Polyimide aerogel film, preparation method and application thereof, and polyimide aerogel film production system

Abstract

The invention relates to the technical field of aerogel materials, and discloses a polyimide aerogel film, a preparation method and application thereof, and a polyimide aerogel film production system, the thickness standard deviation of the polyimide aerogel film is less than or equal to 6%, and the 24-hour water absorption rate is 2-10 wt%. The polyimide aerogel film produced on a large scale is better in thickness uniformity and product quality stability, low in water absorption and excellent in hydrophobic performance.

Description

Technical Field

[0001] The present invention relates to the technical field of aerogel materials, and particularly relates to a polyimide aerogel film, a preparation method and application thereof, and a polyimide aerogel film production system. Background Art

[0002] Polyimide aerogel is an organic polymer porous material containing imide rings. Its main characteristics are integrating the advantages of polyimide materials such as high mechanical strength, good thermal stability, wear resistance, and aerogel-like nanoporous materials such as high specific surface area, high porosity, and low thermal conductivity. It can not only increase the diversity of polyimide materials and optimize their structural properties, but also make up for the shortcomings of silica or inorganic aerogels being brittle and unable to be used alone.

[0003] In recent years, some research has been done at home and abroad on the structural adjustment, functionalization, and application of polyimide aerogel gels; however, it has not been possible to obtain polyimide aerogel film products with stable quality, good hydrophobicity, good flexibility, low density, high tensile strength, and good dielectric properties under large-scale production conditions.

[0004] CN106832364A discloses a preparation method of a flexible cross-linked polyimide aerogel film. Using dianhydride and diamine as monomers to synthesize a polyamic acid solution, and using aminophenylsilsesquioxane as a cross-linking agent, a gel film can be continuously prepared through a chemical imidization process, and further using technologies such as supercritical drying to prepare a high-performance polyimide aerogel film. This prior art can prepare a polyimide aerogel film with low density, high strength, good heat insulation and insulation effects. However, during its forming process, it is coated on substrates such as polytetrafluoroethylene plates, glass plates, or stainless steel plates. In this process, one side is adhered to the substrate while the other side is exposed to the air, resulting in different surface properties of the formed aerogel film, and it is extremely easy to have problems of different shrinkages during subsequent drying, and the defect of low yield, which is not conducive to industrial production. Summary of the Invention

[0005] The purpose of the present invention is to solve the problems of unstable quality, uneven thickness, and high water absorption rate during the continuous large-scale production of polyimide aerogel films in the prior art.

[0006] To achieve the above purpose, the first aspect of the present invention provides a polyimide aerogel film, and the standard deviation of the thickness of this polyimide aerogel film ≤ 6%, and the water absorption rate in 24 hours is 2 - 10 wt%.

[0007] The second aspect of the present invention provides a method for preparing the polyimide aerogel film described in the first aspect above, and this method includes:

[0008] (1) In the presence of an organic solvent, a diamine monomer and a dianhydride monomer are subjected to a first reaction to obtain a mixture I;

[0009] The diamine monomer contains an amino group and a hydrophobic group, and the molar ratio of the amino group to the hydrophobic group is 0.5 - 1.67:1; the molar ratio of the amino group in the diamine monomer to the anhydride group in the dianhydride monomer is 1:0.93 - 1.07;

[0010] (2) The mixture I is subjected to a second reaction with a dehydrating agent and a catalyst to obtain a mixture II;

[0011] (3) The mixture II is successively subjected to defoaming, coating and forming, aging, solvent replacement, and supercritical drying to obtain the polyimide aerogel film.

[0012] The third aspect of the present invention provides an application of the polyimide aerogel film described in the first aspect in the fields of computers, communications, or consumer electronic products.

[0013] The fourth aspect of the present invention provides a polyimide aerogel film production system, which includes a batching unit, a defoaming unit, a coating and forming unit, an aging unit, a solvent replacement unit, and a supercritical drying unit;

[0014] Among them, the batching unit is used to sequentially introduce the raw materials for producing the polyimide aerogel film into a reaction kettle for mixing reaction to obtain a polyimide aerogel slurry I;

[0015] The defoaming unit is used to defoam the polyimide aerogel slurry I to obtain a polyimide aerogel slurry II;

[0016] The coating and forming unit includes a coating unit, a curing unit, and a winding unit; the coating unit is used to coat the polyimide aerogel slurry II between two layers of polymer auxiliary films to obtain a polyimide aerogel liquid film; the curing unit is used to cure the polyimide aerogel liquid film to obtain a polyimide aerogel solid film I; the winding unit is used to separate the polyimide aerogel solid film I and the two layers of polymer auxiliary films into three layers to obtain a polyimide aerogel solid film II;

[0017] The aging unit is kept airtight to allow the unreacted monomers in the polyimide aerogel solid film II to continue to react in an airtight environment to obtain a polyimide aerogel solid film III;

[0018] The solvent replacement unit is used to replace the solvent in the polyimide aerogel solid film III with a solvent capable of supercritical drying to obtain a polyimide aerogel solid film IV;

[0019] The supercritical drying unit is used to perform supercritical drying treatment on the polyimide aerogel solid film IV to obtain the polyimide aerogel film.

[0020] The technical solution provided by the present invention has at least the following advantages:

[0021] (1) The polyimide aerogel film provided by the present invention has better thickness uniformity and product quality stability in large-scale production, low water absorption rate, and excellent hydrophobic performance.

[0022] (2) The polyimide aerogel film provided by the present invention has a uniform structure and uniform molecular weight, a complete polyimide gel network structure, is not easy to collapse, has higher flexibility and strength, and has excellent mechanical properties.

