A method for preparing polyimide-aluminum heat-insulating and sound-absorbing composite foam and its product

Abstract

The invention discloses a method for preparing a polyimide-aluminum heat-insulating sound-absorbing composite foam and a product, comprising the following steps: (1), mixing an aromatic anhydride derivative solution dissolved by a polar solvent, a catalyst, a foam stabilizer and a foaming agent to obtain a foaming white material; (2), adding isocyanate to the foaming white material and mixing to obtain a foaming slurry; (3), first pouring 50-70% of the foaming slurry into an open mold, then pressing the open-cell aluminum foam into the foaming slurry, and finally pouring the remaining foaming slurry evenly into the mold, the foaming slurry is foamed and formed in the mold, and the aluminum foam composited by the polyimide foam intermediate is obtained after standing; (4), taking out the aluminum foam composited by the polyimide foam intermediate, and high-temperature curing the aluminum foam composited by the polyimide foam intermediate to obtain a polyimide-aluminum heat-insulating sound-absorbing composite foam. The present invention has the characteristics of being able to improve the sound absorption coefficient, broaden the sound absorption frequency band, and improve the thermal insulation effect.

Description

Technical Field

[0001] The invention relates to a composite foam material and a preparation method thereof, in particular to a preparation method and product of a polyimide-aluminum heat-insulating and sound-absorbing composite foam. Background Art

[0002] Open-cell aluminum foam is a metal foam material with aluminum as the matrix and a pore structure inside. Due to its unique pore structure and permeability, especially the large porosity of open-cell aluminum foam, after pressing, the pores are connected, and it has good sound absorption performance. At the same time, open-cell aluminum foam also has excellent properties such as light weight, heat resistance, shock resistance, corrosion resistance, recyclability and machinability. These properties make it have broad application prospects in today's material field and is a promising engineering material. It is widely used in national defense and security fields (such as engine compartments of various ships), road traffic fields (such as sound absorption barriers), vehicle and ship manufacturing fields (such as front and rear fenders, trunk lids) and construction fields (such as recording studios, concert halls, conference halls, stadiums, etc.).

[0003] However, during the application process, people also found that open-cell foam aluminum has some shortcomings. For example, the sound absorption coefficient of open-cell foam aluminum varies greatly between high and low frequencies; the sound absorption coefficient at medium and low frequencies is low, and the sound absorption effect is poor. These shortcomings seriously restrict the in-depth and cutting-edge application of foam aluminum materials in complex sound field environments and medium and low frequency acoustic applications.

[0004] At present, there are two main methods to improve the defects of foam aluminum in sound absorption. One is to make perforated sound-absorbing foam aluminum by mechanical processing. CN2712945 discloses a perforated sound-absorbing foam aluminum, which changes the acoustic impedance of the foam aluminum material by perforation, and forms a composite sound-absorbing structure composed of sound-absorbing material layers with different acoustic impedances by layered processing, so as to obtain better sound absorption performance. The second is to use a composite sound-absorbing structure to combine foam aluminum with other materials to obtain a material with excellent sound absorption performance. CN204551295U discloses a full-screen sound absorption and noise reduction device, the sound-absorbing material layer is foam rubber, foam ceramic and foam aluminum, and the design of the multi-layer sound-absorbing structure improves the sound absorption performance of the screen and increases the sound absorption frequency band; CN108564938A discloses a new bionic composite sound-absorbing structure, which consists of four parts: fiber, film, hollow cylinder and porous foam aluminum. Compared with the existing traditional foam aluminum sound-absorbing structure, this design reduces the cost and weight and increases the sound absorption coefficient.

[0005] Although the above methods have improved the sound absorption performance of aluminum foam to a certain extent, the holes of the first method are usually difficult to meet the small and dense requirements for controlling low-frequency noise due to mechanical process reasons, so the sound absorption effect of low-frequency noise is not very ideal, and the processing process is time-consuming and labor-intensive; the second method has a complex production process and uses too many materials, and the sound-absorbing cotton and other materials currently used have low strength, are easy to age, and affect the sound absorption effect after being damp. At the same time, although the above methods can improve the sound absorption performance of aluminum foam to a certain extent, they are only limited to the improvement of the sound absorption coefficient in the existing sound absorption frequency band. The starting sound absorption frequency point (the frequency at which the sound absorption coefficient first reaches 0.2) is still between 2-3kHz, and the entire sound absorption frequency band has not been effectively widened. In addition, open-cell aluminum foam has a large specific surface area, the pore space is interconnected, the internal fluid is convenient for heat exchange, and the thermal insulation effect is poor, making the open-cell aluminum foam extremely susceptible to the surrounding environment in practical applications. This feature also limits the use of open-cell aluminum foam.

