A porous polyimide-solid oil oil storage material and a method for preparing the same

Abstract

This invention belongs to the field of lubrication, specifically relating to a porous polyimide-solid oil storage material and its preparation method. The preparation method includes the following steps: (1) pressing polyimide powder and then sintering it to obtain porous polyimide; (2) mixing solid oil powder with lubricating oil to obtain a liquid mixture; (3) immersing the porous polyimide into the liquid mixture and applying a vacuum to allow the liquid mixture to enter the pores of the porous polyimide, thereby obtaining a pre-made oil storage material; (4) curing the pre-made oil storage material to obtain the porous polyimide-solid oil storage material. This invention utilizes the high porosity and excellent mechanical properties provided by porous polyimide, and the high oil content and excellent oil retention rate provided by solid oil embedded in the pores, thus solving the technical problem of the mutual constraint between porosity and oil retention rate in traditional porous polyimide oil-containing materials.

Description

Technical Field

[0001] This invention belongs to the field of lubrication, specifically relating to a porous polyimide-solid oil storage material and its preparation method. Background Technology

[0002] Porous polyimide materials are a class of functional polymer materials with a continuous microporous structure. Their internal pores form a series interconnected structure, exhibiting excellent oil retention and good mechanical properties. Bearing retainers or oil reservoirs made from porous polyimide materials are widely used in high-speed, high-precision bearings and key components in aerospace satellite gyroscopes, high-end machine tool spindles, and precision instruments, serving as one of the core functional components of high-end equipment lubrication systems.

[0003] Ideally, when a bearing operates at high speed, the lubricating oil stored in the micropores of the porous polyimide oil-impregnated material gradually seeps out to the surface of the friction pair under the action of centrifugal force and frictional temperature rise, forming a continuous lubricating film to reduce friction and wear. When the bearing stops operating, the lubricating oil is reabsorbed back into the micropores for storage under the action of capillary force. This "seepage-adsorption" cycle mechanism allows the porous polyimide oil-impregnated material to be repeatedly recycled, maximizing the utilization rate of lubricating oil and ensuring that mechanical parts achieve pollution-free, long-life, and maintenance-free operation.

[0004] However, with the rapid development of modern industrial technology, high-end equipment places increasingly higher demands on the limiting speed, service life, and reliability of high-speed bearings and key components. This also places higher requirements on the oil content and oil-locking performance of porous polyimide oil retainers or oil reservoirs. Currently, porous polyimide oil-impregnated materials typically employ a one-time "thin oil" lubrication method, where liquid lubricating oil is directly immersed in the pores of the porous material. Under high-speed operating conditions, the centrifugal force increases dramatically, and the liquid lubricating oil is easily thrown out of the pores, leading to lubrication failure. This, in turn, causes a series of problems such as accelerated bearing wear, shortened service life, and lubricant splashing that pollutes the environment.

[0005] More importantly, there is an inherent mutually restrictive relationship between the porosity and oil retention rate of porous polyimide materials: when the material porosity is large, its oil content is high, but the corresponding pore size is also large, resulting in poor oil retention and easy lubrication loss during high-speed operation; conversely, when the material porosity is small, the pore size is small, resulting in better oil retention, but the oil content is low, which cannot meet the requirements for long-life lubrication. Current technologies struggle to simultaneously achieve a balance between high oil content and high oil retention rate, which has become a key technological bottleneck restricting the development of the high-speed bearing and precision machinery industries.

[0006] To address the aforementioned problems, those skilled in the art have made various attempts. For example, modifying the surface of porous polyimide materials aims to improve their oleophilicity or oil-locking properties without altering the pore structure. However, the modified surface layer is prone to detachment and failure under long-term friction and wear, resulting in limited effectiveness and poor durability. Another approach involves using composite lubrication technology, adding thickeners or nanoparticles to lubricating oil to enhance oil film strength. However, thickeners are prone to degradation at high temperatures and speeds, while nanoparticles pose a risk of agglomeration and accelerated wear. Yet another approach involves developing solid lubricating coating technology to prepare a solid lubricating film on the friction surface to reduce dependence on liquid lubricating oil. However, the bonding strength between the solid coating and the substrate is insufficient, and self-replenishing lubrication cannot be achieved, thus limiting its service life.