[0023] (3) The polyimide aerogel film production system provided by the present invention can obtain polyimide aerogel film products with stable quality, good hydrophobicity, good flexibility, low density, high tensile strength, and good dielectric properties under the condition of large-scale production. Description of the Drawings

[0024] Figure 1 It is a schematic diagram of a polyimide aerogel film production system according to an alternative embodiment of the present invention. Detailed Embodiments

[0025] The endpoints and any values disclosed in the ranges in this article are not limited to the exact ranges or values. These ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed in this article.

[0026] As mentioned above, the first aspect of the present invention provides a polyimide aerogel film, and the standard deviation of the thickness of the polyimide aerogel film is ≤6%, preferably ≤5%, more preferably ≤4%; the water absorption rate in 24 hours is 2-10 wt%, preferably 2-8 wt%, more preferably 2-6 wt%.

[0027] The standard deviation of the thickness described in the present invention represents the thickness uniformity of the polyimide aerogel film material.

[0028] Preferably, the thermal conductivity of the polyimide aerogel film is 0.015-0.025 W / (m·k).

[0029] Preferably, the polyimide aerogel film has a dielectric constant of ≤1.5 at 10 GHz and a dielectric loss of ≤0.004 at 10 GHz. More preferably, the polyimide aerogel film has a dielectric constant of 1.0 - 1.3 at 10 GHz and a dielectric loss of 0.0001 - 0.002 at 10 GHz.

[0030] Preferably, the density of the polyimide aerogel film is 0.06 - 0.15 g / cm 3 .

[0031] Preferably, the tensile strength of the polyimide aerogel film is 1.5 - 5.0 MPa.

[0032] Preferably, the light transmittance of the polyimide aerogel film is ≥80%.

[0033] The polyimide aerogel film provided by the present invention has excellent mechanical properties. In some embodiments, the tensile strength of the polyimide aerogel film is 1 - 3 MPa. The tensile strength of the polyimide aerogel film provided by the present invention can be adjusted according to actual needs.

[0034] As described above, the second aspect of the present invention provides a method for preparing the polyimide aerogel film described in the first aspect above, and the method includes:

[0035] (1) In the presence of an organic solvent, a diamine monomer and a dianhydride monomer are subjected to a first reaction to obtain a mixture I;

[0036] The diamine monomer contains an amino group and a hydrophobic group, and the molar ratio of the amino group to the hydrophobic group is 0.5 - 1.67:1; the molar ratio of the amino group in the diamine monomer to the anhydride group in the dianhydride monomer is 1:0.93 - 1.07;

[0037] (2) The mixture I is subjected to a second reaction with a dehydrating agent and a catalyst to obtain a mixture II;

[0038] (3) The mixture II is successively subjected to defoaming, coating and forming, aging, solvent replacement and supercritical drying to obtain the polyimide aerogel film.

[0039] The "hydrophobic group" as used in the present invention refers to a group that has no affinity for water and is insoluble in water or has extremely low solubility in water. According to a preferred embodiment of the present invention, the hydrophobic group is selected from at least one of -CH3, -F, -CF3.

[0040] According to a preferred embodiment of the present invention, the method in step (1) further includes: in the presence of an organic solvent, the intermediate product obtained by subjecting the diamine monomer and the dianhydride monomer to the first reaction is contacted with a crosslinking agent for a reaction to obtain the mixture I.

[0041] Preferably, the crosslinking agent is selected from at least one of 1,3,5-tris(4-aminophenoxy)benzene, 1,3,5-benzenetricarbonyl trichloride, tris(2-aminoethyl)amine, octakis(aminophenyltrioxysilane), and tris(4-aminophenyl)benzene.

[0042] In some preferred embodiments of the present invention, in step (1), the diamine monomer is a combination of diamine I and diamine II, and the molar ratio of diamine I to diamine II is 0.1-2.5:1.

[0043] In some preferred embodiments of the present invention, the diamine monomer is diamine II.

[0044] In the present invention, diamine I is a diamine compound without a hydrophobic group, and diamine II is a diamine compound with a hydrophobic group.

[0045] Preferably, diamine I is selected from at least one of 4,4-diaminodiphenyl ether, p-phenylenediamine, m-phenylenediamine, benzidine, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenyl sulfone, 1,5-naphthalenediamine, 3,3'-dimethoxybenzidine, 4,4'-diaminobenzyl, 1,3-cyclohexanediamine, 1,2-ethylenediamine, 1,12-diaminododecane, 4,4'-bis(4-aminophenoxy)biphenyl, and 1,4-bis(4-aminophenoxy)benzene.

[0046] Preferably, diamine II is selected from at least one of 3,3'-dimethyl-4,4'-diaminobiphenyl, 2,2-bis(3-amino-4-tolyl)hexafluoropropane, 3,3'-dimethyl-4,4'-diaminodiphenylmethane, 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl, 4,4'-(hexafluoroisopropylidene)dianiline, 4,4'-diaminooctafluorobiphenyl, 2,2'-bis(trifluoromethyl)-4,4'-diaminophenyl ether, 1,3-bis[2-(4-aminophenyl)-2-propyl]benzene, 4,4'-[1,4-phenylene-bis(1-methylethylene)]bis(N-phenyl)aniline, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, polyetheramine, and 4,4'-diamino-2,2'-dimethylbiphenyl.

[0047] Preferably, in step (1), the organic solvent accounts for 75-95% of the total mass of mixture I.

