strength and dimensional stability of the composite film.

[0047] According to some preferred embodiments, before step (3), the method further includes subjecting the polytetrafluoroethylene composite microporous membrane to plasma treatment.

[0048] Considering that the prepared polytetrafluoroethylene composite microporous membrane has certain hydrophobic properties, which is not conducive to the subsequent good composite of the microporous membrane and the aerogel, therefore, in the embodiment of the present invention, after obtaining the polytetrafluoroethylene composite microporous membrane, it is plasma treated to improve the surface properties of the microporous membrane, which is beneficial to further enhance the bonding strength between the microporous membrane and the aerogel.

[0049] According to some preferred embodiments, in step (3), the aerogel solution includes a silica aerogel solution, a polyimide aerogel solution or an alumina aerogel solution; wherein the mass concentration of the aerogel solution is 40-45% (for example, it can be 40%, 41%, 42%, 43%, 44% or 45%); the content of the polytetrafluoroethylene composite microporous membrane loaded with aerogel is 20-50wt% (for example, it can be 20wt%, 30wt%, 40wt% or 50wt%).

[0050] In the embodiment of the present invention, during compounding, under normal temperature conditions, by completely immersing the polytetrafluoroethylene composite microporous membrane in the above-mentioned type of aerogel solution, the aerogel solution particles will be loaded on the microporous membrane through the pores of the microporous membrane. Furthermore, by controlling the immersion time, the aerogel loading amount on the surface of the microporous membrane is controlled within the above-mentioned range, which is conducive to ensuring that the thermal insulation composite membrane material has both excellent thermal insulation performance and low dielectric properties. If the loading amount is too high or too low, the balance between the dielectric properties and the thermal insulation performance of the thermal insulation composite membrane material will be destroyed, which is not conducive to obtaining a thermal insulation composite membrane material with excellent thermal insulation performance, low dielectric properties and good mechanical strength.

[0051] According to some preferred embodiments, in step (3), the drying method is freeze drying, supercritical drying or normal pressure drying.

[0052] It should be noted that there is no particular limitation on the specific parameters of the above drying method in the embodiment of the present invention, and the parameters can be adjusted according to the drying requirements in the actual process.

[0053] An embodiment of the present invention further provides a thermal insulation composite film material, which is prepared by any of the preparation methods described above.

[0054] An embodiment of the present invention further provides an application of the above-mentioned thermal insulation composite film material in isolating heat transfer between a smart device and an antenna.

[0055] The density of the thermal insulation composite film material prepared by the above method in the embodiment of the present invention is ≤80kg / m 3 , thermal conductivity ≤0.022w / mk, tensile strength ≥40Mpa, dielectric constant ≤2, which can effectively isolate the heat transfer between smart devices and antennas without affecting the transmission of millimeter wave signals.

[0056] In order to more clearly illustrate the technical solution and advantages of the present invention, a thermal insulation composite film material and a preparation method and application thereof are described in detail below through several embodiments.

[0057] Embodiment 1:

[0058] (1) 300 g of polytetrafluoroethylene powder, 10 g of functional additive powder (fluorinated ethylene propylene copolymer), 110 g of dispersant (sodium oleate) and 110 g of porogen (ammonium bicarbonate) were stirred and mixed to obtain a mixed material;

[0059] (2) extruding the mixed material at 45° C. into a cast embryo and rolling it into a strip film, and biaxially stretching the film at 250° C. using a biaxial stretching process to obtain a polytetrafluoroethylene composite microporous membrane; wherein the stretching ratio in the length direction is 8 times, and the stretching ratio in the width direction is 5 times;

[0060] (3) At room temperature (25° C.), immersing the polytetrafluoroethylene composite microporous membrane in a silica aerogel precursor solution having a mass concentration of 40% for 4 minutes, and freeze-drying the solution to obtain a thermal insulation composite membrane material; wherein the content of the aerogel loaded in the polytetrafluoroethylene composite microporous membrane is 30 wt %.

