Heat-insulating polyimide foam material as well as preparation method and application thereof

Abstract

The invention discloses a thermal insulation polyimide foam material and a preparation method and application thereof, the preparation method comprises the following steps: (1) reacting a mixture I containing aromatic dianhydride, an alcoholic solution and a solvent I to obtain a first solution; (2) reacting a mixture II containing the first solution and aromatic diamine to obtain a second solution; (3) reacting a mixture III containing a surfactant, a second solution and water to obtain precursor powder; and (4) placing the precursor powder in a mold, and carrying out stepped microwave foaming molding and curing to obtain the heat-insulating polyimide foam material. The polyimide foam disclosed by the invention, as a light and high-temperature-resistant material, has a good application prospect in a light and extreme environment.

Description

Technical Field

[0001] The present application relates to a heat-insulating polyimide foam material, a preparation method and an application thereof, and belongs to the technical field of polyimide foam materials. Background Art

[0002] Polyimide foam material is a type of lightweight, porous polymer material with an imide ring in the main chain. It has excellent characteristics such as high and low temperature resistance, radiation resistance, flame retardancy, heat insulation, and noise reduction. It has received widespread attention from all walks of life. It is used as a thermal insulation material in ships, and as a wave-transparent material and lightweight support material in spacecraft. It has been widely used in aerospace, ocean shipping, automobiles, high-speed rail, microelectronics and other fields.

[0003] With the development of high-tech fields, higher performance requirements are being placed on polyimide foam materials. Currently, two main methods are used to produce polyimide foam: one is to react isocyanate with dianhydride to directly foam the product; the other is a powder foaming method, which starts with dianhydride and diamine monomers, first undergoing a polycondensation reaction to produce a polyester ammonium salt precursor powder. This powder is then filled into a mold and heated to foam the foamed product. The polyimide foams currently produced by both methods suffer from uneven cell structure, high density, and poor thermal insulation properties, which restrict their application. Therefore, it is crucial to improve the foaming process, prepare high-performance polyimide foam materials, enhance their thermal insulation properties, and reduce their density. Summary of the Invention

[0004] The present invention provides a thermally insulating polyimide foam, its preparation method, and its application. The novel thermally insulating polyimide foam material provided by the present invention utilizes microwave-assisted foaming, ensuring a low density while also achieving superior thermal insulation properties. Furthermore, the preparation process is simple and easy to control, facilitating large-scale production and application.

[0005] The invention provides a heat-insulating polyimide foam material. The heat-insulating polyimide foam material is prepared by a microwave-assisted thermal foaming method; the heat-insulating polyimide foam material has a porous structure.

[0006] According to one aspect of the present application, a method for preparing a thermal insulating polyimide foam material is provided, the method comprising the following steps:

[0007] (1) reacting a mixture I containing an aromatic dianhydride, an alcohol solution, and a solvent to obtain a first solution;

[0008] (2) reacting a mixture II containing the first solution and the aromatic diamine to obtain a second solution;

[0009] (3) reacting a mixture III containing a surfactant, a second solution, and water to obtain a precursor powder;

[0010] (4) The precursor powder is placed in a mold and subjected to gradient microwave foaming and curing to obtain the thermal insulating polyimide foam material.

[0011] Optionally, in step (4), the gradient microwave foaming includes a first microwave section, a second microwave section, and a third microwave section.

[0012] Optionally, the power of the first microwave section is 50-150 W, and the foaming time of the first microwave section is 5-20 min.

[0013] Optionally, the power of the second microwave section is 300-500W, and the foaming time of the second microwave section is 10-40 minutes.

[0014] Optionally, the power of the third microwave band is 600-900 W, and the foaming time of the third microwave band is 10-40 min.

[0015] Optionally, the amount of raw materials used for the thermal insulation polyimide foam material includes, by molar fraction of raw materials:

[0016]

[0017] Optionally, the aromatic dianhydride is selected from at least one of BTDA, PMDA, BPDA, ODPA, BPADA, and DSDA.

[0018] Optionally, the aromatic diamine is selected from at least one of 4,4'-ODA, p-PDA, BAPP, TPE-Q, TPE-R, MDA, BAPB, APBIA, APBOA, DMBZ, and 3,4'-ODA.

[0019] Optionally, the alcohol in the alcohol solution is selected from ethanol and / or methanol;

[0020] Optionally, in step (1), the solvent is tetrahydrofuran.

[0021] Optionally, the surfactant is water-soluble silicone oil.

[0022] Optionally, the water-soluble silicone oil is selected from at least one of polyether-modified organosiloxane and hydrophilic-modified organosilicon polymer DC-193.

[0023] Optionally, in step (4), the curing temperature is 240-300° C., and the curing time is 2-5 hours.