[0048] Preferably, in step (1), the dianhydride monomer is selected from at least one of 3,3',4,4'-biphenyltetracarboxylic dianhydride, hexafluorodiacid dianhydride, pyromellitic dianhydride, diphenyl ether tetracarboxylic dianhydride, bisphenol A dianhydride, 3,3',4,4'-benzophenone tetracarboxylic dianhydride, 3,3,4,4-diphenylsulfone tetracarboxylic dianhydride, 9,9-bis(trifluoromethyl)xanthene tetracarboxylic dianhydride.

[0049] Preferably, in step (1), the organic solvent is selected from at least one of N-methylpyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide, dimethyl sulfoxide, diethyl sulfoxide, N-cyclohexyl-2-imidazolinone, diethylene glycol dimethyl ether, o-dichlorobenzene, acetonitrile, ethyl acetate, hexamethylphosphoramide, acetone.

[0050] Preferably, in step (2), the dehydrating agent is selected from at least one of acetic anhydride, propionic anhydride, n-butyric anhydride, hexanoic anhydride, benzoic anhydride, heptanoic anhydride, trifluoroacetic anhydride.

[0051] Preferably, in step (2), the catalyst is pyridine and / or triethylamine.

[0052] Preferably, in step (2), the molar ratio of the dehydrating agent to the catalyst is 1:0.8 - 1.2.

[0053] Preferably, the molar ratio of the dehydrating agent to the dianhydride monomer is 6 - 8:1.

[0054] According to a preferred embodiment of the present invention, in step (1), the conditions of the first reaction include: temperature is 18 - 25°C, time is 30 - 120 min.

[0055] According to a preferred embodiment of the present invention, in step (1), the conditions of the contact reaction include: temperature is 18 - 25°C, time is 4 - 10 min.

[0056] According to a preferred embodiment of the present invention, in step (2), the conditions of the second reaction include: temperature is 15 - 25°C, time is 1 - 10 min.

[0057] According to a preferred embodiment of the present invention, in step (3), the defoaming is carried out in a vacuum environment by centrifugal defoaming, and the vacuum degree of the vacuum environment is -0.08 to -0.1 MPa.

[0058] In the present invention, after all the required raw materials are added to the reaction system, the viscosity of the mixed system will increase rapidly and gradually form a gel. Therefore, it is necessary to complete defoaming within the operable time. The inventor found in the research that the centrifugal defoaming method can achieve rapid defoaming after the reaction ends and will not generate new bubbles, and a polyimide aerogel film with more excellent product quality can be prepared.

[0059] According to a preferred embodiment of the present invention, in step (3), the operation of coating and forming includes:

[0060] Introducing the material after the defoaming into the space between two polymer auxiliary films for the coating and forming; the polymer auxiliary film is obtained by coating silicone oil on the surface of a polymer film, and the side coated with silicone oil is in direct contact with the material after the defoaming.

[0061] Preferably, the polymer auxiliary film is coated with silicone oil on one side only.

[0062] In the present invention, a polymer auxiliary film coated with silicone oil on one side only is preferably used.

[0063] Preferably, the polymer film meets the conditions: the thickness is 50 - 150 μm.

[0064] Preferably, the polymer auxiliary film meets the conditions: the transparency is 75% - 95%, and the tensile strength is 50 - 150 MPa.

[0065] Preferably, the release force of the polymer auxiliary film is 15 - 50 g / cm.

[0066] According to a preferred embodiment of the present invention, the polymer film remains stable at a use temperature above 70°C and does not react with the organic solvents used in the present invention.

[0067] According to a preferred embodiment of the present invention, the polymer film is selected from at least one of PET film, PP film, PTFE film, PE film, PPS film, and PI film.

[0068] In the present invention, PET film refers to polyester film, PP film refers to polypropylene film, PTFE film refers to polytetrafluoroethylene film, PE film refers to polyethylene film, PPS film refers to polyphenylene sulfide film, and PI film refers to polyimide film.

[0069] The present invention does not particularly limit the specific type of the silicone oil, and those skilled in the art can select according to the known types of silicone oil in the art. Exemplarily, the silicone oil is a polysiloxane-based silicone oil, which can be methyl silicone oil, ethyl silicone oil, or phenyl silicone oil.

[0070] The present invention has no particular limitation on the specific operation of coating silicone oil on the polymer film. Those skilled in the art can select according to the known technical means in the art, or obtain the polymer auxiliary film through commercial purchase. The present invention will not elaborate herein, and those skilled in the art should not understand it as a limitation to the present invention.

[0071] By adopting the coating and forming operation under the preferred conditions provided by the present invention, first, it ensures the consistency and uniformity of the upper and lower surface structures of the polyimide (PI) aerogel; second, the PI aerogel film is located between two auxiliary films, which avoids the solvent volatilization caused by temperature after entering the curing line in the subsequent stage and affects the performance of the material; third, the PI aerogel film is located between two auxiliary films, which can effectively reduce the volatilization of organic solvents and create a good working environment; fourth, the polymer auxiliary film treated with silicone oil can enable the PI aerogel film to be well separated from the polymer auxiliary film, avoiding the tearing and thinning of the PI aerogel film caused by the adhesion between the PI aerogel film and the polymer auxiliary film; fifth, it avoids the direct contact between the PI liquid material and the doctor blade, thus preventing the material from sticking to the doctor blade. The material sticking to the doctor blade will gel within a certain period of time, and the gel sticking to the doctor blade will cause scratches and local non-uniformity on the liquid material when continuing the coating.

