Long-acting heat-insulating polyimide fiber and preparation method thereof

Abstract

The invention provides a long-acting heat-insulating polyimide fiber and a preparation method thereof, and belongs to the field of polyimide fibers.The long-acting heat-insulating polyimide fiber is prepared by adding pyromellitic dianhydride, 4, 4 '-diaminodiphenyl ether and triethylamine into an N, N-dimethylformamide solvent, conducting condensation polymerization at the preset temperature to obtain a polyamide acid solution, conducting spinning by adopting a centrifugal spinning technology, and obtaining the long-acting heat-insulating polyimide fiber. Auxiliary rods are arranged on the periphery of the centrifugal spinning cup, the polyamide acid fiber of a horizontal layered structure is formed, the fiber is subjected to cyclization reaction in an oxygen-containing environment, the curvature radius of the fiber is regulated and controlled through the oxygen concentration, and the long-acting heat-insulation polyimide fiber is obtained. A horizontal layered structure with a bent fiber form is formed by adopting a centrifugal spinning technology, the heat transfer efficiency is reduced by prolonging a heat conduction path, the bent structure not only enhances the heat insulation performance, but also can improve the mechanical stability through interlacing of fibers, the problem that traditional straight fibers are prone to brittle failure is solved, and the service life is prolonged. And through a bending structure and layered stacking, cooperative improvement of thermal resistance and mechanical properties is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of polyimide fibers, and in particular to a long-lasting heat-insulating polyimide fiber and a preparation method thereof. Background Art

[0002] Polyimide fibers, due to their high strength, high modulus, high-temperature resistance, flame retardancy, and chemical resistance, are widely used in aerospace, protective equipment, electronic devices, and other fields. In recent years, with the growing demand for high-efficiency thermal insulation materials, the application of polyimide fibers in thermal insulation has become a research hotspot. The thermal insulation performance of traditional polyimide fibers primarily relies on the material's inherent low thermal conductivity. However, under long-term high-temperature conditions, their thermal barrier properties gradually decline due to the short heat conduction path resulting from the simple fiber structure.

[0003] Existing polyimide fibers are typically produced using sol-gel spinning, dry-wet spinning, or electrospinning. These fibers often have straight fibers or simple layered structures, making it difficult to significantly extend the heat conduction path through structural design. Improving thermal insulation performance by adding phase change materials or compounding with other fibers presents challenges such as complex processing, increased costs, and poor stability.

[0004] In view of this, it is necessary to design a long-lasting thermal insulation polyimide fiber and a preparation method thereof to solve the above problems. Summary of the Invention

[0005] In view of the technical problems existing in the background technology, the present application provides a long-lasting thermal insulation polyimide fiber and a preparation method thereof, aiming to solve the technical problems that traditional polyimide fibers have a single structure, resulting in a short heat conduction path and thermal insulation performance that cannot meet long-term requirements.

[0006] In a first aspect, the present application provides a method for preparing a long-lasting thermal insulation polyimide fiber, comprising the following steps:

[0007] S1. Pyromellitic dianhydride, 4,4'-diaminodiphenyl ether and triethylamine are added to N,N-dimethylformamide solvent and subjected to polycondensation reaction at a predetermined temperature to obtain a polyamic acid solution;

[0008] S2 using centrifugal spinning technology to spin the polyamic acid solution, providing an auxiliary rod around the centrifugal spinning cup to form a horizontal layered structure of polyamic acid fibers;

[0009] S3. placing the horizontal layered polyamic acid fiber in an oxygen-containing environment for a cyclization reaction, and regulating the curvature radius of the fiber by adjusting the oxygen concentration to obtain a long-lasting thermal insulation polyimide fiber.

[0010] As a further improvement of the present application, in step S1, the mass fraction of the pyromellitic dianhydride is 5-10%, the mass fraction of the 4,4'-diaminodiphenyl ether is 5-10%, and the mass fraction of the triethylamine is 1-8%.

[0011] As a further improvement of the present application, the temperature of the polycondensation reaction is 0-10°C.

[0012] As a further improvement of the present application, the viscosity of the polyamic acid solution is 30 to 55 Pa·S.