[0007] Therefore, based on this, the technical solution of the present invention is proposed. Summary of the Invention

[0008] To address the technical problem of the mutual constraint between porosity and oil retention rate in existing technologies, this invention provides a porous polyimide-solid oil storage material and its preparation method. This invention employs a structure where solid oil is "embedded" in a microporous polyimide material, ensuring both good mechanical properties and a high lubricant retention rate in the retainer or oil reservoir ring, thus guaranteeing a longer service life for bearings and other high-speed applications.

[0009] The present invention provides a method for preparing a porous polyimide-solid oil storage material, the preparation method comprising the following steps:

[0010] (1) The polyimide powder is first pressed and then sintered to obtain porous polyimide; (2) The solid oil powder and lubricating oil are stirred and mixed to obtain a liquid mixture; (3) The porous polyimide is immersed in the liquid phase mixture and a vacuum is applied to allow the liquid phase mixture to enter the pores of the porous polyimide, thereby obtaining a prefabricated oil storage material. (4) The prefabricated oil storage material is cured to obtain the porous polyimide-solid oil storage material.

[0011] Preferably, in step (1), polyimide powder and lubricant are loaded into a mold and pressed to form a blank; then the blank is taken out and placed in a PTFE sintering furnace and sintered at 365-380℃ for 15-35 minutes to form a porous polyimide. The lubricant is polytetrafluoroethylene powder, and the weight ratio of the polyimide powder to the polytetrafluoroethylene powder is 90-95:10-5.

[0012] Preferably, in step (2), the solid oil powder and lubricating oil are stirred and mixed in a weight ratio of 10-30:90-70 to obtain a liquid mixture; The solid oil powder is polyethylene solid oil powder, and the particle size of the polyethylene solid oil powder is 500-1500 nm; the polyethylene can be one or a combination of two or more of low-density polyethylene, medium-density polyethylene, high-density polyethylene or ultra-high molecular weight polyethylene.

[0013] The lubricating oil is one or a combination of two or more of mineral oil, semi-synthetic oil, and fully synthetic oil.

[0014] Preferably, in step (3), the porous polyimide is immersed in the liquid phase mixture, and a vacuum is drawn to a pressure of 1-10 kPa and maintained for 4-8 hours, so that the liquid phase mixture enters the pores of the porous polyimide to obtain a pre-made oil storage material.

[0015] Preferably, in step (4), the pre-made oil storage material is cured at 150-180°C to obtain the porous polyimide-solid oil storage material.

[0016] Based on the same technical concept, the present invention further provides an oil storage material of porous polyimide-solid oil obtained by the above preparation method.

[0017] Preferably, the porous polyimide-solid oil storage material comprises a porous polyimide material and a solid oil material; wherein: The solid oil material is embedded inside the pores of the porous polyimide material.

[0018] Preferably, the porous polyimide material has a porosity of 25-50% and a pore diameter of 2.5-3.5 μm; The solid oil material has an oil content of 70-90% and a pore diameter of 0.5-1.5 μm.

[0019] The beneficial effects of this invention are as follows: (1) The present invention adopts a composite structure of porous polyimide "embedded" solid oil. The porous polyimide provides a high porosity of 25-50% and a pore size of 2.5-3.5μm, ensuring a high oil storage space for the material. The polyethylene solid oil embedded in the pores has an oil content of up to 70-90%, and the internal pore size of the solid oil is only 0.5-1.5μm. It can effectively lock in the lubricating oil by means of capillary effect, thereby achieving both high oil content and high oil retention rate in the whole, solving the technical problem of mutual restriction between porosity and oil retention rate in traditional porous materials.

[0020] (2) The present invention uses porous polyimide as the skeleton material. Polyimide itself has excellent mechanical properties such as high strength, high modulus, wear resistance and high temperature resistance. Furthermore, the pore structure can be precisely controlled through powder pressing and sintering process, so that the material can maintain high porosity while still having sufficient mechanical strength, which can meet the load-bearing and wear-resistant requirements of structural components such as high-speed bearing retainers and oil reservoir rings.

[0021] (3) In the oil storage material of the present invention, solid oil is uniformly distributed in the polyimide pores in the form of micro oil storage units. During the friction process, lubricating oil can be slowly released to achieve a continuous and stable self-lubricating effect. At the same time, the solid state of solid oil effectively inhibits the loss of lubricating oil under the action of high-speed centrifugal force, significantly prolongs the lubrication life, and enables long-term maintenance-free operation of mechanical parts.