[0072] According to a preferred embodiment of the present invention, the coating and forming operation in step (3) includes:

[0073] S1: Introduce the defoamed material between two polymer auxiliary films, and perform coating using a doctor blade or roll pressing to obtain intermediate material I;

[0074] S2: Cure the intermediate material I. The curing treatment adopts a gradient heating method, and the temperature interval between adjacent gradients is 5 - 10 °C to obtain intermediate material II;

[0075] S3: Wind up the intermediate material II to separate the polyimide aerogel film from the two polymer auxiliary films.

[0076] According to a preferred embodiment of the present invention, the coating is carried out under the condition that the temperature is -8 °C to 20 °C, preferably -8 °C to 0 °C, and more preferably -6 °C to -4 °C.

[0077] Adopting the gradient heating method under the preferred conditions of the present invention can improve the microstructural uniformity of the polyimide aerogel film product and obtain a film product with more excellent mechanical properties and transparency.

[0078] In some embodiments, the winding is a non-tension winding. The non-tension winding refers to a winding method with a winding tension < 50 N / m, which can effectively reduce the stretching of the polyimide aerogel film, prevent it from being thinned, and at the same time maintain the stability of the winding.

[0079] The present invention does not impose any particular restrictions on the specific manner of achieving the tension-free winding. Those skilled in the art can select according to the known technical means in the art, and the present invention will not elaborate herein. Those skilled in the art should not construe this as a limitation to the present invention.

[0080] According to a preferred embodiment of the present invention, the aging is carried out under airtight conditions, with the aging temperature being 18 - 45°C, preferably 20 - 30°C; and the time being 5 - 24 h, preferably 10 - 20 h. By adopting the aging method under the preferred conditions of the present invention, on the one hand, the nano-porous structure can be maintained without collapsing due to the volatilization of organic solvents, resulting in a decline in product quality. On the other hand, the airtight container can effectively prevent the volatilization of organic solvents into the air, providing a good working environment for production.

[0081] According to a preferred embodiment of the present invention, absolute ethanol is used for the solvent replacement.

[0082] Currently, the polyimide aerogel mainly adopts the gradient replacement method. Otherwise, it is extremely easy to cause changes in the aerogel structure or even collapse. However, the polyimide aerogel film prepared by the technical solution provided by the present invention has a uniform structure and a uniform molecular weight, and the polyimide gel network structure is complete. The present invention can adopt the direct replacement method without causing changes in the aerogel structure, avoiding the generation of a large amount of mixed solvents, and facilitating the later solvent recovery and use. At the same time, the film material prepared by the present invention has a small thickness. Preferably, the thickness of the polyimide aerogel is 100 - 300 μm, and the solvent can enter the gel interior in a short time during replacement to complete the replacement.

[0083] According to a preferred embodiment of the present invention, the supercritical drying is CO2 supercritical drying, and the conditions for the CO2 supercritical drying are as follows: the temperature is 37 - 65°C, and the pressure is 7.3 - 15 Mpa.

[0084] As described above, the third aspect of the present invention provides the application of the polyimide aerogel film described in the first aspect in the fields of computers, communications, or consumer electronic products.

[0085] As described above, the fourth aspect of the present invention provides a polyimide aerogel film production system, which includes a batching unit, a defoaming unit, a coating and forming unit, an aging unit, a solvent replacement unit, and a supercritical drying unit;

[0086] Among them, the batching unit is used to sequentially introduce the raw materials for producing the polyimide aerogel film into the reaction kettle according to the reaction sequence for mixing reaction to obtain polyimide aerogel slurry I;

[0087] The defoaming unit is used to defoam the polyimide aerogel slurry I to obtain the polyimide aerogel slurry II;

[0088] The coating and forming unit includes a coating unit, a curing unit, and a winding unit; the coating unit is used to coat the polyimide aerogel slurry II between two layers of polymer auxiliary films to obtain a polyimide aerogel liquid film; the curing unit is used to cure the polyimide aerogel liquid film to obtain a polyimide aerogel solid film I; the winding unit is used to separate the polyimide aerogel solid film I and the two layers of polymer auxiliary films into three layers to obtain a polyimide aerogel solid film II;

[0089] The aging unit is kept airtight so that the unreacted monomers in the polyimide aerogel solid film II continue to react in the airtight environment to obtain a polyimide aerogel solid film III;

[0090] The solvent replacement unit is used to replace the solvent in the polyimide aerogel solid film III with a solvent that can be used for supercritical drying to obtain a polyimide aerogel solid film IV;

[0091] The supercritical drying unit is used to perform supercritical drying treatment on the polyimide aerogel solid film IV to obtain the polyimide aerogel film.

[0092] Preferably, the batching unit includes at least one raw material storage tank, at least one mixing tank, and at least one reaction kettle.

[0093] Preferably, the defoaming unit includes at least one centrifugal defoamer.

[0094] In the present invention, the centrifugal defoamer can rotate and revolve. The rotation provides a stirring function, and the revolution and vacuum provide a defoaming function. The front end of the equipment is connected to the batching tank, and the rear end is connected to the head of the coater, and it can automatically feed and discharge materials to ensure that the materials can be accurately transported and fed to the coater head.

[0095] Preferably, the coating unit includes at least one coater.

[0096] Preferably, the curing unit uses a seamless conveyor belt. To avoid damage to the material when it is conveyed on its surface.

[0097] Preferably, the winding unit includes at least one winder.

[0098] Preferably, the aging unit includes at least one aging kettle.

[0099] Preferably, the solvent replacement unit includes at least one replacement tank.