[0006] Therefore, the existing technology has the problems of low sound absorption coefficient, narrow sound absorption frequency band and poor heat insulation effect. Summary of the invention

[0007] The purpose of the present invention is to improve the heat insulation and sound absorption performance of open-cell aluminum foam by using cross-disciplinary knowledge and technology without changing its light weight and other properties, and to provide a method and product for preparing a polyimide-aluminum heat insulation and sound absorption composite foam. The present invention has the characteristics of being able to increase the sound absorption coefficient, broaden the sound absorption frequency band, and improve the heat insulation effect.

[0008] The technical solution of the present invention is a method for preparing a polyimide-aluminum heat-insulating and sound-absorbing composite foam, comprising the following steps:

[0009] (1) mixing a solution of an aromatic anhydride derivative dissolved in a polar solvent, a catalyst, a foam stabilizer and a foaming agent to obtain a foaming white material;

[0010] (2) adding isocyanate to the foaming white material and mixing to obtain a foaming slurry;

[0011] (3) First, pour 50-70% of the foaming slurry into an open mold, then press the open-cell foamed aluminum into the foaming slurry, and finally pour the remaining foaming slurry evenly into the mold. The foaming slurry is foamed and formed in the mold, and after standing, a foamed aluminum composited with a polyimide foam intermediate is obtained;

[0012] (4) taking out the aluminum foam composited with the polyimide foam intermediate, and subjecting the aluminum foam composited with the polyimide foam intermediate to high-temperature curing to obtain a polyimide-aluminum heat-insulating and sound-absorbing composite foam.

[0013] In the aforementioned method for preparing a polyimide-aluminum heat-insulating and sound-absorbing composite foam, the weight ratio of the aromatic anhydride derivative solution dissolved in a polar solvent, the catalyst, the foam stabilizer, the foaming agent and the isocyanate is 50-100:4-8:12-24:6-12:75-150.

[0014] In the aforementioned method for preparing the polyimide-aluminum heat-insulating and sound-absorbing composite foam, the solid content of the aromatic anhydride derivative solution is 20%-85%.

[0015] In the aforementioned method for preparing a polyimide-aluminum heat-insulating and sound-absorbing composite foam, the bottom area of ​​the open-cell aluminum foam is 64%-81% of the bottom area of ​​the mold cavity, and the thickness of the open-cell aluminum foam is 5%-10% of the mold depth; the mass ratio of the foaming slurry to the volume of the mold cavity is: 0.01-0.10 g / cm 3 ; The density of open-cell aluminum foam is 280-350kg / m 3 .

[0016] The density of the polyimide foam intermediate in step (3) is 7-20 kg / m 3 .

[0017] In the aforementioned method for preparing a polyimide-aluminum thermal insulation and sound-absorbing composite foam, the aromatic anhydride derivative is a mixture of one or more of dimethyl pyromellitic acid, diethyl pyromellitic acid, 3,3',4,4'-dimethyl benzophenone tetracarboxylate, 3,3',4,4'-diethyl benzophenone tetracarboxylate, 3,3',4,4'-dimethyl diphenyl ether tetracarboxylate, 3,3',4,4'-diethyl diphenyl ether tetracarboxylate, 3,3',4,4'-dimethyl biphenyl sulfone tetracarboxylate or 3,3',4,4'-diethyl biphenyl sulfone tetracarboxylate;

[0018] The polar solvent is a mixture of one or more of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone or dimethyl sulfoxide.

[0019] In the aforementioned method for preparing a polyimide-aluminum heat-insulating and sound-absorbing composite foam, the catalyst is a mixture of one or more of triethanolamine, triethylenediamine, stannous octoate, dibutyltin dilaurate or Dabco33-LV;

[0020] The foam stabilizer is a mixture of one or more of non-hydrolyzable water-soluble polyether siloxane, non-ionic fluorocarbon compound or polyethylene oxide;

[0021] The foaming agent is water;

[0022] The isocyanate is a mixture of one or more of diphenylmethane diisocyanate, xylene isocyanate or polyphenyl polymethylene polyisocyanate.