[0013] As a further improvement of the present application, in step S2, the spinning speed of the centrifugal spinning technology is 3000-4000 rpm, the spinning temperature is 30-40°C, the spinning humidity is 30-40% RH; the spinneret diameter is 0.1-0.4 mm; and the distance between the centrifugal spinning cup and the collecting cloth is 5-15 cm.

[0014] As a further improvement of the present application, the auxiliary rods have a height of 5 to 15 cm, and are arranged with the centrifugal spinning cup as the center and 3 to 8 auxiliary rods placed at equal intervals with a radius of 5 to 25 cm.

[0015] As a further improvement of the present application, in step S3, the temperature of the cyclization reaction is 300-450° C., and the time is 1-3 hours.

[0016] As a further improvement of the present application, the oxygen concentration in the oxygen-containing environment is 5-50%, and the remaining component is nitrogen.

[0017] As a further improvement of the present application, the control range of the curvature radius is 10 to 300 μm.

[0018] In a second aspect, the present application provides a long-lasting thermal insulation polyimide fiber, which is prepared by the preparation method described in the first aspect. The long-lasting thermal insulation polyimide fiber has an apparent thermal conductivity of ≤0.04W / (m·K), a deformation recovery rate of >85%, and a compressive stress of ≥10MPa.

[0019] The beneficial effects of this application are:

[0020] The present application provides a heat-insulating polyimide fiber and a preparation method thereof, which comprises adding pyromellitic dianhydride, 4,4'-diaminodiphenyl ether and triethylamine to an N,N-dimethylformamide solvent, carrying out a polycondensation reaction at a predetermined temperature to obtain a polyamic acid solution, and spinning the fibers using centrifugal spinning technology. Auxiliary rods are arranged around the centrifugal spinning cup to form a horizontal layered structure polyamic acid fiber. The fibers are placed in an oxygen-containing environment for a cyclization reaction, and the curvature radius of the fibers is regulated by the oxygen concentration to obtain a long-lasting heat-insulating polyimide fiber. The present application adopts centrifugal spinning technology to form a horizontal layered structure with a curved fiber morphology, and reduces the heat transfer efficiency by extending the heat conduction path. Through centrifugal spinning and imidization treatment of PAA (polyamic acid) solution, a curved fiber network is formed in one step, avoiding additional compounding steps and reducing costs. The curved structure not only enhances the thermal insulation performance, but also improves the mechanical stability by interlacing between fibers, thereby solving the problem of brittle fracture of traditional straight fibers.

[0021] This application uses centrifugal spinning technology to form PAA fiber textiles in a single step. Compared to traditional electrospinning or sol-gel spinning processes (which require multiple steps to adjust the electric field or solvent volatilization), the spinning speed is increased by 3 to 5 times, and complex parameter control (such as voltage regulation) is not required, significantly shortening the production cycle. The centrifugal spinning process is more adaptable to solution concentration and viscosity, does not require high-energy solvent recovery equipment (such as wet spinning, which requires large amounts of solvent removal), and improves raw material utilization by 20 to 30%.

[0022] The long-lasting thermal insulation polyimide fiber obtained in this application is a horizontal layered structure in a curved form, which extends the heat conduction path by 30 to 50%. The apparent thermal conductivity of the horizontal layered polyimide fiber is ≤0.04W / (m·K). After continuous use at 300°C for 1000 hours, the thermal barrier efficiency still maintains more than 90% of the initial value. The horizontal layered structure formed by the interlacing of fibers gives the material higher compressive stress (≥10MPa) and anti-compression resilience (deformation recovery rate>85%), which is suitable for dynamic stress environments (such as aircraft thermal insulation pads). The synergistic improvement of thermal resistance and mechanical properties is achieved through curved structure and layered stacking, without relying on added materials (such as phase change agents or reinforcing fibers), and has intrinsic performance advantages.

[0023] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] To more clearly illustrate the technical solution of this application, the following is a brief introduction to the drawings used in this application. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be derived from these drawings without inventive effort.

[0025] Figure 1 A schematic diagram of the auxiliary rod arrangement for the method for preparing the long-lasting heat-insulating polyimide fiber provided in this application;

[0026] Figure 2 Schematic diagram of the horizontal layered structure of the long-lasting thermal insulation polyimide fiber provided in this application;

[0027] Figure 3 A physical picture of the long-lasting thermal insulation polyimide fiber provided in Example 1 of the present application;

[0028] Figure 4 This is an SEM image of the long-lasting thermal insulation polyimide fiber provided in Example 1 of the present application. DETAILED DESCRIPTION

[0029] The following embodiments of the technical solution of the present application will be described in detail with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present application and are therefore only examples and are not intended to limit the scope of protection of the present application.