[0100] Preferably, the supercritical drying unit includes a CO2 supercritical drying device.

[0101] In the present invention, there is no particular requirement for the number of devices of each unit in the system, and those skilled in the art can adjust according to the actual production scale. An exemplary preferred combination mode is provided hereinafter in the present invention, and those skilled in the art should not understand it as a limitation to the present invention.

[0102] In some embodiments, the material after aging treatment in the aging kettle is introduced into the displacement tank for solvent displacement treatment. Preferably, the polyimide aerogel film production system of the present invention includes 3 - 6 aging kettles and 3 - 6 displacement tanks.

[0103] Figure 1 FIG. shows a schematic diagram of an optional polyimide aerogel film production system of the present invention. According to a particularly preferred specific embodiment of the present invention, the method for preparing a polyimide aerogel film of the present invention is carried out in the polyimide aerogel film production system, and the system includes a batching unit, a defoaming unit, a coating and forming unit, an aging unit, a solvent displacement unit, and a supercritical drying unit; the method includes:

[0104] 1) Performing a batching process in the batching unit,

[0105] Loading the organic solvent (referred to as liquid material A) into the liquid material tank A (V0101),

[0106] Loading the diamine I (referred to as powder material A) into the powder material tank A (V0102),

[0107] Loading the dianhydride monomer (referred to as powder material C) into the powder material tank C (V0103),

[0108] Loading the diamine II (referred to as powder material B) into the powder material tank B (V0104),

[0109] Loading the crosslinking agent (referred to as powder material D) into the powder material tank D (V0105),

[0110] Loading the dehydrating agent (referred to as liquid material B) into the liquid material tank B (V0106),

[0111] Loading the catalyst (referred to as liquid material C) into the liquid material tank C (V0107);

[0112] First, add a portion of liquid material A and powder material A to the reaction kettle R0101 according to a set ratio. After stirring and mixing evenly at 300 - 1200 rpm, add powder material B and powder material C to the reaction kettle R0101 in sequence for reaction. The reaction time is 30 - 120 min, and the reaction temperature is 18 - 25 °C; the portion of liquid material A accounts for 55 - 65% of the total mass of liquid material A.

[0113] Add the remaining portion of liquid material A and powder material D to the mixing tank 1 (V0108) according to a ratio, stir and mix evenly, and then the mixture in the mixing tank 1 (V0108) flows into the reaction kettle R0101 by gravity. React at 300 - 900 rpm and 18 - 25 °C for 4 - 10 min to obtain mixture I; liquid material A accounts for 75 - 95% of the total mass of mixture I.

[0114] Add liquid material B and liquid material C to the mixing tank 2 (V0109) in sequence according to a ratio, and then the mixture in the mixing tank 2 (V0109) flows into the reaction kettle R0101 by gravity. React at 300 - 2000 rpm and 18 - 25 °C for 1 - 10 min, and perform vacuum degassing treatment synchronously during the stirring reaction process; obtain polyimide aerogel slurry I.

[0115] Among them, the molar ratio of the amino groups provided by powder material A and powder material B to the anhydride groups provided by powder material C is n:(n + 1) or (n + 1):n, where n is an integer between 15 and 45.

[0116] Among them, powder material D is selected from at least one of 1,3,5 - tris(4 - aminophenoxy)benzene, 1,3,5 - benzenetricarbonyl trichloride, tris(2 - aminoethyl)amine, octa(aminophenyltrioxysilane), and tris(4 - aminophenyl)benzene.

[0117] Among them, the molar ratio of the dosage of liquid material B to powder material C is 6 - 8:1.

[0118] Among them, liquid material B is acetic anhydride, and liquid material C is pyridine and / or triethylamine; the molar ratio of the dosage of liquid material B to liquid material C is 1:1.

[0119] 2) Conduct a degassing process in the degassing unit.

[0120] Introduce polyimide aerogel slurry I into a centrifugal degassing machine and operate it at a set speed and time to obtain degassed polyimide aerogel slurry II.

[0121] 3) Conduct a coating and forming process in the coating and forming unit.

[0122] The polyimide aerogel slurry II is coated between polymer auxiliary films with a silicone oil coating on the surface to obtain a polyimide aerogel liquid film (PI aerogel film); the PI aerogel film is sandwiched between two layers of polymer auxiliary films and enters an oven for drying and curing treatment to obtain a polyimide aerogel solid film I; after the curing treatment is completed, the three-layer film is separately wound up to obtain a polyimide aerogel solid film II;

[0123] 4) Perform an aging process in the aging unit,

[0124] Add absolute ethanol to the aging kettle R0201, put the polyimide aerogel solid film II into the aging kettle R0201, keep it airtight, and let it stand at 18 - 45 °C for 5 - 24 h to obtain a polyimide aerogel solid film III;

[0125] 5) Perform a replacement process in the solvent replacement unit,

[0126] Add absolute ethanol to the replacement tank V0301, soak the polyimide aerogel solid film III in absolute ethanol for solvent replacement, and replace the absolute ethanol during the replacement process until the ethanol content in the replaced solvent is ≥ 99 vol% to obtain a polyimide aerogel solid film IV;

[0127] 6) Perform a drying process in the supercritical drying unit,

[0128] Put the polyimide aerogel solid film IV into a CO2 supercritical drying device for drying treatment to obtain a polyimide aerogel film.

[0129] The technical solution provided by the present invention preferably uses high-purity monomers, strictly controls the reaction time and the dosage ratio of reaction raw materials, enables the polymer to form a uniform molecular chain, is conducive to forming a stable gel structure. At the same time, the thickness of the film material prepared by this solution is small, and the solvent can enter the gel interior in a short time during replacement to complete the replacement.