[0023] In the aforementioned method for preparing a polyimide-aluminum thermal insulation and sound absorption composite foam, in step (1), the temperature of the foaming white material is maintained between 0-15°C; in step (2), the temperature of the isocyanate is maintained between 0-15°C.

[0024] In the aforementioned method for preparing the polyimide-aluminum heat-insulating and sound-absorbing composite foam, the high-temperature curing in step (4) is to place the polyimide foam intermediate composited with the foamed aluminum into a high-temperature forced air drying oven at 140-220° C. and heat for 0.5-3 hours.

[0025] A polyimide-aluminum heat-insulating and sound-absorbing composite foam is prepared by the above-mentioned preparation method of the polyimide-aluminum composite foam.

[0026] In the aforementioned polyimide-aluminum thermal insulation and sound absorption composite foam, the thermal conductivity of the polyimide-aluminum thermal insulation and sound absorption composite foam is 0.070-0.085 W / m·K, the initial sound absorption frequency point is 400-700 Hz, and the density is 287-370 kg / m 3 .

[0027] Compared with the prior art, the present invention fills polyimide foam in the pores of open-cell aluminum foam to improve the thermal insulation and sound absorption properties of aluminum foam and broaden the sound absorption frequency band without changing the light weight and other properties of open-cell aluminum foam, thereby obtaining a polyimide-aluminum foam composite material with better thermal insulation performance, stronger sound absorption ability and a wide range of applications.

[0028] Specifically:

[0029] In the first aspect, the present invention effectively adjusts the pore structure of the polyimide foam compounded in the final product by strictly controlling the usage ratio of the aromatic anhydride derivative solution dissolved in a polar solvent, the catalyst, the foam stabilizer, the foaming agent and the isocyanate, strictly controlling the size ratio of the open-cell foam aluminum to the inner cavity of the mold, and controlling the mass of the foaming slurry to the volume ratio of the inner cavity of the mold, thereby effectively ensuring the excellent sound absorption and heat insulation performance of the final product in the full frequency range.

[0030] Secondly, the density of the polyimide-aluminum composite foam material prepared by the present invention is similar to that of the original open-cell aluminum foam, which maintains the lightweight characteristics of aluminum foam and can still be used as a lightweight material in various fields. On this basis, the thermal insulation performance is greatly improved and the sound absorption frequency band is broadened, which makes the use of aluminum foam wider and less susceptible to the surrounding environment.

[0031] Thirdly, the present invention can achieve excellent sound absorption and heat insulation performance without the need for additional filling of different functional particles.

[0032] After testing, compared with the thermal conductivity of pure foam aluminum of 0.25-0.40W / (m·K), the thermal conductivity of polyimide-aluminum insulation and sound absorption composite foam decreased by 66-83%, between 0.070-0.085W / (m·K); the initial sound absorption frequency point was 400-700Hz, and the sound absorption frequency range was widened to 2.2-2.8kHz at low frequencies, and the average sound absorption coefficient in the widened frequency band was 0.45-0.55; the average sound absorption coefficient of pure foam aluminum from the initial sound absorption frequency point to 6.4KHz was 0.60-0.65, while the average sound absorption coefficient of polyimide-aluminum composite foam in the above frequency band was 0.70-0.75, thereby effectively improving the sound absorption coefficient; at the same time, compared with the pure foam aluminum of 280-350kg / m 3 The density of polyimide-aluminum composite foam is only increased by 7-20kg / m 3 , that is 2.3%-6.6%.

[0033] In summary, the present invention has the characteristics of being able to increase the sound absorption coefficient, broaden the sound absorption frequency band and improve the heat insulation effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is a diagram of the open-cell aluminum foam sample used in Examples 2, 3, and 4 of the present invention.

[0035] Figure 2 It is a sound absorption curve diagram of pure foam aluminum and polyimide-aluminum thermal insulation and sound absorption composite foam material in Example 2 of the present invention. DETAILED DESCRIPTION

[0036] The present invention is further described below in conjunction with the accompanying drawings and embodiments, but they are not intended to limit the present invention.