[0024] Optionally, in step (4), the upper limit of the curing temperature is independently selected from 300°C, 290°C, 280°C, 270°C, 260°C, and 250°C, and the lower limit is independently selected from 240°C, 250°C, 260°C, 270°C, 280°C, and 290°C.

[0025] Optionally, in step (1), the temperature of reaction I is 60-80° C., and the time of reaction I is 1-3 h.

[0026] Optionally, in step (1), the upper limit of the temperature of the reaction I is independently selected from 80°C, 78°C, 75°C, 70°C, and 65°C, and the lower limit is independently selected from 60°C, 65°C, 70°C, 75°C, and 78°C.

[0027] Optionally, in step (1), the upper limit of the time of reaction I is independently selected from 3 h, 2.5 h, 2 h, and 1.5 h, and the lower limit is independently selected from 1 h, 1.5 h, 2 h, and 2.5 h.

[0028] Optionally, in step (2), the temperature of reaction II is 60-80° C., and the time of reaction II is 5-12 h.

[0029] Optionally, in step (2), the upper limit of the temperature of reaction II is independently selected from 80°C, 78°C, 75°C, 70°C, and 65°C, and the lower limit is independently selected from 60°C, 65°C, 70°C, 75°C, and 78°C.

[0030] Optionally, in step (2), the upper limit of the time of reaction II is independently selected from 12h, 11h, 10h, 9h, 8h, 7h, 6h, and 5h, and the lower limit is independently selected from 5h, 6h, 7h, 8h, 9h, 10h, and 11h.

[0031] Optionally, in step (3), the temperature of reaction III is 20-50° C., and the time of reaction III is 0.5-2 h.

[0032] Optionally, in step (3), the upper limit of the temperature of reaction III is independently selected from 50°C, 45°C, 40°C, 35°C, 30°C, and 25°C, and the lower limit is independently selected from 20°C, 25°C, 30°C, 35°C, 40°C, and 45°C.

[0033] Optionally, in step (3), the upper limit of the time of reaction III is independently selected from 2h, 1.8h, 1.5h, 1.2h, and 1h, and the lower limit is independently selected from 0.5h, 1h, 1.2h, 1.5h, and 1.8h.

[0034] Optionally, in step (3), the particle size of the precursor powder is 70 to 150 μm.

[0035] Optionally, in step (3), the particle size of the precursor powder is independently selected from any value of 70um, 80um, 90um, 100um, 110um, 120um, 130um, 140um, 150um or a range between any two of the above values.

[0036] Optionally, the remaining solvent in the reaction III includes an alcohol solution, water and tetrahydrofuran.

[0037] Optionally, the content of the remaining solvent is 5% to 20%.

[0038] According to another aspect of the present application, a thermal insulating polyimide foam material prepared by the above-mentioned preparation method is provided, wherein the thermal conductivity of the thermal insulating polyimide foam material is 0.029 to 0.034 W / (m·K).

[0039] Optionally, the thermal conductivity of the insulating polyimide foam material is independently selected from any value among 0.029W / (m·K), 0.030W / (m·K), 0.031W / (m·K), 0.032W / (m·K), 0.033W / (m·K), 0.034W / (m·K) or a range between any two of the above values.

[0040] Optionally, the density of the thermal insulation polyimide foam material is 9 to 15 kg / m 3 .

[0041] Optionally, the density of the thermal insulating polyimide foam material is independently selected from 9 kg / m 3 、10kg / m 3 , 11kg / m 3 , 12kg / m 3 , 13kg / m 3 , 14kg / m 3 , 15kg / m 3 Any value in or a range of values ​​between any two of the above.

[0042] Optionally, the open cell ratio of the thermal insulation polyimide foam material is 80% to 98%.

[0043] Optionally, the open porosity of the thermal insulating polyimide foam material is independently selected from any value among 80%, 82%, 85%, 88%, 90%, 92%, 95%, 98% or a range between any two of the above values.

[0044] Optionally, the pore diameter of the thermal insulation polyimide foam material is 500-800 um.

[0045] Optionally, the pore diameter of the thermal insulation polyimide foam material is independently selected from any value among 500um, 550um, 600um, 650um, 700um, 750um, 800um, or a range between any two of the above values.

[0046] According to another aspect of the present application, there is provided an application of the above-mentioned thermal insulating polyimide foam material in the fields of aerospace, new energy vehicles, rail transportation, and ships.

[0047] As an optional implementation method, the present application is implemented through the following technical solutions:

[0048] The preparation method of the thermal insulation polyimide foam material comprises the following steps:

[0049] 1) mixing an aromatic dianhydride, a solvent, and an alcohol solution, and subjecting the mixture to a reflux reaction to obtain a first solution; mixing an aromatic diamine with the first solution, and subjecting the mixture to a polycondensation reaction to obtain a second solution; adding a surfactant and water to the second solution, and subjecting the mixture to a third solution; and subjecting the third solution to a solvent-reduced distillation under reduced pressure to obtain a precursor powder;

[0050] 2) The foaming precursor powder obtained in the above steps is placed in a mold and subjected to gradient microwave foaming molding, and finally heated and cured to obtain a thermal insulating polyimide foam material.