[0130] The present invention has no special restrictions on the method of controlling the reaction time and the dosage of reaction raw materials. Those skilled in the art can select according to the known technical means in the art. Exemplarily, an automatic powder feeder with a precision of 0.001 g is used for feeding, and the feeding time and feeding amount are controlled by a program. The present invention will not elaborate here, and those skilled in the art should not understand it as a limitation to the present invention.

[0131] The present invention will be described in detail below through examples. In the following examples, unless otherwise specified, the raw materials used are commercially available products.

[0132] Polymer auxiliary film: Single-sided silicone oil is coated on a PET film, the release force is 15 g / cm, the light transmittance is 90%, the tensile strength is 100 MPa, and the thickness of the PET film is 70 μm. It is purchased from Dongguan Ruixin Plastics Industry Co., Ltd.

[0133] Example 1

[0134] Adopt Figure 1 The polyimide aerogel film production system shown is used to prepare the polyimide aerogel film.

[0135] 1) Perform the batching process in the batching unit.

[0136] Load an organic solvent (referred to as liquid material A) into the liquid material tank A (V0101).

[0137] Load diamine I (referred to as powder material A) into the powder material tank A (V0102).

[0138] Load the dianhydride monomer (referred to as powder material C) into the powder material tank C (V0103).

[0139] Load diamine II (referred to as powder material B) into the powder material tank B (V0104).

[0140] Load the crosslinking agent (referred to as powder material D) into the powder material tank D (V0105).

[0141] Load the dehydrating agent (referred to as liquid material B) into the liquid material tank B (V0106).

[0142] Load the catalyst (referred to as liquid material C) into the liquid material tank C (V0107).

[0143] First, add a part of liquid material A and powder material A to the reaction kettle R0101 according to a set ratio, stir and mix evenly, and then add powder material B and powder material C to the reaction kettle R0101 in sequence for the first reaction. A part of liquid material A accounts for 60% of the total mass of liquid material A.

[0144] Add the remaining part of liquid material A and powder material D to the mixing tank 1 (V0108) according to a ratio, stir and mix evenly, and then the mixture in the mixing tank 1 (V0108) flows into the reaction kettle R0101 by gravity for a contact reaction to obtain mixture I.

[0145] Add liquid material B and liquid material C to the mixing tank 2 (V0109) in sequence, and then the mixture in the mixing tank 2 (V0109) flows into the reaction kettle R0101 by gravity for the second reaction. During the stirring reaction process, vacuum degassing treatment is carried out synchronously to obtain the polyimide aerogel slurry I.

[0146] 2) Perform the degassing process in the degassing unit.

[0147] Introduce the polyimide aerogel slurry I into a centrifugal degassing machine and run it at a set speed and time to obtain the degassed polyimide aerogel slurry II.

[0148] 3) Perform the coating and forming process in the coating and forming unit.

[0149] Use a comma knife coater for coating. Before coating, clean the surfaces of the knife and the coating roller, adjust the gap between the comma knife and the coating roller, and then precisely calibrate it with a feeler gauge or a laser thickness gauge. Coat the polyimide aerogel slurry II between the polymer auxiliary films coated with silicone oil. The side coated with silicone oil is in direct contact with the defoamed material to obtain a polyimide aerogel liquid film. The PI aerogel film sandwiched between two layers of polymer auxiliary films enters the oven and is cured by a gradient heating method to obtain a polyimide aerogel solid film I. After the curing process is completed, the three-layer film is separately wound up to obtain a polyimide aerogel solid film II.

[0150] 4) Perform the aging process in the aging unit.

[0151] Put the polyimide aerogel solid film II into the aging kettle R0201, keep it airtight, and let it stand at 30°C for 12 hours to obtain a polyimide aerogel solid film III.

[0152] 5) Perform the replacement process in the solvent replacement unit.

[0153] Add anhydrous ethanol to the replacement tank V0301, soak the polyimide aerogel solid film III in anhydrous ethanol for solvent replacement, and replace the anhydrous ethanol during the replacement process until the ethanol content in the replaced solvent is ≥ 98 vol% to obtain a polyimide aerogel solid film IV.

[0154] 6) Perform the drying process in the supercritical drying unit.

[0155] Put the polyimide aerogel solid film IV into a CO2 supercritical drying equipment for drying treatment to obtain a polyimide aerogel film.

[0156] For the specific types of raw materials and process parameters, refer to those listed in Table 1 and Table  2.

[0157] Examples 2 - 3

[0158] The process similar to that of Example 1 is adopted, except that the types of raw materials and process parameters are different. For the specific details, refer to those listed in Table 1 and Table 2, and a polyimide aerogel film is prepared.

[0159] Example 4

[0160] The process is similar to that in Example 1, except that in the batching process, only diamine II containing a hydrophobic group is used as the diamine monomer to participate in the reaction. The type of diamine II is 4,4'-diamino-2,2'-dimethylbiphenyl, and the molar ratio of amino group to hydrophobic group is 1:1. The type and dosage of the dianhydride monomer are the same as those in Example 1, and the molar ratio of the amino group in the diamine monomer to the anhydride group in the dianhydride monomer is the same as that in Example 1. The rest remains unchanged, and a polyimide aerogel film is prepared.