[0037] Example 1. A method for preparing a polyimide-aluminum heat-insulating and sound-absorbing composite foam comprises the following steps:

[0038] (1) mixing a solution of an aromatic anhydride derivative dissolved in a polar solvent, a catalyst, a foam stabilizer and a foaming agent to obtain a foaming white material;

[0039] (2) adding isocyanate to the foaming white material and mixing to obtain a foaming slurry;

[0040] (3) First, pour 50-70% of the foaming slurry into an open mold (a round mold can be selected), then press the open-cell foamed aluminum into the foaming slurry, and finally pour the remaining foaming slurry evenly into the mold. The foaming slurry is foamed and formed in the mold, and after standing, the foamed aluminum composited with the polyimide foam intermediate is obtained;

[0041] (4) taking out the aluminum foam composited with the polyimide foam intermediate, and subjecting the aluminum foam composited with the polyimide foam intermediate to high-temperature curing to obtain a polyimide-aluminum heat-insulating and sound-absorbing composite foam.

[0042] The weight ratio of the aromatic anhydride derivative solution dissolved in the polar solvent, the catalyst, the foam stabilizer, the foaming agent and the isocyanate is 50-100:4-8:12-24:6-12:75-150.

[0043] The solid content of the aromatic anhydride derivative solution is 20%-85%.

[0044] The bottom area of ​​the open-cell aluminum foam is 64%-81% of the bottom area of ​​the mold cavity, and the thickness of the open-cell aluminum foam is 5%-10% of the mold depth; the mass ratio of the foaming slurry to the volume of the mold cavity is: 0.01-0.10g / cm 3 ; The density of open-cell aluminum foam is 280-350kg / m 3

[0045] The density of the polyimide foam intermediate in step (3) is 7-20 kg / m 3 .

[0046] The aromatic anhydride derivative is a mixture of one or more of dimethyl pyromellitic acid, diethyl pyromellitic acid, dimethyl 3,3',4,4'-benzophenone tetracarboxylate, diethyl 3,3',4,4'-benzophenone tetracarboxylate, dimethyl 3,3',4,4'-diphenyl ether tetracarboxylate, diethyl 3,3',4,4'-diphenyl ether tetracarboxylate, dimethyl 3,3',4,4'-biphenyl sulfone tetracarboxylate or diethyl 3,3',4,4'-biphenyl sulfone tetracarboxylate;

[0047] The polar solvent is a mixture of one or more of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone or dimethyl sulfoxide.

[0048] The catalyst is a mixture of one or more of triethanolamine, triethylenediamine, stannous octoate, dibutyltin dilaurate or Dabco33-LV;

[0049] The foam stabilizer is a mixture of one or more of non-hydrolyzable water-soluble polyether siloxane, non-ionic fluorocarbon compound or polyethylene oxide;

[0050] The foaming agent is water;

[0051] The isocyanate is a mixture of one or more of diphenylmethane diisocyanate, xylene isocyanate or polyphenyl polymethylene polyisocyanate.

[0052] In step (1), the temperature of the foaming white material is maintained between 0-15°C; in step (2), the temperature of the isocyanate is maintained between 0-15°C.

[0053] The high temperature curing in step (4) is to place the polyimide foam intermediate compounded with the foamed aluminum into a high temperature forced air drying oven at 140-220° C. and heat for 0.5-3 hours.

[0054] A polyimide-aluminum heat-insulating and sound-absorbing composite foam is prepared by the above-mentioned preparation method of the polyimide-aluminum composite foam.

[0055] The thermal conductivity of polyimide-aluminum heat insulation and sound absorption composite foam is 0.070-0.085W / m·K, the starting sound absorption frequency point is 400-700Hz, and the density is 287-370kg / m 3 .