[0051] Optionally, the precursor powder has a particle size of 70 to 150 μm; the solvent residue includes tetrahydrofuran, alcohol solution and water; and the solvent content is 5% to 20%.

[0052] The present invention adopts a powder foaming method, through microwave foaming and heating to set the shape, to prepare polyimide foam. By controlling the amount of solvent and surfactant used in the precursor powder, the foaming ratio of the polyimide foam can be adjusted, and the density of the polyimide foam can be reduced to 9-15 kg / m 3 , with a thermal conductivity as low as 0.029-0.034 W / (m·K). Polyimide foam prepared by microwave-assisted thermal foaming combines low density with excellent thermal insulation properties. Furthermore, the preparation process is simple and easy to control, facilitating industrial-scale production and application. As a lightweight, high-temperature-resistant material, the polyimide foam of the present invention has promising application prospects in lightweight, extreme environments.

[0053] In this application, the compounds corresponding to the English names are as follows:

[0054] BTDA: 3,3',4,4'-benzophenonetetracarboxylic dianhydride;

[0055] PMDA: pyromellitic dianhydride;

[0056] BPDA: 3,3',4,4'-biphenyltetracarboxylic dianhydride;

[0057] ODPA: 4,4'-oxydiphthalic anhydride;

[0058] BPADA: 4,4'-(4,4'-isopropyldiphenoxy)bis(phthalic anhydride);

[0059] DSDA: 3,3,4,4-diphenylsulfonetetracarboxylic dianhydride;

[0060] 4,4'-ODA: 4,4'-diaminodiphenyl ether;

[0061] p-PDA: p-phenylenediamine;

[0062] BAPP: 2,2'-bis[4-(4-aminophenoxyphenyl)]propane;

[0063] TPE-Q: 1,4-bis(4-aminophenoxy)benzene;

[0064] TPE-R: 1,3-bis(4'-aminophenoxy)benzene;

[0065] MDA: 4,4'-methylenediaminodiphenylmethane;

[0066] BAPB: 4,4'-bis(4-aminophenoxy)biphenyl;

[0067] APBIA: 2-(4-aminophenyl)-5-aminobenzimidazole;

[0068] APBOA: 2-(4-aminophenyl)-5-aminobenzoxazole;

[0069] DMBZ: 2,2'-dimethyl-4,4'-diaminobenzidine;

[0070] 3,4'-ODA: 3,4'-diaminodiphenyl ether;

[0071] DC-193: Dow Corning water-soluble silicone oil.

[0072] The beneficial effects of this application include:

[0073] 1) The heat-insulating polyimide foam material provided in this application is commercially available as raw material, aromatic dianhydride and aromatic diamine monomers, at a low price. The microwave-assisted powder foaming method for preparing the polyimide foam is simple, with controllable conditions, and is easy to prepare on a large scale.

[0074] 2) The thermal insulation polyimide foam material provided by the present application, the experimental results show that the thermal insulation polyimide foam material prepared by the present invention has a density of 9.8kg / m 3The compressive strength is 16.3kPa at 30% strain, the compression recovery rate is 95%, and the thermal conductivity is 0.029W / (m·K). It has excellent comprehensive performance and outstanding thermal insulation performance.

[0075] 3) The polyimide foam material prepared by microwave-assisted foaming provided in this application has low density and excellent thermal insulation performance, and can be used as a high-performance thermal insulation foam material that is resistant to high temperatures in extreme environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0076] Figure 1 This is a pore morphology diagram of the thermal insulating polyimide foam material prepared in Example 1 of the present application.

[0077] Figure 2 This is a pore morphology diagram of the thermal insulating polyimide foam material prepared in Example 7 of the present application.

[0078] Figure 3 This is a pore morphology diagram of the thermal insulating polyimide foam material prepared in Example 10 of the present application. DETAILED DESCRIPTION

[0079] The present application is described in detail below with reference to embodiments, but the present application is not limited to these embodiments.

[0080] Unless otherwise specified, the raw materials in the examples of this application were purchased through commercial channels.

[0081] The methods described are all conventional methods unless otherwise specified.

[0082] This application uses the SEM6900 instrument of Zhongke Instrument for scanning electron microscopy characterization.

