Hollow aramid aerogel fiber having hierarchical pore structure, and preparation method therefor and use thereof

Abstract

Disclosed in the present application are a hollow aramid aerogel fiber having a hierarchical pore structure, and a preparation method therefor and the use thereof. The preparation method comprises: simultaneously extruding a spinning solution A and a spinning solution B into a coagulating bath by using a coaxial wet spinning method to perform in-situ dynamic sol-gel transition, wherein the spinning solution A is used as a shell spinning solution and the spinning solution B is used as a core spinning solution, followed by specific drying to obtain a hollow aramid aerogel fiber having a hierarchical pore structure; and the central part of the hollow aramid aerogel fiber having a hierarchical pore structure is of a hollow structure, and the fiber wall is of the hierarchical pore structure. The hollow aramid aerogel fiber having a hierarchical pore structure prepared in the present application has the characteristics of large specific surface area and high porosity; the inner diameter, outer diameter and wall thickness of the fiber, and the morphology and size distribution of pores in the fiber wall can be adjusted and controlled; the preparation method is universal, involves a simple preparation process, and is easily applied to large-scale production.

Description

Hollow aramid aerogel fiber with multi-level pore structure and preparation method and application thereof

[0001] The present application is based on and claims priority to the Chinese patent application No. 2024113758302, filed on September 29, 2024, and entitled "Hollow aramid aerogel fiber with multi-level pore structure and preparation method and application thereof", which is incorporated by reference herein in its entirety. TECHNICAL FIELD

[0002] The present application belongs to the technical field of nanoporous materials and functional fibers, in particular to the technical field of aerogel fibers, and specifically relates to a hollow aramid aerogel fiber with multi-level pore structure and a preparation method and application thereof. BACKGROUND

[0003] Hollow fiber is a kind of fiber material with a tubular cavity in the axial direction. The cavity of the hollow fiber can provide a large amount of stationary air, which not only increases the bulkiness of the fiber and reduces the density of the fiber, but also improves its warmth and moisture permeability. In addition, the hollow fiber also has high mechanical strength, good oxidation resistance, excellent filtration precision, high flux, acid and alkali resistance, and other advantages, which endows the hollow fiber with many unique properties and applications. For example, in the textile field, hollow fibers can be used to make winter clothes, bedding and cushioning pads, etc.; in the field of environmental treatment and water resource treatment, hollow fibers can be used as microfiltration, ultrafiltration, dialysis, gas separation, reverse osmosis and evaporation osmotic devices, etc.; in the biomedical field, hollow fibers can be used for artificial kidney, artificial lung, hemodialysis, drug separation and purification, in-vivo drug activity screening, and other medical devices. Obviously, hollow fibers have wide applications in water treatment, petroleum chemical industry, medicine, biology, food, electronics, energy, air pollution control, and aerospace, military industry, etc.

[0004] Although hollow fibers exhibit multifunctionality and high efficiency in different fields, they still have a series of technical problems, such as: (1) low porosity and small specific surface area, which leads to the need to improve the membrane flux; (2) the pore structure is the key to the performance of hollow fibers, but the current control method of pore structure is relatively complex and the effect is still not ideal; (3) currently, the materials applied to hollow fibers include polyvinylidene fluoride, polyether sulfone, polypropylene, polyethylene, polytetrafluoroethylene, etc., and new types of hollow fiber membrane materials need to be developed to be suitable for more complex environments; (4) the production cost is relatively high, and the energy consumption in the production process is large.

[0005] Aerogel is a kind of solid nanomaterial with three-dimensional network structure, which has ultra-high porosity, large specific surface area, ultra-low density and excellent mechanical properties and serviceability, and has important application value in many fields such as textiles, environment, energy conversion and storage, thermal protection, infrared stealth and electromagnetic shielding. The excellent performance of aerogel and its flexible preparation method can be applied to the manufacture of hollow fibers, which can solve the technical problems of hollow fibers to some extent. For example, Chinese invention patent CN118127654A discloses a kind of hollow aerogel fiber and its preparation method at normal temperature and pressure. The patent provides a preparation method for preparing hollow aerogel fiber, which includes preparing a hollow fiber with a porous aerogel structure by synchronous non-solvent phase separation inside and outside the fiber at normal temperature and pressure. The coaxial extrusion equipment is used, the inner core uses non-solvent core liquid, and the outer layer uses polymer / solvent solution. Then, it is injected into the coagulation bath at the same time to coagulate and form. After drying, the hollow aerogel fiber is obtained. However, the material prepared by this method has mostly closed pores, and the porosity of the material is relatively low, which is not conducive to the performance of the hollow fiber. For another example, Chinese invention patent CN110607577A discloses a kind of graphene aerogel hollow fiber, its preparation method and application. However, the graphene aerogel material is usually brittle, and the pore structure, morphology and distribution cannot be controlled, which makes it difficult to solve the problems of high selectivity and high throughput at the same time, and the application range is narrow. Further, Chinese invention patent CN117512809A discloses a kind of core-shell structure aramid / fiber cellulose aerogel fiber and its preparation method. The aramid fiber is dissolved in a non-polar solvent in an alkaline environment to prepare a shell layer spinning solution. The nanocellulose powder is placed in deionized water and treated by ultrasonic dispersion to prepare a core layer spinning solution. After wet spinning, coagulation and winding, the core-shell structure aramid / fiber cellulose aerogel fiber is prepared by replacing and drying in different concentration gradients of solvent. The aerogel fiber prepared by the invention has a double-layer structure. The core layer fiber has the characteristics of rich pores, ultra-low density and ultra-high specific surface area. The shell layer fiber has the characteristics of dense surface, high temperature resistance and high strength. However, the method produces core-shell fibers, and the range of fiber pore control is small and difficult.