[0022] (4) Under high-speed rotation conditions of 6000-12000r / min, the oil retention rate of the oil storage material of the present invention can still reach more than 99% after 120 minutes in a room temperature environment. Even in a higher temperature environment of 60℃, the oil retention rate is still maintained at more than 97%, which is far superior to the porous polyimide material of traditional thin oil lubrication. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a scanning electron microscope image of the porous polyimide obtained in Example 1.

[0025] Figure 2 This is a physical image of the porous polyimide-solid oil storage material obtained in Example 1.

[0026] Figure 3 This is a picture of the actual device used for the centrifugal oil-spraying test. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be described in detail below. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other implementation methods obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0028] This invention provides a method for preparing a porous polyimide-solid oil storage material, the method comprising the following steps: (1) The polyimide powder and lubricant are loaded into a mold and pressed to form a blank; then the blank is taken out and placed in a PTFE sintering furnace and sintered at 365-380℃ for 15-35 minutes to form a porous polyimide; the lubricant is PTFE powder, and the weight ratio of the polyimide powder to the PTFE powder is 90-95:10-5.

[0029] (2) The solid oil powder and the lubricating oil are stirred and mixed in a weight ratio of 10-30:90-70 to obtain a liquid phase mixture; the solid oil powder is polyethylene solid oil powder with a particle size of 500-1500nm; the lubricating oil is one or a combination of two or more of mineral oil, semi-synthetic oil and fully synthetic oil.

[0030] (3) Immerse the porous polyimide into the liquid phase mixture, and evacuate to a pressure of 1-10 kPa and maintain for 4-8 hours to allow the liquid phase mixture to enter the pores of the porous polyimide to obtain a pre-made oil storage material.

[0031] (4) The pre-made oil storage material is cured at 150-180°C to obtain the porous polyimide-solid oil storage material.

[0032] Example 1 This embodiment provides a method for preparing a porous polyimide-solid oil storage material, the preparation method comprising the following steps: (1) Polyimide powder and lubricant polytetrafluoroethylene powder are mixed evenly in a high-speed mixer at a weight ratio of 95:5. The mixture is then placed into a custom mold and cold-pressed under a pressure of 20 MPa to obtain a blank with a certain shape and size. After demolding, the blank is removed and placed in a PTFE sintering furnace. It is then sintered at 365°C for 35 min to form a high-temperature sintering structure, which causes the polyimide particles to melt and bond together, forming a porous polyimide matrix with a continuous interconnected microporous structure (scanning electron microscope image as shown). Figure 1 As shown, the pore size distribution is uniform. In this step, polytetrafluoroethylene powder acts as a lubricant, which can improve the powder flowability and pressing uniformity. At the same time, some of it volatilizes or migrates during sintering, which helps to control the porosity and pore size distribution.

[0033] (2) Medium-density polyethylene solid oil powder with a particle size of 500-1000nm and mineral lubricating oil are added to a stirring vessel at a weight ratio of 20:80. The mixture is stirred and mixed at a speed of 500r / min for 2h under a heating condition of 60℃, so that the polyethylene solid oil powder is fully swollen and uniformly dispersed in the lubricating oil to form a uniform and stable liquid phase mixture.

[0034] (3) The porous polyimide matrix obtained in step (1) is completely immersed in the liquid phase mixture prepared in step (2), placed in a vacuum impregnation tank, and evacuated to a pressure of 5 kPa, and maintained for 6 hours. Under vacuum, the air in the pores of the porous polyimide is extracted, and the liquid phase mixture fully penetrates into the pores under the combined action of pressure difference and capillary force. After impregnation, it is taken out and excess liquid on the surface is drained to obtain the pre-made oil storage material. In this step, the selection of vacuum degree needs to take into account both impregnation efficiency and process feasibility: if the vacuum degree is too low, the air in the pores will not be completely removed, and the impregnation will be insufficient; if the vacuum degree is too high, it will cause the light components of the lubricating oil to volatilize, affecting the performance of the oil. Maintaining for 6 hours is to ensure that the liquid phase mixture can completely fill all the interconnected pores.