[0161] Comparative Example 1

[0162] The process is similar to that in Example 1, except that in the batching process, the ratio of diamine I and diamine II is adjusted so that the molar ratio of amino group to hydrophobic group is 2:1. The type and dosage of the dianhydride monomer are the same as those in Example 1, and the molar ratio of the amino group in the diamine monomer to the anhydride group in the dianhydride monomer is the same as that in Example 1. The rest remains unchanged, and a polyimide aerogel film is prepared.

[0163] Comparative Example 2

[0164] The process is similar to that in Example 1, except that in the batching process, only diamine I without a hydrophobic group is used as the diamine monomer to participate in the reaction. The type of diamine I is the same as that in Example 1, the type and dosage of the dianhydride monomer are the same as those in Example 1, and the molar ratio of the amino group in the diamine monomer to the anhydride group in the dianhydride monomer is the same as that in Example 1. The rest remains unchanged, and a polyimide aerogel film is prepared.

[0165] Comparative Example 3

[0166] The process is similar to that in Example 1, except that in the batching process, the dosage of the diamine monomer is kept unchanged, and the dosage of the dianhydride monomer is adjusted so that the molar ratio of the amino group in the diamine monomer to the anhydride group in the dianhydride monomer is 1:1.2. The rest remains unchanged, and a polyimide aerogel film is prepared.

[0167] Table 1

[0168]

[0169]

[0170] Table 2

[0171]

[0172] Test Example

[0173] Test method for thickness standard deviation: The thickness of the target film is h0. Eight points of the thickness of the prepared film are selected, and the standard deviation is calculated according to the standard deviation formula, and the average value is recorded as h1.

[0174] Testing method for water absorption rate within 24 hours: Take a sample with a size of 3 cm × 3 cm, weigh its mass and record it as m0, immerse it in water for 24 hours, then take it out, wipe off the water on the surface, and weigh its mass and record it as m1; Water absorption rate (%) = (m1 - m0) / m0 × 100%.

[0175] The testing method for thermal conductivity is carried out with reference to GB / T 10295 - 2008.

[0176] The testing method for dielectric constant at 10 GHz is carried out with reference to GB / T 35679 - 2017.

[0177] The testing method for dielectric loss at 10 GHz is carried out with reference to GB / T 35679 - 2017.

[0178] Testing method for density: Carry out with reference to GB / T34336 - 2017.

[0179] Testing method for tensile strength: Refer to the standard of GB / T 17911 - 2006.

[0180] Testing method for light transmittance: Refer to the standard of ASTM D1003 - 21.

[0181] For the specific results, please refer to Table 3 and Table 4.

[0182] Table 3

[0183] Target thickness h0 / μm Average actual thickness h1 / μm Thickness standard deviation / % Example 1 100 100.6 4.84 Example 2 100 100.8 4.76 Example 3 100 101.2 2.82 Example 4 100 103.3 5.08 Comparative Example 1 100 102.2 2.82 Comparative Example 2 100 112.0 11.33 Comparative Example 3 100 98.9 18.03

[0184] Table 4

[0185]

[0186] It can be seen from the above results that by adopting the technical solution provided by the present invention, polyimide aerogel films with more uniform thickness and lower water absorption rate can be produced on a large scale. The present invention can achieve, under the condition of large - scale production, polyimide aerogel film products with stable quality, good hydrophobicity, good flexibility, low density, high tensile strength and good dielectric properties.

[0187] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, including any other suitable combination of each technical feature. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. A polyimide aerogel film, characterized in that, The standard deviation of the thickness of the polyimide aerogel film is ≤6%, and the water absorption rate in 24 hours is 2-10 wt%.

2. The polyimide aerogel film according to claim 1, wherein The thermal conductivity of the polyimide aerogel film is 0.015-0.025 W / (m·k); and / or, the dielectric constant of the polyimide aerogel film at 10 GHz is ≤1.5, and the dielectric loss at 10 GHz is ≤0.004; and / or, the density of the polyimide aerogel film is 0.06 - 0.15 g / cm 3 ; and / or, the tensile strength of the polyimide aerogel film is 1.5-5.0 MPa; and / or, the light transmittance of the polyimide aerogel film is ≥80%.

3. A method for preparing the polyimide aerogel film according to claim 1 or 2, characterized in that, This method includes: (1) In the presence of an organic solvent, a diamine monomer and a dianhydride monomer are subjected to a first reaction to obtain a mixture I; The diamine monomer contains an amino group and a hydrophobic group, and the molar ratio of the amino group to the hydrophobic group is 0.5-1.67:1; the molar ratio of the amino group in the diamine monomer to the anhydride group in the dianhydride monomer is 1:0.93-1.07; (2) The mixture I is subjected to a second reaction with a dehydrating agent and a catalyst to obtain a mixture II; (3) The mixture II is successively subjected to defoaming, coating and molding, aging, solvent replacement and supercritical drying to obtain the polyimide aerogel film.

4. The method according to claim 3, characterized in that, The method described in step (1) further includes: in the presence of an organic solvent, the intermediate product obtained by subjecting the diamine monomer and the dianhydride monomer to the first reaction is contacted with a crosslinking agent to obtain the mixture I; and / or, the crosslinking agent is selected from at least one of 1,3,5-tris(4-aminophenoxy)benzene, 1,3,5-benzenetricarbonyl trichloride, tris(2-aminoethyl)amine, octakis(aminophenyltrioxysilane), tris(4-aminophenyl)benzene.

5. The method according to claim 3 or 4, characterized in that In step (1), the diamine monomer is a combination of diamine I and diamine II, and the molar ratio of diamine I to diamine II is 0.1-2.5:1; diamine I is a diamine compound without a hydrophobic group, and diamine II is a diamine compound with a hydrophobic group; and / or, the diamine monomer is diamine II.