[0056] Example 2

[0057] Weigh 40 g of 40% solid content 3,3',4,4'-dimethylbenzophenone tetracarboxylate N,N-dimethylformamide solution, 2 g triethanolamine, 0.4 g dibutyltin dilaurate, Dabco33-LV 0.8 g, 10 g of a foam stabilizer obtained by mixing polyethylene glycol 600 and polyether siloxane foam stabilizer AK8805 in a mass ratio of 1:1, and 4.8 g of deionized water in a plastic cup, stir evenly with a glass rod to obtain a foaming white material, and then store it in a 10-degree Celsius constant temperature box for use; accurately weigh 60 g of zero-degree Celsius polymethylene polyphenyl polyisocyanate and pour it into the above foaming white material, stir it with a mechanical stirring paddle at a speed of 1000 rpm for 25 seconds to obtain a foaming slurry; quickly pour 50% of the foaming slurry into an upper-opening circular steel experimental mold with an inner cavity size of R=6 cm and H=20 cm; then pre-cut a density of 300 kg / m 3 , a cylindrical open-cell aluminum foam with a diameter of 10 cm and a thickness of 10 mm is quickly placed on the slurry, and then the remaining foaming slurry is poured on the open-cell aluminum foam; after standing for 5 minutes, the foaming slurry completes the foaming molding process and the filling of the aluminum foam in the mold to obtain the aluminum foam filled with polyimide foam intermediate; take out the aluminum foam filled with polyimide foam intermediate, and immediately put it into a high-temperature forced air drying oven at 180 degrees Celsius, and heat it for 2 hours to obtain the aluminum foam filled with polyimide foam.

[0058] After testing, the properties of the lightweight heat-insulating and sound-absorbing polyimide-aluminum composite foam material prepared in Example 2 are as follows:

[0059] Compared with pure foam aluminum, its thermal conductivity is reduced to 0.076W / (m·K); the sound absorption frequency range is widened to 2.33kHz at low frequencies, the starting sound absorption frequency is as low as 576Hz, and the average sound absorption coefficient in the widened frequency band is 0.46; the average sound absorption coefficient of pure foam aluminum starting sound absorption frequency point 2.9kHz to 6.4KHz is 0.63, and the average sound absorption coefficient of polyimide-aluminum composite foam in the above frequency band is 0.72; at the same time, the density of the filled polyimide foam is 18kg / m 3 ; The density of polyimide-aluminum composite foam material is 318kg / m 3 Compared with pure aluminum foam, the density of polyimide-aluminum composite foam is only increased by 18kg / m 3 , that is 6%.

[0060] Example 3

[0061] Referring to Example 2, the difference between this example and Example 2 is that 15 grams of polyether siloxane foam stabilizer L580 and 7.2 grams of deionized water are weighed, and the density of pure foam aluminum is 320 kg / m 3 , the rest is the same as Example 2.

[0062] The properties of the heat-insulating and sound-absorbing polyimide-aluminum composite foam material prepared in this embodiment are as follows:

[0063] Compared with pure foam aluminum, its thermal conductivity drops to 0.078W / (m·K); the starting sound absorption frequency point is 632Hz, the sound absorption frequency range is widened to the low frequency by 2.6kHz, and the average sound absorption coefficient in the widened frequency band is 0.51; the average sound absorption coefficient of pure foam aluminum starting sound absorption frequency point is 3.2kHz to 6.4KHz, and the average sound absorption coefficient of polyimide-aluminum composite foam in the above frequency band is 0.74; at the same time, the density of the filled polyimide foam is 10kg / m 3 ; The density of polyimide-aluminum composite foam material is 330kg / m 3 Compared with pure aluminum foam, the density of polyimide-aluminum composite foam is only increased by 10kg / m 3 , that is 3%.

[0064] Example 4

[0065] Referring to Example 2, the difference between this example and Example 2 is that the weight of various raw materials for preparing the foaming slurry is half of that in Example 2, and the density of pure foam aluminum is 330 kg / m 3 , the rest is the same as Example 2.

[0066] The properties of the heat-insulating and sound-absorbing polyimide-aluminum composite foam material prepared in this embodiment are as follows: compared with pure foam aluminum, its thermal conductivity is reduced to 0.081W / (m·K); the starting sound absorption frequency point is 596Hz, the sound absorption frequency range is widened to the low frequency by 2.5kHz, and the average sound absorption coefficient in the widened frequency band is 0.47; the average sound absorption coefficient of the starting sound absorption frequency point of pure foam aluminum from 3.1kHz to 6.4KHz is 0.62, and the average sound absorption coefficient of the polyimide-aluminum composite foam in the above frequency band is 0.74; at the same time, the density of the filled polyimide foam is 17kg / m 3 ; The density of polyimide-aluminum composite foam material is 347kg / m 3 Compared with pure aluminum foam, the density of polyimide-aluminum composite foam is only increased by 17kg / m 3 , or 5.2%.

[0067] It should be understood that the purpose of these embodiments is only to illustrate the present invention and is not intended to limit the protection scope of the present invention. In addition, it should also be understood that after reading the technical content of the present invention, those skilled in the art can make various changes, modifications and / or variations to the present invention, and all of these equivalent forms also fall within the protection scope defined by the appended claims of this application.