[0083] Example 1 Preparation of polyimide foam PI (BTDA-ODA)

[0084] 3,3',4,4'-Benzophenonetetracarboxylic dianhydride (BTDA) (16.1 g, 0.05 mol, 1.0 equiv) was weighed and added to a 500 mL three-necked flask. Tetrahydrofuran (100 mL) and anhydrous ethanol (50 mL) were then added. The mixture was heated to 70°C and refluxed with stirring for 2 hours. After cooling to 50°C, 4,4'-diaminodiphenyl ether (ODA) (10.0 g, 0.05 mol, 1.0 equiv) was added and refluxed for 6 hours. The mixture was cooled to room temperature, and DC-193 (0.2 g) and water (2 mL) were added. The mixture was stirred at room temperature for 30 minutes, and the solvent was removed by rotary evaporation. The mixture was then pulverized and sieved. The residual solvent consisted of ethanol, water, and tetrahydrofuran, with a solvent content of 15%. The resulting yellow powder, the precursor powder, had a particle size of 100 μm.

[0085] The precursor powder (10.0 g) was added to a mold and then placed in a microwave oven. The reaction was carried out at a power of 100 W for 10 minutes, 400 W for 10 minutes, and 600 W for 10 minutes. The mold was then transferred to a muffle furnace and heated to 270°C for 2 hours. The resulting foam was dark brown in color with a pore size of 505 μm and an open porosity of 98%. Figure 1 As shown, from Figure 1 It can be seen that the foam has a uniform cell structure.

[0086] Example 2 Preparation of polyimide foam PI (BTDA-ODA)

[0087] 3,3',4,4'-Benzophenonetetracarboxylic dianhydride (BTDA) (16.1 g, 0.05 mol, 1.0 equiv) was weighed and added to a 500 mL three-necked flask. Tetrahydrofuran (100 mL) and anhydrous ethanol (50 mL) were then added. The mixture was heated to 70°C and refluxed with stirring for 2 hours. After cooling to 50°C, 4,4'-diaminodiphenyl ether (ODA) (10.0 g, 0.05 mol, 1.0 equiv) was added and refluxed for 6 hours. The mixture was cooled to room temperature, and DC-193 (0.1 g) and water (3 mL) were added. The mixture was stirred at room temperature for 30 minutes, and the solvent was removed by rotary evaporation. The mixture was then pulverized and sieved. The residual solvent consisted of ethanol, water, and tetrahydrofuran, with a solvent content of 5%. The resulting precursor was a yellow powder with a particle size of 80 μm.

[0088] The precursor powder (10.0 g) was added to a mold and then placed in a microwave converter, reacted at a power of 100 W for 10 minutes, at 300 W for 10 minutes, and at 600 W for 15 minutes, and then transferred to a muffle furnace and heated to 270°C and kept warm for 2 hours to finally obtain a dark brown foam material with a pore size of 640 μm and an open porosity of 92%.

[0089] Example 3 Preparation of polyimide foam PI (BTDA-ODA)

[0090] 3,3',4,4'-Benzophenonetetracarboxylic dianhydride (BTDA) (16.1 g, 0.05 mol, 1.0 equiv) was weighed and added to a 500 mL three-necked flask. Tetrahydrofuran (100 mL) and anhydrous methanol (50 mL) were then added. The mixture was heated to 70°C and refluxed with stirring for 2 hours. After cooling to 50°C, 4,4'-diaminodiphenyl ether (ODA) (10.0 g, 0.05 mol, 1.0 equiv) was added and refluxed for 6 hours. The mixture was cooled to room temperature, and DC-193 (0.2 g) and water (3 mL) were added. The mixture was stirred at room temperature for 30 minutes, and the solvent was removed by rotary evaporation. The mixture was then pulverized and sieved. The residual solvent consisted of methanol, water, and tetrahydrofuran, with a solvent content of 10%. The resulting precursor was a yellow powder with a particle size of 110 μm.

[0091] The precursor powder (10.0 g) was added to the mold and then placed in a microwave converter, reacted at a power of 50 W for 10 minutes, at 400 W for 30 minutes, and at 800 W for 10 minutes, and then transferred to a muffle furnace and heated to 270°C and kept warm for 2 hours to finally obtain a dark brown foam material with a pore size of 510 μm and an open porosity of 90%.

[0092] Example 4 Preparation of polyimide foam PI (ODPA-ODA)

[0093] 4,4'-Oxydiphthalic anhydride (ODPA) (15.5 g, 0.05 mol, 1.0 equiv) was weighed and added to a 500 mL three-necked flask. Tetrahydrofuran (100 mL) and anhydrous ethanol (50 mL) were then added. The mixture was heated to 70°C and refluxed with stirring for 2 hours. After cooling to 50°C, 4,4'-diaminodiphenyl ether (ODA) (10.0 g, 0.05 mol, 1.0 equiv) was added and refluxed for 6 hours. The mixture was cooled to room temperature, and DC-193 (0.2 g) and water (2 mL) were added. The mixture was stirred at room temperature for 30 minutes, and the solvent was removed by rotary evaporation. The mixture was then pulverized and sieved. The residual solvent consisted of ethanol, water, and tetrahydrofuran, with a solvent content of 14%. The resulting precursor was a yellow powder with a particle size of 108 μm.