[0035] (4) Place the pre-made oil storage material obtained in step (3) in a forced-air drying oven and heat it at 150°C for 2 hours to allow the polyethylene solid oil powder in the pores to fully melt and recrystallize and solidify, forming a solid oil microstructure with polyethylene as the carrier and encapsulating lubricating oil. After cooling to room temperature, the porous polyimide-solid oil storage material is obtained (see actual picture). Figure 2 (As shown).

[0036] Example 2 This embodiment provides a method for preparing a porous polyimide-solid oil storage material, which is basically the same as that in Example 1. The preparation method includes the following steps: (1) Polyimide powder and polytetrafluoroethylene powder are mixed evenly in a high-speed mixer at a weight ratio of 92:8, and then placed into a custom mold. The mixture is cold-pressed under a pressure of 25 MPa to obtain a blank. After demolding, the blank is removed and placed in a PTFE sintering furnace. It is then sintered at 372°C for 25 min to obtain a porous polyimide matrix. In this embodiment, the amount of polytetrafluoroethylene powder added is slightly higher than that in Example 1, which helps to further improve the powder pressing performance and fine-tune the pore structure. The sintering temperature is moderate and the time is shortened, which can improve production efficiency while ensuring molding quality.

[0037] (2) Same as step (2) in Example 1.

[0038] (3) Same as step (3) in Example 1.

[0039] (4) Same as step (4) in Example 1.

[0040] Example 3 This embodiment provides a method for preparing a porous polyimide-solid oil storage material, which is basically the same as that in Example 1. The preparation method includes the following steps: (1) Same as step (1) in Example 1.

[0041] (2) Low-density polyethylene solid oil powder with a particle size of 1000-1500 nm and semi-synthetic lubricating oil were added to a stirred tank at a weight ratio of 10:90. The mixture was stirred at 400 r / min for 3 hours under heating conditions at 50°C to allow the polyethylene solid oil powder to fully swell and be uniformly dispersed in the lubricating oil, forming a homogeneous and stable liquid phase mixture. In this embodiment, the proportion of solid oil powder was reduced and the particle size was increased, making it suitable for applications requiring moderate oil content but high mechanical strength of the solid oil; the semi-synthetic lubricating oil combines the economic advantages of mineral oil and the performance advantages of synthetic oil.

[0042] (3) The porous polyimide matrix obtained in step (1) is completely immersed in the liquid phase mixture prepared in step (2), placed in a vacuum impregnation tank, and evacuated to a pressure of 10 kPa and maintained for 8 hours to allow the liquid phase mixture to fully penetrate into the pores, thereby obtaining the pre-made oil storage material. This embodiment uses a lower vacuum degree and a longer holding time to adapt to the semi-synthetic oil system with higher viscosity and to avoid excessive volatilization of light components of the oil under high vacuum.

[0043] (4) The pre-formed oil storage material obtained in step (3) is placed in a forced-air drying oven and heated and cured at 165°C for 3 hours. After cooling to room temperature, the porous polyimide-solid oil storage material is obtained. In this embodiment, the curing temperature is increased to adapt to the melting characteristics of low-density polyethylene and ensure full curing and molding.

[0044] Example 4 This embodiment provides a method for preparing a porous polyimide-solid oil storage material, which is basically the same as that in Example 1. The preparation method includes the following steps: (1) Same as step (1) in Example 1.

[0045] (2) High-density polyethylene solid oil powder with a particle size of 800-1200 nm and fully synthetic lubricating oil were added to a stirred tank at a weight ratio of 30:70. The mixture was stirred at 400 r / min for 2 hours under heating conditions of 70°C to allow the polyethylene solid oil powder to fully swell and be uniformly dispersed in the lubricating oil, forming a homogeneous and stable liquid phase mixture. In this embodiment, the proportion of solid oil powder was increased to obtain a higher solid oil content; high-density polyethylene was used, which has higher crystallinity and better mechanical strength, which helps to improve the structural stability of the solid oil; and fully synthetic lubricating oil has better high-temperature stability and oxidation resistance, making it suitable for extreme working conditions.

[0046] (3) The porous polyimide matrix obtained in step (1) is completely immersed in the liquid phase mixture prepared in step (2), placed in a vacuum impregnation tank, and evacuated to a pressure of 1 kPa and maintained for 4 hours to allow the liquid phase mixture to fully penetrate into the pores, thereby obtaining the prefabricated oil storage material. In this embodiment, a higher vacuum degree and a shorter holding time are used to accelerate pore degassing, improve impregnation efficiency, and shorten the process cycle.