[0030] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the specification and claims of this application and the above-mentioned figure descriptions are intended to cover non-exclusive inclusions.

[0031] In the description of the embodiments of this application, the technical terms "first" and "second" are used only to distinguish different objects and should not be understood to indicate or imply relative importance or implicitly specify the quantity, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, the meaning of "plurality" is more than two, unless otherwise clearly and specifically defined.

[0032] References herein to "embodiments" mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0033] The fibers formed by traditional spinning technology are mostly straight fibers or simply layered arrangements. The heat conduction path is direct, heat is easily and quickly transferred, and performance improvement depends on added materials (such as phase change agents). There are problems such as complex process and poor stability.

[0034] In order to solve the technical problems that traditional polyimide fibers have a single structure, resulting in a short heat conduction path and difficulty in synergistic optimization of mechanical stability and thermal insulation performance, the present application provides a long-lasting thermal insulation polyimide fiber and a preparation method thereof, wherein, by preparing horizontal layered polyamic acid fibers and regulating the curvature radius of the fibers, the heat conduction path is extended, the heat transfer efficiency is reduced, the thermal insulation performance is enhanced, and the mechanical stability is improved.

[0035] In a first aspect, an embodiment of the present application provides a method for preparing a thermal insulating polyimide fiber, comprising the following steps:

[0036] S1. Pyromellitic dianhydride, 4,4'-diaminodiphenyl ether and triethylamine are added to N,N-dimethylformamide solvent and subjected to polycondensation reaction at a predetermined temperature to obtain a polyamic acid solution;

[0037] S2 using centrifugal spinning technology to spin the polyamic acid solution, providing an auxiliary rod around the centrifugal spinning cup to form a horizontal layered structure of polyamic acid fibers;

[0038] S3. The horizontal layered polyamic acid fiber is placed in an oxygen-containing environment for a cyclization reaction, and the curvature radius of the fiber is regulated by the oxygen concentration to obtain a long-lasting thermal insulation polyimide fiber.

[0039] In the technical scheme of the embodiment of the present application, a polyamic acid solution is prepared by a polycondensation reaction, and the contents of pyromellitic dianhydride (PMDA), 4,4'-diaminodiphenyl ether (ODA) and triethylamine (TEA) are controlled to adjust the viscosity of the polyamic acid solution, thereby affecting the performance of the final fiber. The polyamic acid solution is made into fibers by centrifugal spinning technology. Auxiliary rods are arranged around the centrifugal spinning cup. The function of these auxiliary rods is to guide and interfere with the deposition path of the fiber, thereby forming a fiber with a horizontal layered structure. The formed horizontal layered structure polyamic acid fiber is subjected to a next step of cyclization reaction (i.e., imidization reaction) to form a horizontal layered structure polyimide fiber. The reaction needs to be carried out under high temperature oxygen-containing conditions. High temperature oxygen-containing conditions cause the chain structure of the polyimide macromolecule to change, resulting in changes in the aggregated structure, causing stress differences in the fiber, causing the fiber to bend. After imidization, a horizontal layered structure polyimide fiber textile with a curved fiber morphology is formed. The layered structure can hinder the transfer of heat, optimize the thermal insulation properties of the fiber, and extend the service life.

[0040] Furthermore, in some embodiments, in step S1, the mass fraction of pyromellitic dianhydride is 5-10%, the mass fraction of 4,4'-diaminodiphenyl ether is 5-10%, and the mass fraction of triethylamine is 1-8%. The viscosity of the polyamic acid solution is 30-55 Pa·s.

[0041] In the technical solution of the embodiment of the present application, by adjusting the content of pyromellitic dianhydride, 4,4'-diaminodiphenyl ether and triethylamine, the viscosity of the polyamic acid solution can be effectively controlled, the stability and controllability of the spinning process can be improved, and the thermal insulation properties of the final polyimide fiber can be enhanced.

[0042] Furthermore, in some embodiments, the temperature of the polycondensation reaction is 0-10°C.