[0094] The precursor powder (10.0 g) was added to a mold and then placed in a microwave converter, reacted at a power of 100 W for 20 minutes, at 400 W for 15 minutes, and at 600 W for 20 minutes. The mixture was then transferred to a muffle furnace and heated to 270°C and kept warm for 2 hours to obtain a dark brown foam material with a pore size of 540 μm and an open porosity of 94%.

[0095] Example 5 Preparation of polyimide foam PI (ODPA-ODA)

[0096] 4,4'-Oxydiphthalic anhydride (ODPA) (15.5 g, 0.05 mol, 1.0 equiv) was weighed and added to a 500 mL three-necked flask. Tetrahydrofuran (100 mL) and anhydrous methanol (50 mL) were then added. The mixture was heated to 70°C and refluxed with stirring for 2 hours. After cooling to 50°C, 4,4'-diaminodiphenyl ether (ODA) (10.0 g, 0.05 mol, 1.0 equiv) was added and refluxed for 6 hours. The mixture was cooled to room temperature, and DC-193 (0.2 g) and water (3 mL) were added. The mixture was stirred at room temperature for 30 minutes, and the solvent was removed by rotary evaporation. The mixture was then pulverized and sieved. The residual solvent consisted of methanol, water, and tetrahydrofuran, with a solvent content of 20%. The resulting precursor was a yellow powder with a particle size of 88 μm.

[0097] The precursor powder (10.0 g) was added to a mold and then placed in a microwave converter, reacted at a power of 150 W for 10 minutes, at 400 W for 10 minutes, and at 600 W for 10 minutes, respectively. The mixture was then transferred to a muffle furnace and heated to 270°C and kept warm for 2 hours to finally obtain a dark brown foam material with a pore size of 750 μm and an open porosity of 96%.

[0098] Example 6 Preparation of polyimide foam PI (ODPA-ODA)

[0099] 4,4'-Oxydiphthalic anhydride (ODPA) (15.5 g, 0.05 mol, 1.0 equiv) was weighed and added to a 500 mL three-necked flask. Tetrahydrofuran (100 mL) and anhydrous methanol (50 mL) were then added. The mixture was heated to 70°C and refluxed with stirring for 2 hours. After cooling to 50°C, 4,4'-diaminodiphenyl ether (ODA) (10.0 g, 0.05 mol, 1.0 equiv) was added and refluxed for 6 hours. The mixture was cooled to room temperature, and DC-193 (0.1 g) and water (2.5 mL) were added. The mixture was stirred at room temperature for 30 minutes, and the solvent was removed by rotary evaporation. The mixture was then pulverized and sieved. The residual solvent consisted of methanol, water, and tetrahydrofuran, with a solvent content of 9%. The resulting yellow powder, the precursor powder, had a particle size of 110 μm.

[0100] The precursor powder (10.0 g) was added to a mold and then placed in a microwave converter, reacted at a power of 150 W for 15 minutes, at 400 W for 20 minutes, and at 800 W for 40 minutes. The mixture was then transferred to a muffle furnace and heated to 270°C and kept warm for 2 hours to obtain a dark brown foam material with a pore size of 690 μm and an open porosity of 97%.

[0101] Example 7 Preparation of polyimide foam PI (BTDA-MDA)

[0102] 3,3',4,4'-Benzophenonetetracarboxylic dianhydride (BTDA) (16.1 g, 0.05 mol, 1.0 equiv) was weighed and added to a 500 mL three-necked flask. Tetrahydrofuran (100 mL) and anhydrous ethanol (50 mL) were then added. The mixture was heated to 70°C and refluxed with stirring for 2 hours. After cooling to 50°C, 4,4'-methylenediaminodiphenylmethane (MDA) (9.9 g, 0.05 mol, 1.0 equiv) was added and the mixture was refluxed for 6 hours. The mixture was cooled to room temperature, and DC-193 (0.2 g) and water (2 mL) were added. The mixture was stirred at room temperature for 30 minutes, and the solvent was removed by rotary evaporation. The mixture was then pulverized and sieved. The residual solvent consisted of ethanol, water, and tetrahydrofuran, with a solvent content of 18%. The resulting yellow powder, the precursor powder, had a particle size of 110 μm.

[0103] The precursor powder (10.0 g) was added to a mold and then placed in a microwave oven. The reaction was carried out at a power of 50 W for 8 minutes, 400 W for 12 minutes, and 600 W for 10 minutes. The mold was then transferred to a muffle furnace and heated to 270°C for 2 hours. The resulting foam had a pore size of 780 μm and an open porosity of 98%. Figure 2 As shown, from Figure 2 It can be seen that the foam has a uniform cell structure.