[0047] (4) The pre-made oil storage material obtained in step (3) is placed in a forced-air drying oven and heated and cured at 180°C for 1 hour. After cooling to room temperature, the porous polyimide-solid oil storage material is obtained. In this embodiment, the curing temperature is increased to meet the high melting point requirement of high-density polyethylene.

[0048] Example 5 This embodiment provides a method for preparing a porous polyimide-solid oil storage material, the preparation method comprising the following steps: (1) Polyimide powder and polytetrafluoroethylene powder are mixed evenly in a high-speed mixer at a weight ratio of 90:10, and then placed into a custom mold. The mixture is cold-pressed under a pressure of 20 MPa to obtain a blank. After demolding, the blank is removed and placed in a PTFE sintering furnace. It is then sintered at 380°C for 15 minutes to obtain a porous polyimide matrix. In this embodiment, the amount of PTFE powder added is the highest, the sintering temperature is the highest, and the sintering time is the shortest. This results in a porous polyimide matrix with higher porosity and larger pore size, which is suitable for applications with extremely high oil storage requirements.

[0049] (2) Ultra-high molecular weight polyethylene solid oil powder with a particle size of 500-1000 nm and a mineral oil-fully synthetic oil mixed lubricant (mineral oil to fully synthetic oil weight ratio of 50:50) were added to a stirred tank at a weight ratio of 25:75. The mixture was stirred at 550 r / min for 3.5 h under heating conditions of 65 °C to allow the polyethylene solid oil powder to fully swell and be uniformly dispersed in the mixed lubricant, forming a homogeneous and stable liquid phase mixture. In this embodiment, ultra-high molecular weight polyethylene is used, which has extremely high molecular weight and excellent wear resistance, and can significantly improve the durability of solid oil; the mixed lubricant takes into account both economy and high performance.

[0050] (3) The porous polyimide matrix obtained in step (1) is completely immersed in the liquid phase mixture prepared in step (2), placed in a vacuum impregnation tank, and vacuumed to a pressure of 3 kPa and maintained for 7 hours to allow the liquid phase mixture to fully penetrate into the pores and obtain the pre-made oil storage material.

[0051] (4) Place the pre-made oil storage material obtained in step (3) in a blower drying oven and heat it at 170°C for 2-4 hours. After cooling to room temperature, the porous polyimide-solid oil storage material is obtained.

[0052] Verification Example The porous polyimide-solid oil storage material obtained in Example 1 was compared with the existing simple porous polyimide oil storage material through a centrifugal oil-spraying test. The apparatus for the centrifugal oil-spraying test is as follows: Figure 3 As shown in Table 1, the actual measurement results are as follows.

[0053] Table 1

[0054] Note: (i) The porosity of the porous polyimide-solid oil storage material obtained in Example 1 is 35%.

[0055] (ii) The existing product, namely the simple porous polyimide oil storage material, has a porosity of 18%.

[0056] (iii) a indicates that the porous polyimide-solid oil storage material obtained in Example 1, after being subjected to an oil-spraying test at room temperature (25°C) and 6000 r / min for 120 min, only 0.2% of the total oil volume was lost inside the storage material, with a retention rate as high as 99.8%. The numerical meanings of other test results are interpreted similarly.

[0057] As shown in Table 1: (1) Under all test conditions, the oil retention rate of the porous polyimide-solid oil storage material of Example 1 was significantly higher than that of existing products. At room temperature and 6000 r / min, the oil retention rate of Example 1 was 99.8%, while that of existing products was only 93.85%, an improvement of 5.95 percentage points; at room temperature and 12000 r / min, the oil retention rate of Example 1 was 99.3%, while that of existing products was only 82.31%, an improvement of nearly 17 percentage points, indicating that the oil storage material of the present invention has obvious advantages in oil locking under high-speed conditions.

[0058] (2) As the rotational speed increases from 6000 r / min to 12000 r / min, the oil retention rate of existing products decreases significantly, from 93.85% to 82.31% at room temperature (a decrease of 11.54 percentage points) and from 75.16% to 68.27% at 60°C (a decrease of 6.89 percentage points). In contrast, the oil retention rate of Example 1 decreases only slightly, from 99.8% to 99.3% at room temperature (a decrease of only 0.5 percentage points) and from 98.6% to 97.9% at 60°C (a decrease of only 0.7 percentage points). This fully demonstrates that the oil storage material of the present invention has extremely low sensitivity to changes in rotational speed and exhibits excellent high-speed stability.