[0043] In the technical solution of the embodiment of the present application, the condensation reaction is carried out at a low temperature, which can avoid the generation of by-products or uneven molecular weight distribution due to too rapid reaction, improve the stability of the solution, and by controlling the temperature of the condensation reaction, the structure and properties of the polyamic acid can be better regulated, thereby improving the performance of the polyimide fiber finally spun.

[0044] Furthermore, in some embodiments, in step S2, the spinning speed of the centrifugal spinning technology is 3000-4000 rpm, the spinning temperature is 30-40°C, the spinning humidity is 30-40% RH; the spinneret diameter is 0.1-0.4 mm; and the distance between the centrifugal spinning cup and the collecting cloth is 5-15 cm.

[0045] In the technical solutions of the embodiments of this application, high rotation speeds help evenly stretch the solution, forming fibers with consistent diameters. The spinning temperature and humidity maintain the fluidity and stability of the polymer solution, preventing changes in solution viscosity caused by excessively high or low temperatures. The spinneret diameter determines the initial diameter of the filaments, which in turn influences the diameter and properties of the final fibers. An appropriate distance between the centrifugal spinning cup and the collecting cloth reduces the risk of filament breakage during flight, improving fiber integrity and continuity.

[0046] Furthermore, in some embodiments, the auxiliary rods have a height of 5 to 15 cm, and are arranged such that 3 to 8 auxiliary rods are placed at equal intervals with a radius of 5 to 25 cm, centered on the centrifugal spinning cup.

[0047] In the technical solution of the embodiment of the present application, auxiliary rods are provided to assist in forming a horizontal layered structure. Figure 1As shown, auxiliary rods are arranged at equal intervals around the centrifugal spinning cup. By adjusting the height of the auxiliary rods, the thickness of the fiber deposition on the collecting cloth can be controlled, thereby affecting the thickness and density of the final fiber layer. Within the same spinning time, different rod heights and setting radii affect the height and porosity of the layered aggregate. The auxiliary rods are arranged at equal intervals within a certain radius around the centrifugal spinning cup, guiding the fibers to be evenly distributed under the action of centrifugal force, forming a regular layered structure. By properly setting the rod height and arrangement of the auxiliary rods, the fiber deposition and molding process can be effectively controlled, forming a uniform and regular horizontal layered structure of polyamic acid fibers. This structure helps improve the mechanical properties, thermal insulation properties, and structural stability of the fiber.

[0048] Furthermore, in some embodiments, in step S3, the cyclization reaction temperature is 300-450° C., the reaction time is 1-3 hours, the oxygen concentration is 5-50%, and the remaining component is nitrogen.

[0049] In the technical solution of the embodiments of this application, the cyclization reaction process of polyamic acid fibers can be effectively controlled by properly setting the temperature, time, oxygen concentration, and nitrogen ratio of the cyclization reaction. The high temperature and oxygen-containing conditions promote changes in the chain structure of the polyimide macromolecules, leading to changes in the aggregate structure, causing stress differences within the fibers and causing fiber bending. By optimizing the crystallinity and orientation of the fibers, the mechanical properties and thermal stability of the fibers are improved.

[0050] Furthermore, in some embodiments, the curvature radius of the fiber is controlled in the range of 10 to 300 μm.

[0051] In the technical solution of the embodiments of this application, the fibers are adjusted to achieve different curved shapes by adjusting the radius of curvature. Adjusting the height and radius of the long rods optimizes the height and porosity of the layered aggregate to achieve optimal thermal insulation. The curved structure and layered stacking achieve a synergistic improvement in thermal resistance and mechanical properties.

[0052] In a second aspect, an embodiment of the present application provides a long-lasting thermal insulation polyimide fiber, which is prepared by the preparation method described in the first aspect. The apparent thermal conductivity of the fiber is ≤0.04W / (m·K), the deformation recovery rate is >85%, and the compressive stress is ≥10MPa.

[0053] In the technical solution of the embodiment of the present application, the structural diagram of the obtained long-lasting heat-insulating polyimide fiber is as follows: Figure 2 As shown in the figure, by precisely controlling the preparation process, the prepared fibers show significant advantages in thermal insulation, mechanical properties and structural stability, and can meet the needs of a variety of harsh application scenarios, especially in high temperature, high pressure and dynamic load environments, and have broad application prospects.