[0104] Example 8 Preparation of polyimide foam PI (BTDA-MDA)

[0105] 3,3',4,4'-Benzophenonetetracarboxylic dianhydride (BTDA) (16.1 g, 0.05 mol, 1.0 equiv) was weighed and added to a 500 mL three-necked flask. Tetrahydrofuran (100 mL) and anhydrous methanol (50 mL) were then added. The mixture was heated to 70°C and refluxed with stirring for 2 hours. After cooling to 50°C, 4,4'-methylenediaminodiphenylmethane (MDA) (9.9 g, 0.05 mol, 1.0 equiv) was added and the mixture was refluxed for 6 hours. The mixture was cooled to room temperature, and DC-193 (0.1 g) and water (1.5 mL) were added. The mixture was stirred at room temperature for 30 minutes, and the solvent was removed by rotary evaporation. The mixture was then pulverized and sieved. The residual solvent consisted of methanol, water, and tetrahydrofuran, with a solvent content of 17%. The resulting yellow powder, the precursor powder, had a particle size of 80 μm.

[0106] The precursor powder (10.0 g) was added to a mold and then placed in a microwave converter, reacted at a power of 150 W for 5 minutes, at 400 W for 40 minutes, and at 800 W for 10 minutes. The mixture was then transferred to a muffle furnace and heated to 270°C and kept warm for 2 hours to obtain a dark brown foam material with a pore size of 660 μm and an open porosity of 97%.

[0107] Example 9 Preparation of polyimide foam PI (BTDA-MDA)

[0108] 3,3',4,4'-Benzophenonetetracarboxylic dianhydride (BTDA) (16.1 g, 0.05 mol, 1.0 equiv) was weighed and added to a 500 mL three-necked flask. Tetrahydrofuran (100 mL) and anhydrous methanol (50 mL) were then added. The mixture was heated to 70°C and refluxed with stirring for 2 hours. After cooling to 50°C, 4,4'-methylenediaminodiphenylmethane (MDA) (9.9 g, 0.05 mol, 1.0 equiv) was added and the mixture was refluxed for 6 hours. The mixture was cooled to room temperature, and DC-193 (0.1 g) and water (2 mL) were added. The mixture was stirred at room temperature for 30 minutes, and the solvent was removed by rotary evaporation. The mixture was then pulverized and sieved. The residual solvent consisted of methanol, water, and tetrahydrofuran, with a solvent content of 12%. The resulting yellow powder, the precursor powder, had a particle size of 88 μm.

[0109] The precursor powder (10.0 g) was added to a mold and then placed in a microwave converter, reacted at a power of 150 W for 10 minutes, 500 W for 10 minutes, and 800 W for 15 minutes, respectively. The mixture was then transferred to a muffle furnace and heated to 270°C and kept warm for 2 hours to finally obtain a dark brown foam material with a pore size of 680 μm and an open porosity of 94%.

[0110] Example 10 Preparation of polyimide foam PI (BTDA-DMBZ)

[0111] 3,3',4,4'-Benzophenonetetracarboxylic dianhydride (BTDA) (16.1 g, 0.05 mol, 1.0 equiv) was weighed and added to a 500 mL three-necked flask. Tetrahydrofuran (100 mL) and anhydrous methanol (50 mL) were then added. The mixture was heated to 70°C and refluxed with stirring for 2 hours. After cooling to 50°C, 2,2'-dimethyl-4,4'-diaminobiphenyl (DMBZ) (10.6 g, 0.05 mol, 1.0 equiv) was added and refluxed for 6 hours. The mixture was cooled to room temperature, and DC-193 (0.2 g) and water (2.5 mL) were added. The mixture was stirred at room temperature for 30 minutes, and the solvent was removed by rotary evaporation. The mixture was then pulverized and sieved. The residual solvent consisted of methanol, water, and tetrahydrofuran, with a solvent content of 15%. The resulting yellow powder, the precursor powder, had a particle size of 110 μm.

[0112] The precursor powder (10.0 g) was added to a mold and then placed in a microwave oven. The reaction was carried out at a power of 150 W for 10 minutes, 400 W for 15 minutes, and 800 W for 15 minutes. The mold was then transferred to a muffle furnace and heated to 270°C for 2 hours. The resulting foam had a pore size of 570 μm and an open porosity of 96%. Figure 3 As shown, from Figure 3 It can be seen that the foam has a uniform cell structure.

[0113] Example 11 Preparation of polyimide foam PI (BTDA-DMBZ)

[0114] 3,3',4,4'-Benzophenonetetracarboxylic dianhydride (BTDA) (16.1 g, 0.05 mol, 1.0 equiv) was weighed and added to a 500 mL three-necked flask. Tetrahydrofuran (100 mL) and anhydrous ethanol (50 mL) were then added. The mixture was heated to 70°C and refluxed with stirring for 2 hours. After cooling to 50°C, 2,2'-dimethyl-4,4'-diaminobiphenyl (DMBZ) (10.6 g, 0.05 mol, 1.0 equiv) was added and refluxed for 6 hours. The mixture was cooled to room temperature, and DC-193 (0.2 g) and water (2 mL) were added. The mixture was stirred at room temperature for 30 minutes, and the solvent was removed by rotary evaporation. The mixture was then pulverized and sieved. The residual solvent consisted of ethanol, water, and tetrahydrofuran, with a solvent content of 13%. The resulting yellow powder, the precursor powder, had a particle size of 110 μm.