Claims

1. A method for preparing a polyimide-aluminum heat-insulating and sound-absorbing composite foam, characterized in that: The following steps are involved: (1) mixing a solution of an aromatic anhydride derivative dissolved in a polar solvent, a catalyst, a foam stabilizer and a foaming agent to obtain a foaming white material; (2) adding isocyanate to the foaming white material and mixing to obtain a foaming slurry; (3) First, pour 50-70% of the foaming slurry into an open mold, then press the open-cell foamed aluminum into the foaming slurry, and finally pour the remaining foaming slurry evenly into the mold. The foaming slurry is foamed and formed in the mold, and after standing, a foamed aluminum composited with a polyimide foam intermediate is obtained; (4) taking out the aluminum foam composited with the polyimide foam intermediate, and curing the aluminum foam composited with the polyimide foam intermediate at high temperature to obtain a polyimide-aluminum heat-insulating and sound-absorbing composite foam; The weight ratio of the aromatic anhydride derivative solution dissolved in the polar solvent, the catalyst, the foam stabilizer, the foaming agent and the isocyanate is 50-100:4-8:12-24:6-12:75-150; The solid content of the aromatic anhydride derivative solution is 20%-85%; The bottom area of ​​the open-cell aluminum foam is 64%-81% of the bottom area of ​​the mold cavity, and the thickness of the open-cell aluminum foam is 5%-10% of the mold depth; the mass ratio of the foaming slurry to the volume of the mold cavity is: 0.01-0.10g / cm 3 ; The density of open-cell aluminum foam is 280-350kg / m 3 ; The density of the polyimide foam intermediate in step (3) is 7-20 kg / m 3 .

2. The method for preparing a polyimide-aluminum heat-insulating and sound-absorbing composite foam according to claim 1, characterized in that: The aromatic anhydride derivative is a mixture of one or more of dimethyl pyromellitic acid, diethyl pyromellitic acid, dimethyl 3,3',4,4'-benzophenone tetracarboxylate, diethyl 3,3',4,4'-benzophenone tetracarboxylate, dimethyl 3,3',4,4'-diphenyl ether tetracarboxylate, diethyl 3,3',4,4'-diphenyl ether tetracarboxylate, dimethyl 3,3',4,4'-biphenyl sulfone tetracarboxylate or diethyl 3,3',4,4'-biphenyl sulfone tetracarboxylate; The polar solvent is a mixture of one or more of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone or dimethyl sulfoxide.

3. The method for preparing a polyimide-aluminum heat-insulating and sound-absorbing composite foam according to claim 1, characterized in that: The catalyst is a mixture of one or more of triethanolamine, triethylenediamine, stannous octoate, dibutyltin dilaurate or Dabco33-LV; The foam stabilizer is a mixture of one or more of non-hydrolyzable water-soluble polyether siloxane, non-ionic fluorocarbon compound or polyethylene oxide; The foaming agent is water; The isocyanate is a mixture of one or more of diphenylmethane diisocyanate, xylene isocyanate or polyphenyl polymethylene polyisocyanate.

4. The method for preparing a polyimide-aluminum heat-insulating and sound-absorbing composite foam according to claim 1, characterized in that: In step (1), the temperature of the foaming white material is maintained between 0-15°C; in step (2), the temperature of the isocyanate is maintained between 0-15°C.

5. The method for preparing the polyimide-aluminum heat-insulating and sound-absorbing composite foam according to claim 1, characterized in that: The high temperature curing in step (4) is to place the polyimide foam intermediate compounded with the foamed aluminum into a high temperature forced air drying oven at 140-220° C. and heat for 0.5-3 hours.

6. A polyimide-aluminum heat-insulating and sound-absorbing composite foam, characterized in that: The polyimide-aluminum composite foam is prepared by the preparation method of the polyimide-aluminum composite foam described in any one of claims 1 to 5.

7. The polyimide-aluminum heat-insulating and sound-absorbing composite foam according to claim 6, characterized in that: The thermal conductivity of polyimide-aluminum heat insulation and sound absorption composite foam is 0.070-0.085W / m·K, the starting sound absorption frequency point is 400-700Hz, and the density is 287-370kg / m 3 .

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