[0054] Some specific examples are listed below. It should be noted that the examples described below are exemplary and are only used to explain the present application, and should not be construed as limiting the present application. Where specific techniques or conditions are not specified in the examples, the techniques or conditions described in the literature in this area or the product specifications are used. Reagents or instruments used without manufacturer's indication are all commercially available conventional products.

[0055] Example 1

[0056] This embodiment provides a method for preparing a thermal insulation polyimide fiber, comprising the following steps:

[0057] S1. PMDA, ODA, and TEA were added to N,N-dimethylformamide solvent and subjected to polycondensation reaction at 3°C to obtain a polyamic acid solution; wherein the mass fraction of PMDA was 8%, the mass fraction of ODA was 8%, and the mass fraction of TEA was 2%;

[0058] S2. A polyamic acid solution was spun using centrifugal spinning technology. Auxiliary rods were placed around the centrifugal spinning cup. Six auxiliary rods, each 9 cm high, were placed evenly spaced at a radius of 10 cm around the centrifugal spinning cup to form a horizontal layered structure of polyamic acid fibers. The spinning speed was 3500 rpm, the spinning temperature was 35°C, the spinning humidity was 35% RH, and the spinneret diameter was 0.2 mm. The distance between the centrifugal spinning cup and the collecting cloth was 10 cm.

[0059] S3. The horizontal layered polyamic acid fiber is placed in an oxygen-containing environment for cyclization reaction. The cyclization reaction temperature is 380 ° C, the time is 2 hours, the oxygen concentration is 20%, and the remaining components are nitrogen, to obtain a long-lasting thermal insulation polyimide fiber, such as Figures 3 and 4 As shown, it can be seen that the fiber has a multi-layer curved fiber structure and is lightweight.

[0060] Examples 2-3 and Comparative Examples 1-2

[0061] Examples 2-3 and Comparative Examples 1-2 respectively provide a method for preparing a thermal insulating polyimide fiber. Compared with Example 1, the only difference is that the oxygen concentration is different, as shown in Table 1. Other experimental parameters and conditions are basically the same as those in Example 1 and will not be repeated here.

[0062] Comparative Example 3

[0063] Comparative Example 3 provides a method for preparing thermal insulating polyimide fiber. Compared with Example 1, the only difference is that no auxiliary rod is provided. Other experimental parameters and conditions are basically the same as those in Example 1 and will not be repeated here.

[0064] Examples 4-5

[0065] Examples 4-5 respectively provide a method for preparing thermal insulating polyimide fibers. Compared with Example 1, the only difference is that the height of the auxiliary rod is different, as shown in Table 1. Other experimental parameters and conditions are basically the same as those in Example 1 and will not be repeated here.

[0066] Comparative Examples 4-5

[0067] Comparative Examples 4-5 respectively provide a method for preparing an insulating polyimide fiber. Compared with Example 1, the only difference is that the mass fractions of PMDA, ODA and TEA are different. In Comparative Example 4, the mass fraction of PMDA is 15%, the mass fraction of ODA is 5%, and the mass fraction of TEA is 2%. In Comparative Example 5, the mass fraction of PMDA is 5%, the mass fraction of ODA is 15%, and the mass fraction of TEA is 2%. The other experimental parameters and conditions are basically the same as those in Example 1 and will not be repeated here.

[0068] Test method:

[0069] Apparent thermal conductivity: tested according to GB / T 10294-2008 Insulation materials - Determination of steady-state thermal resistance and related properties - Guarded hot plate method standard and method;

[0070] Deformation recovery rate: calculated based on the height difference of the horizontal layered polyimide fiber before and after compression.

[0071] Compression stress: Tested according to GB / T 18942.1-2003 Determination of compressive stress-strain characteristics of polymer porous elastic materials Part 1: Low density materials

[0072] Thermal insulation efficiency: Calculated based on the ratio of the temperature difference between the near high-temperature surface and the back high-temperature surface to the temperature of the high-temperature object when the horizontal layered polyimide fiber is used to insulate the high-temperature object.

[0073] The test results are shown in Table 1.