[0115] The precursor powder (10.0 g) was added to a mold and then placed in a microwave converter, reacted at a power of 150 W for 10 minutes, at 500 W for 30 minutes, and at 900 W for 20 minutes. The mixture was then transferred to a muffle furnace and heated to 270°C and kept warm for 2 hours to obtain a dark brown foam material with a pore size of 680 μm and an open porosity of 84%.

[0116] Example 12 Preparation of polyimide foam PI (BTDA-DMBZ)

[0117] 3,3',4,4'-Benzophenonetetracarboxylic dianhydride (BTDA) (16.1 g, 0.05 mol, 1.0 equiv) was weighed and added to a 500 mL three-necked flask. Tetrahydrofuran (100 mL) and anhydrous ethanol (50 mL) were then added. The mixture was heated to 70°C and refluxed with stirring for 2 hours. After cooling to 50°C, 2,2'-dimethyl-4,4'-diaminobiphenyl (DMBZ) (10.6 g, 0.05 mol, 1.0 equiv) was added and refluxed for 6 hours. The mixture was cooled to room temperature, and DC-193 (0.3 g) and water (2 mL) were added. The mixture was stirred at room temperature for 30 minutes, and the solvent was removed by rotary evaporation. The mixture was then pulverized and sieved. The residual solvent consisted of ethanol, water, and tetrahydrofuran, with a solvent content of 17%. The resulting yellow powder, the precursor powder, had a particle size of 88 μm.

[0118] The precursor powder (10.0 g) was added to a mold and then placed in a microwave converter, reacted at a power of 150 W for 8 minutes, 500 W for 20 minutes, and 700 W for 30 minutes, and then transferred to a muffle furnace and heated to 270°C and kept warm for 2 hours to finally obtain a dark brown foam material with a pore size of 750 μm and an open porosity of 80%.

[0119] Comparative Example 1

[0120] Weigh 3,3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA) (16.1g, 0.05mol, 1.0equiv) into a 500mL three-necked flask, and add tetrahydrofuran (100mL) and anhydrous ethanol (50mL) respectively. The mixture is heated to 70℃ and refluxed with stirring for 2 hours. After cooling to 50℃, 4,4'-diaminodiphenyl ether (ODA) (10.0g, 0.05mol, 1.0equiv) is added and refluxed for 6 hours. Cool to room temperature, add DC-193 (0.2g) and water (2mL), stir at room temperature for 30 minutes, remove the solvent by rotary evaporation, crush, and sieve. The solvent residue is ethanol, water, and tetrahydrofuran, with a solvent content of 15%. Finally, a yellow powder, i.e., the precursor powder, is obtained with a particle size of 100μm.

[0121] The precursor powder (10.0 g) was added to a mold, and then placed in a microwave converter, and reacted at a power of 200 W for 10 minutes, 550 W for 10 minutes, and 950 W for 10 minutes, respectively. The foaming failed and no foamed material was obtained.

[0122] Comparative Example 2

[0123] Weigh 3,3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA) (16.1g, 0.05mol, 1.0equiv) into a 500mL three-necked flask, and add tetrahydrofuran (100mL) and anhydrous ethanol (50mL) respectively. The mixture is heated to 70℃ and refluxed with stirring for 2 hours. After cooling to 50℃, 4,4'-diaminodiphenyl ether (ODA) (10.0g, 0.05mol, 1.0equiv) is added and refluxed for 6 hours. Cool to room temperature, add DC-193 (0.2g) and water (2mL), stir at room temperature for 30 minutes, remove the solvent by rotary evaporation, crush, and sieve. The solvent residue is ethanol, water, and tetrahydrofuran, with a solvent content of 15%. Finally, a yellow powder, i.e., the precursor powder, is obtained with a particle size of 100μm.

[0124] The precursor powder (10.0 g) was added to a mold, and then placed in a microwave converter, and reacted at a power of 100 W for 25 minutes, 400 W for 45 minutes, and 600 W for 45 minutes, respectively. The foaming failed and no foamed material was obtained.

[0125] Test Example 1

[0126] The performance of the novel thermal insulation polyimide foam material prepared in the embodiment of the present invention was tested.

[0127] The density test standard is GB / T 6343-2009, the compressive strength test standard is GB / T8813-2008, and the thermal conductivity test standard is GB / T 10295-2008.

[0128] See Table 1, which shows the performance test results of the novel thermal insulation polyimide foam material prepared in the examples of the present invention.