[0061] Embodiment 2:

[0062] (1) 400 g of polytetrafluoroethylene powder, 20 g of functional additive powder (polyvinylidene fluoride), 150 g of dispersant (sodium oleate) and 150 g of porogen (ammonium bicarbonate) were stirred and mixed to obtain a mixed material;

[0063] (2) Extruding the mixed material at 40° C. and rolling it into a strip film, and biaxially stretching the film at 300° C. using a biaxial stretching process to obtain a polytetrafluoroethylene composite microporous membrane; wherein the stretching ratio in the length direction is 10 times, and the stretching ratio in the width direction is 10 times;

[0064] (3) At room temperature of 25° C., the polytetrafluoroethylene composite microporous membrane was immersed in a polyimide aerogel solution with a mass concentration of 45% for 4 minutes, and then freeze-dried to obtain a thermal insulation composite membrane material; wherein the content of the aerogel loaded on the polytetrafluoroethylene composite microporous membrane was 30wt%.

[0065] Embodiment 3:

[0066] (1) 400 g of polytetrafluoroethylene powder, 30 g of functional additive powder (fluorinated ethylene propylene copolymer), 150 g of dispersant (sodium oleate) and 150 g of porogen (ammonium bicarbonate) were stirred and mixed to obtain a mixed material;

[0067] (2) Extruding the mixed material at 30° C. and rolling it into a strip film, and biaxially stretching the film at 200° C. using a biaxial stretching process to obtain a polytetrafluoroethylene composite microporous membrane; wherein the stretching ratio in the length direction is 12 times, and the stretching ratio in the width direction is 15 times;

[0068] (3) At room temperature of 25° C., the polytetrafluoroethylene composite microporous membrane was immersed in an alumina aerogel solution with a mass concentration of 40% for 5 minutes, and then freeze-dried to obtain a thermal insulation composite membrane material; wherein the content of the aerogel loaded in the polytetrafluoroethylene composite microporous membrane was 30wt%.

[0069] Embodiment 4:

[0070] Example 4 is basically the same as Example 1, except that in step (1), the amount of functional auxiliary agent powder added is 5 g.

[0071] Embodiment 5:

[0072] Example 5 is basically the same as Example 1, except that in step (1), the amount of functional auxiliary agent powder added is 80 g.

[0073] Embodiment 6:

[0074] Example 6 is substantially the same as Example 1, except that in step (1), the amount of porogen added is 80 g.

[0075] Embodiment 7:

[0076] Example 7 is substantially the same as Example 1, except that in step (1), 80 g of dispersant is added.

[0077] Embodiment 8:

[0078] Example 8 is substantially the same as Example 1, except that in step (2), the temperature of biaxial stretching is 180°C.

[0079] Embodiment 9:

[0080] Example 9 is substantially the same as Example 1, except that in step (2), the temperature of biaxial stretching is 350°C.

[0081] Embodiment 10:

[0082] Example 10 is substantially the same as Example 1, except that in step (3), the content of aerogel loaded on the polytetrafluoroethylene composite microporous membrane is 10 wt %.

[0083] Embodiment 11:

[0084] Example 11 is substantially the same as Example 1, except that in step (3), the content of aerogel loaded on the polytetrafluoroethylene composite microporous membrane is 60 wt%.

[0085] Comparative Example 1:

[0086] Comparative Example 1 is substantially the same as Example 1, except that in step (1), no functional additive is added.

[0087] Comparative Example 2:

[0088] Comparative Example 2 is substantially the same as Example 1, except that in step (1), no dispersant is added.

[0089] Comparative Example 3:

[0090] Comparative Example 3 is substantially the same as Example 1, except that in step (1), no porogen is added.

[0091] Comparative Example 4:

[0092] Comparative Example 4 is basically the same as Example 1, in which glass fiber felt is compounded with 40% silica aerogel precursor, and a supercritical drying process is used to obtain glass fiber aerogel needle-punched felt.