6. The method according to claim 5, characterized in that Diamine I is selected from at least one of 4,4-diaminodiphenyl ether, p-phenylenediamine, m-phenylenediamine, benzidine, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenyl sulfone, 1,5-naphthalenediamine, 3,3'-dimethoxybenzidine, 4,4'-diaminobenzyl, 1,3-cyclohexanediamine, 1,2-ethylenediamine, 1,12-diaminododecane, 4,4'-bis(4-aminophenoxy)biphenyl, 1,4-bis(4-aminophenoxy)benzene; And / or, the diamine II is selected from at least one of 3,3'-dimethyl-4,4'-diaminobiphenyl, 2,2-bis(3-amino-4-methylphenyl)hexafluoropropane, 3,3'-dimethyl-4,4'-diaminodiphenylmethane, 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl, 4,4'-(hexafluoroisopropylidene)dianiline, 4,4'-diaminooctafluorobiphenyl, 2,2'-bis(trifluoromethyl)-4,4'-diaminophenyl ether, 1,3-bis[2-(4-aminophenyl)-2-propyl]benzene, 4,4'-[1,4-phenylene-bis(1-methylethylene)]bis(N-phenyl)aniline, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, polyetheramine, 4,4'-diamino-2,2'-dimethylbiphenyl.

7. The method according to claim 3 or 4, characterized in that, In step (1), the organic solvent accounts for 75-95% of the total mass of the mixture I; And / or, in step (1), the dianhydride monomer is selected from at least one of 3,3',4,4'-biphenyltetracarboxylic dianhydride, hexafluorodiacid anhydride, pyromellitic dianhydride, diphenyl ether tetracarboxylic dianhydride, bisphenol A dianhydride, 3,3',4,4'-benzophenone tetracarboxylic dianhydride, 3,3,4,4-diphenylsulfone tetracarboxylic dianhydride, 9,9-bis(trifluoromethyl)xanthene tetracarboxylic dianhydride. And / or, in step (1), the organic solvent is selected from at least one of N-methylpyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide, dimethyl sulfoxide, diethyl sulfoxide, N-cyclohexyl-2-imidazolinone, diethylene glycol dimethyl ether, o-dichlorobenzene, acetonitrile, ethyl acetate, hexamethylphosphoramide, acetone.

8. The method according to claim 3 or 4, characterized in that In step (2), the dehydrating agent is selected from at least one of acetic anhydride, propionic anhydride, n-butyric anhydride, hexanoic anhydride, benzoic anhydride, heptanoic anhydride, trifluoroacetic anhydride; And / or, in step (2), the catalyst is pyridine and / or triethylamine; And / or, in step (2), the molar ratio of the amount of the dehydrating agent to the amount of the catalyst is 1:0.8-1.2; And / or, the molar ratio of the amount of the dehydrating agent to the amount of the dianhydride monomer is 6-~8:

1.

9. The method according to claim 4, wherein In step (1), the conditions of the first reaction include: the temperature is 18-25°C and the time is 30-120 min; And / or, in step (1), the conditions of the contact reaction include: the temperature is 18-25°C and the time is 4-10 min; And / or, in step (2), the conditions of the second reaction include: the temperature is 15-25°C and the time is 1-10 min.

10. The method according to claim 3 or 4, characterized in that In step (3), the operation of coating and forming includes: Introducing the defoamed material between two layers of polymer auxiliary films for coating and forming; the polymer auxiliary films are obtained by coating silicone oil on the surface of a polymer film, and the side coated with silicone oil is in direct contact with the defoamed material.

11. The method according to claim 10, wherein The conditions of the polymer film satisfy: the thickness is 50-150 μm; And / or, the polymer film is selected from at least one of PET film, PP film, PTFE film, PE film, PPS film, PI film; And / or, the release force of the polymer auxiliary film is 15 - 50 g / cm, the light transmittance is 75% - 95%, and the tensile strength is 50 - 150 MPa.

12. The application of the polyimide aerogel film according to claim 1 or 2 in the fields of computers, communications or consumer electronic products.

13. A production system for polyimide aerogel film, characterized in that, The system contains a batching unit, a defoaming unit, a coating and forming unit, an aging unit, a solvent replacement unit, and a supercritical drying unit; Among them, the batching unit is used to introduce the raw materials for producing the polyimide aerogel film into the reaction kettle in sequence according to the reaction sequence for mixing reaction to obtain polyimide aerogel slurry I; The defoaming unit is used to defoam the polyimide aerogel slurry I to obtain polyimide aerogel slurry II; The coating and forming unit includes a coating unit, a curing unit, and a winding unit; the coating unit is used to coat the polyimide aerogel slurry II between two layers of polymer auxiliary films to obtain a polyimide aerogel liquid film; the curing unit is used to cure the polyimide aerogel liquid film to obtain polyimide aerogel solid film I; the winding unit is used to separate the polyimide aerogel solid film I and the two layers of polymer auxiliary films into three layers to obtain polyimide aerogel solid film II; The aging unit is kept airtight so that the unreacted monomers in the polyimide aerogel solid film II continue to react in an airtight environment to obtain polyimide aerogel solid film III; The solvent replacement unit is used to replace the solvent in the polyimide aerogel solid film III with a solvent capable of supercritical drying to obtain polyimide aerogel solid film IV; The supercritical drying unit is used to perform supercritical drying treatment on the polyimide aerogel solid film IV to obtain the polyimide aerogel film.

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