[0074] Table 1 Performance test results

[0075]

[0076]

[0077] As can be seen from Table 1, the long-lasting thermal insulation polyimide fiber prepared in this application is a horizontal layered structure fiber with a curved shape. The apparent thermal conductivity of the fiber is ≤0.04W / (m·K). After continuous use for 1000 hours at 300°C, the thermal barrier efficiency still maintains more than 90% of the initial value. The horizontal layered structure formed by the interlacing of the fibers gives the material a higher compressive stress (≥10MPa) and anti-compression resilience (deformation recovery rate>85%). In Comparative Example 1, due to the cyclization reaction in an oxygen-free environment, the average curvature radius of the fiber is large, indicating that the degree of bending is small. In Comparative Example 2, the O2 concentration is excessive, and the aromatic rings in the polyimide react with excess oxygen to cause the polyimide molecular chain to break, causing the polyimide fiber to undergo oxidative degradation. In Comparative Example 3, no auxiliary rod is provided, which results in the fiber being unable to form a horizontal layered structure. In Comparative Examples 4-5, due to changes in the mass ratio of the raw materials PMDA and ODA, the reaction is unbalanced during the synthesis of polyamic acid, and the fibers finally obtained are straight fibers.

[0078] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and any embodiments having substantially the same structure and effect as the technical concept within the scope of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the present application, any other embodiments that can be conceived by those skilled in the art and that combine some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A method for preparing long-lasting thermal insulation polyimide fiber, characterized in that: The following steps are involved: S1. Pyromellitic dianhydride, 4,4'-diaminodiphenyl ether and triethylamine are added to N,N-dimethylformamide solvent and subjected to polycondensation reaction at a predetermined temperature to obtain a polyamic acid solution; S2 using centrifugal spinning technology to spin the polyamic acid solution, providing an auxiliary rod around the centrifugal spinning cup to form a horizontal layered structure of polyamic acid fibers; S3. placing the horizontal layered polyamic acid fiber in an oxygen-containing environment for a cyclization reaction, and regulating the curvature radius of the fiber by adjusting the oxygen concentration to obtain a long-lasting thermal insulation polyimide fiber.

2. The method for preparing the long-lasting thermal insulation polyimide fiber according to claim 1, wherein: In step S1 , the mass fraction of the pyromellitic dianhydride is 5-10%, the mass fraction of the 4,4'-diaminodiphenyl ether is 5-10%, and the mass fraction of the triethylamine is 1-8%.

3. The method for preparing the long-lasting thermal insulation polyimide fiber according to claim 2, wherein: The temperature of the polycondensation reaction is 0-10°C.

4. The method for preparing the long-lasting thermal insulation polyimide fiber according to claim 3, characterized in that: The viscosity of the polyamic acid solution is 30-55 Pa·S.

5. The method for preparing the long-lasting thermal insulation polyimide fiber according to claim 1, wherein: In step S2, the spinning speed of the centrifugal spinning technology is 3000-4000 rpm, the spinning temperature is 30-40°C, the spinning humidity is 30-40% RH; the spinneret diameter is 0.1-0.4 mm; and the distance between the centrifugal spinning cup and the collecting cloth is 5-15 cm.

6. The method for preparing the long-lasting thermal insulation polyimide fiber according to claim 5, characterized in that: The auxiliary rods have a height of 5 to 15 cm, and are arranged in such a manner that 3 to 8 auxiliary rods are placed at equal intervals with a radius of 5 to 25 cm, with the centrifugal spinning cup as the center.

7. The method for preparing the long-lasting thermal insulation polyimide fiber according to claim 1, characterized in that: In step S3, the cyclization reaction temperature is 300-450° C., and the time is 1-3 hours.

8. The method for preparing the long-lasting thermal insulation polyimide fiber according to claim 7, characterized in that: The oxygen concentration in the oxygen-containing environment is 5-50%, and the remaining component is nitrogen.

9. The method for preparing the long-lasting thermal insulation polyimide fiber according to claim 8, characterized in that: The control range of the curvature radius is 10 to 300 μm.

10. A long-lasting thermal insulation polyimide fiber, characterized in that: The long-lasting thermal insulation polyimide fiber is prepared by the preparation method according to any one of claims 1 to 9, wherein the apparent thermal conductivity of the long-lasting thermal insulation polyimide fiber is ≤0.04W / (m·K), the deformation recovery rate is >85%, and the compressive stress is ≥10MPa.

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