[0129] Table 1. Properties of polyimide foam

[0130]

[0131] It can be seen from the data in Table 1 that the density of the polyimide foam material prepared by microwave assisted foaming is as low as 9.3 kg / m 3 The compression performance shows excellent compression recovery, the thermal conductivity is as low as 0.029W / (m·K), and the thermal insulation performance is good.

[0132] The above is a detailed introduction to the thermal insulation polyimide foam material provided by the present invention, its preparation method and application. Specific examples are used herein to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only intended to help understand the method and core ideas of the present invention, including the best mode, and also to enable any technician in the field to practice the present invention, including the manufacture and use of any device or system, and the implementation of any combined method. It should be noted that for ordinary technicians in this technical field, without departing from the principles of the present invention, several improvements and modifications can be made to the present invention, and these improvements and modifications also fall within the scope of protection of the claims of the present invention. The scope of patent protection of the present invention is defined by the claims and may include other embodiments that can be thought of by those skilled in the art. If these other embodiments have structural elements that are not different from the literal wording of the claims, or if they include equivalent structural elements that are not substantially different from the literal wording of the claims, then these other embodiments should also be included in the scope of the claims.

[0133] The above descriptions are merely a few embodiments of the present application and do not constitute any form of limitation to the present application. Although the present application discloses the preferred embodiments as above, they are not intended to limit the present application. Any technical personnel familiar with the present profession, without departing from the scope of the technical solution of the present application, using the technical content disclosed above to make slight changes or modifications are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A method for preparing a thermal insulating polyimide foam material, characterized in that: The preparation method comprises the following steps: (1) reacting a mixture I containing an aromatic dianhydride, an alcohol solution, and a solvent to obtain a first solution; (2) reacting a mixture II containing the first solution and the aromatic diamine to obtain a second solution; (3) reacting a mixture III containing a surfactant, a second solution, and water to obtain a precursor powder; (4) The precursor powder is placed in a mold and subjected to gradient microwave foaming and curing to obtain the thermal insulating polyimide foam material.

2. The preparation method according to claim 1, characterized in that In the step (4), the gradient microwave foaming includes a first microwave section, a second microwave section, and a third microwave section; Preferably, the power of the first microwave band is 50-150W, and the foaming time of the first microwave band is 5-20min; Preferably, the power of the second microwave range is 300-500W, and the foaming time of the second microwave range is 10-40min; Preferably, the power of the third microwave band is 600-900W, and the foaming time of the third microwave band is 10-40 minutes.

3. The preparation method according to claim 1, characterized in that Calculated by molar fraction of raw materials, the raw material usage of the thermal insulation polyimide foam material includes:

4. The preparation method according to claim 1, characterized in that The aromatic dianhydride is selected from at least one of BTDA, PMDA, BPDA, ODPA, BPADA, and DSDA; Preferably, the aromatic diamine is selected from at least one of 4,4'-ODA, p-PDA, BAPP, TPE-Q, TPE-R, MDA, BAPB, APBIA, APBOA, DMBZ, and 3,4'-ODA; Preferably, the alcohol in the alcohol solution is selected from ethanol and / or methanol; Preferably, in step (1), the solvent is tetrahydrofuran.

5. The preparation method according to claim 1, characterized in that The surfactant is water-soluble silicone oil; Preferably, the water-soluble silicone oil is selected from at least one of polyether-modified organosiloxane and hydrophilic-modified organosilicon polymer DC-193.

6. The preparation method according to claim 1, characterized in that In the step (4), the curing temperature is 240-300° C., and the curing time is 2-5 hours.

7. The preparation method according to claim 1, characterized in that In the step (1), the temperature of the reaction I is 60 to 80° C., and the reaction time is 1 to 3 hours; Preferably, in step (2), the temperature of reaction II is 60-80° C., and the time of reaction II is 5-12 h; Preferably, in step (3), the temperature of reaction III is 20-50° C., and the time of reaction III is 0.5-2 h; Preferably, in step (3), the particle size of the precursor powder is 70 to 150 μm; Preferably, the remaining solvent in the reaction III comprises an alcohol solution, water and tetrahydrofuran; Preferably, the content of the remaining solvent is 5% to 20%.

8. The thermal insulating polyimide foam material prepared by the preparation method according to any one of claims 1 to 7, characterized in that: The thermal conductivity of the heat-insulating polyimide foam material is 0.029 to 0.034 W / (m·K); Preferably, the density of the thermal insulation polyimide foam material is 9 to 15 kg / m 3 .

9. The heat-insulating polyimide foam material according to claim 8, characterized in that: The open cell rate of the thermal insulation polyimide foam material is 80% to 98%; Preferably, the pore diameter of the thermal insulation polyimide foam material is 500-800 μm.

10. Use of the thermal insulating polyimide foam material according to any one of claims 8 to 9 in the fields of aerospace, new energy vehicles, rail transportation, and ships.

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