[0059] (3) Increased temperature has an adverse effect on the oil retention rate of both materials, but the effect is more significant on the existing product. At 6000 r / min, when the temperature rises from 25°C to 60°C, the oil retention rate of the existing product decreases from 93.85% to 75.16%, a decrease of 18.69 percentage points; while in Example 1, it only decreases from 99.8% to 98.6%, a decrease of only 1.2 percentage points. This indicates that the oil storage material of the present invention has better high-temperature oil-locking performance and can adapt to higher temperature working environments.

[0060] (4) It is worth noting that the porosity (35%) of the porous polyimide matrix in Example 1 is much higher than that of the existing products (18%), that is, the oil content of Example 1 is significantly higher than that of the existing products; under the premise of higher oil content, the oil retention rate of Example 1 is actually higher, which directly proves that the present invention has successfully broken through the inherent contradiction of "high porosity and low oil retention rate" in traditional porous materials, and achieved the unity of high oil content and high oil retention rate.

[0061] In summary, the porous polyimide-solid oil storage material of the present invention exhibits oil retention performance far superior to existing products under different temperature and speed conditions, especially under high-speed and high-temperature conditions. It can effectively solve the problem of rapid oil ejection and failure of traditional thin-oil lubricated porous polyimide materials under high-speed operation, and has important engineering application value.

[0062] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for preparing a porous polyimide-solid oil storage material, characterized in that, The preparation method includes the following steps: (1) The polyimide powder is first pressed and then sintered to obtain porous polyimide; (2) The solid oil powder and lubricating oil are stirred and mixed to obtain a liquid mixture; (3) The porous polyimide is immersed in the liquid phase mixture and a vacuum is applied to allow the liquid phase mixture to enter the pores of the porous polyimide, thereby obtaining a prefabricated oil storage material. (4) The prefabricated oil storage material is cured to obtain the porous polyimide-solid oil storage material.

2. The method for preparing the porous polyimide-solid oil storage material according to claim 1, characterized in that, In step (1), polyimide powder and lubricant are loaded into a mold and pressed to form a blank; then the blank is taken out and placed in a PTFE sintering furnace and sintered at 365-380℃ for 15-35 minutes to form a porous polyimide. The lubricant is polytetrafluoroethylene powder, and the weight ratio of the polyimide powder to the polytetrafluoroethylene powder is 90-95:10-5.

3. The method for preparing the porous polyimide-solid oil storage material according to claim 1, characterized in that, In step (2), the solid oil powder and lubricating oil are stirred and mixed at a weight ratio of 10-30:90-70 to obtain a liquid mixture; The solid oil powder is polyethylene solid oil powder, and the particle size of the polyethylene solid oil powder is 500-1500 nm. The lubricating oil is one or a combination of two or more of mineral oil, semi-synthetic oil, and fully synthetic oil.

4. The method for preparing the porous polyimide-solid oil storage material according to claim 1, characterized in that, In step (3), the porous polyimide is immersed in the liquid phase mixture, and a vacuum is drawn to a pressure of 1-10 kPa and maintained for 4-8 hours, so that the liquid phase mixture enters the pores of the porous polyimide to obtain the prefabricated oil storage material.

5. The method for preparing the porous polyimide-solid oil storage material according to claim 1, characterized in that, In step (4), the pre-made oil storage material is cured at 150-180°C to obtain the porous polyimide-solid oil storage material.

6. The porous polyimide-solid oil storage material obtained by the preparation method according to any one of claims 1-5.

7. The porous polyimide-solid oil storage material according to claim 6, characterized in that, The porous polyimide-solid oil storage material comprises porous polyimide material and solid oil; wherein: The solid oil material is embedded inside the pores of the porous polyimide material.

8. The porous polyimide-solid oil storage material according to claim 7, characterized in that, The porous polyimide material has a porosity of 25-50% and a pore diameter of 2.5-3.5 μm; The solid oil material has an oil content of 70-90% and a pore diameter of 0.5-1.5 μm.

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