[0093] The thermal insulation composite film materials (hereinafter referred to as samples) prepared in Examples 1 to 11 and Comparative Examples 1 to 4 were subjected to performance tests, and the test results are shown in Table 1; wherein, the density, thermal conductivity and tensile strength were tested with reference to GB / T34336-2017 "Nanoporous aerogel composite insulation products", and the dielectric constant was tested with reference to GB / T 1409-2006 "Recommended method for measuring the permittivity and dielectric loss factor of electrical insulating materials at industrial frequency, audio frequency and high frequency (including meter wave wavelength)".

[0094] Table 1

[0095]

[0096] As shown in Table 1, compared with the heat-insulating composite membrane material in the comparative example, the polytetrafluoroethylene composite microporous membrane is prepared by mixing polytetrafluoroethylene with a functional additive, a dispersant and a porogen in the embodiment of the present invention, and aerogel is further composited on the surface thereof to obtain a heat-insulating composite membrane material with good high temperature resistance, low dielectric properties and good mechanical strength. Figure 1 It can be seen that aerogel, polytetrafluoroethylene and functional additives are uniformly dispersed in the thermal insulation composite membrane material and are interconnected through the functional additives, which is conducive to ensuring that the aerogel is uniformly dispersed in the polytetrafluoroethylene microporous membrane and is not prone to powdering.

[0097] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a thermal insulation composite film material, characterized in that: The preparation method comprises the following steps: (1) mixing polytetrafluoroethylene powder, functional additive powder, dispersant and porogen to obtain a mixed material; (2) casting the mixed material into an embryo and rolling it into a film, and biaxially stretching the film using a biaxial stretching process to obtain a polytetrafluoroethylene composite microporous membrane; (3) Immersing the polytetrafluoroethylene composite microporous membrane into an aerogel solution, and obtaining the thermal insulation composite membrane material after drying.

2. The preparation method according to claim 1, characterized in that: In step (1), the functional additive is a fluorinated ethylene-propylene copolymer or polyvinylidene fluoride; Preferably, the mass ratio of the polytetrafluoroethylene to the functional additive is (10-30):

1.

3. The preparation method according to claim 1, characterized in that: In step (1), the dispersant is a cationic wetting dispersant, an anionic wetting dispersant, a nonionic wetting dispersant or an amphoteric wetting dispersant, and the porogen is a gas-generating porogen and a penetrating porogen; Preferably, in the mixed material, the content of the polytetrafluoroethylene is 50-70wt%, and the content of the dispersant and the porogen is 20-35wt% respectively.

4. The preparation method according to claim 1, characterized in that: In step (2), the temperature of the cast embryo extrusion is 35-45°C, and the temperature of the biaxial stretching is 200-300°C.

5. The preparation method according to claim 1, characterized in that: In step (2), after biaxially stretching the film, the method further comprises sintering the stretched film; Preferably, the sintering temperature is 280-340° C., and the sintering time is 10 s-2 min.

6. The preparation method according to claim 1, characterized in that: Before step (3), the method further includes a step of plasma treating the polytetrafluoroethylene composite microporous membrane.

7. The preparation method according to claim 1, characterized in that: In step (3), the aerogel solution includes a silica aerogel solution, a polyimide aerogel solution or an alumina aerogel solution; wherein the mass concentration of the aerogel solution is 40-45%; Preferably, the content of aerogel loaded in the polytetrafluoroethylene composite microporous membrane is 20-50wt%.

8. The preparation method according to claim 1, characterized in that: In step (3), the drying method is freeze drying, supercritical drying or normal pressure drying.

9. A thermal insulation composite film material, characterized in that: The preparation method is described in any one of claims 1 to 8.

10. Use of the thermal insulation composite film material according to claim 9 in isolating heat transfer between a smart device and an antenna.

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