[0006] Based on the above, the present application develops a new kind of preparation method of hollow aramid aerogel fiber with multi-level pore structure on the basis of the existing technology. Based on the coaxial wet spinning technology, the multi-level pore structure and pore shape are controlled by adjusting the spinning solution and spinning process parameters to meet the needs of high selectivity and high throughput in actual application. SUMMARY

[0007] The application aims to provide a multi-level pore structure hollow aramid aerogel fiber and a preparation method and application thereof to overcome the deficiencies in the prior art. By adjusting the inner diameter, outer diameter and wall thickness of the fiber and the pore size, pore morphology and pore size distribution on the fiber wall, the differential pressure, flux and selectivity of the medium through the tube wall are adjusted to obtain the required hollow aramid aerogel fiber and improve and expand the use performance and application range of the hollow aerogel fiber in the prior art.

[0008] To achieve the above-mentioned application purposes, the application adopts the following technical solutions.

[0009] As the first aspect of the application, the application provides a preparation method of a multi-level pore structure hollow aramid aerogel fiber, which comprises the following steps:

[0010] at least mixing aramid fibers and a first solvent uniformly and taking them as a spinning solution A;

[0011] providing a spinning solution B;

[0012] adopting a coaxial spinning method, the spinning solution A and the spinning solution B are injected from two inlets respectively and then "mixed" at the needle, a sol-gel transition occurs under the condition of a coagulation bath, the spinning solution A is coated on the surface of the spinning solution B; then through solvent replacement, drying and post-processing, the multi-level pore structure hollow aramid aerogel fiber is obtained.

[0013] The coagulation bath is a static coagulation bath, but the spinning solution is extruded into the static coagulation bath in a dynamic form, the sol-gel transition occurs while the spinning solution is extruded, that is, an in-situ dynamic sol-gel transition, the aramid gel fiber with a hollow structure is obtained; then through solvent replacement-drying treatment, the multi-level pore structure hollow aramid aerogel fiber is obtained.

[0014] Especially, the hollow aramid aerogel fiber obtained by the above technical solution has a multi-level pore structure; and through adjustment of raw materials and process parameters, aerogel fibers with various pore levels, different pore distributions and different morphologies can be obtained, and the problems of high selectivity and high flux of aerogel materials are solved.

[0015] Further, the aramid fibers are any one or a combination of two or more of para-aramid, meta-aramid, aramid III, aramid copolymer fiber, poly-p-phenylene terephthalamide, poly-p-aramid benzimidazole fiber and heterocyclic aromatic polyamide fiber.

[0016] Further, the first solvent comprises any one or a combination of two or more of azomethylnitrone, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, methanol, water, acetone, ethanol and concentrated sulfuric acid.

[0017] Further, the concentration of the aerogel precursor is 0.1-30 wt%.

[0018] Further, the spinning solution B includes a second solvent with / without adding a solute.

[0019] Further, the solute includes any one or a combination of two or more of hydroxymethyl cellulose, hydroxyethyl cellulose, sodium alginate, gelatin, polyvinyl alcohol, carbomer, and agarose.

[0020] Further, the second solvent includes any one or a combination of two or more of water, ethanol, acetone, N-methyl pyrrolidone, ethyl acetate, acetonitrile, dimethyl sulfoxide, glycerol, dimethyl silicone oil, and N,N-dimethylformamide.

[0021] Further, the coagulation bath includes a third solvent with / without adding an auxiliary component.

[0022] Further, the third solvent includes any one or a combination of two or more of water, ethanol, acetone, dimethyl sulfoxide, N-methyl pyrrolidone, ethyl acetate, dimethyl silicone oil, N,N-dimethylformamide, glycerol, and t-butyl alcohol.

[0023] Further, the auxiliary component includes any one or a combination of two or more of calcium chloride, ferric chloride, silver ion, copper ion, hydrochloric acid, sulfuric acid, and acetic acid.

[0024] Further, in the coaxial needle used in the coaxial wet spinning method, the outer diameter of the inner needle of the coaxial needle is 100 μm-1.5 mm, the inner diameter of the outer needle of the coaxial needle is 150 μm-2 mm, and the distance between the outer diameter of the inner needle and the inner diameter of the outer needle is 50 μm-1000 μm.

[0025] Further, the extrusion speed is 50-1000 μL / min.

[0026] Further, the solvent replacement includes immersing the hollow aramid gel fiber into a replacement solvent for replacement.

[0027] Further, the replacement solvent is one or a combination of two or more of water, ethanol, t-butyl alcohol, n-hexane, hexafluoroisopropanol, cyclohexane, and acetone.

[0028] Further, the drying treatment includes any one or a combination of two or more of freeze drying, supercritical fluid drying, and atmospheric drying.

[0029] As a preferred embodiment, the spinning solution A further includes an additive.

[0030] Preferably, the additive is a first additive, or a combination of the first additive and a second additive.

[0031] Preferably, the first additive is any one or a combination of two or more of potassium tert-butoxide, potassium hydroxide, sodium hydride, potassium methoxide, butyllithium, sodium ethoxide, potassium ethoxide, sodium hydroxide.

[0032] Preferably, the second additive is any one or a combination of two or more of polyethylene glycol, polyacrylonitrile, polyvinyl alcohol, polyvinylpyrrolidone, dibutyl phthalate, glycerol.

[0033] Preferably, the mass ratio of the first additive to aramid fiber is 0.1-1:1.

[0034] Preferably, the mass ratio of the second additive to aramid fiber is 0.2-2:1.

[0035] As one of the purposes of the application, the application further provides a modified hollow aramid aerogel fiber with a hierarchical porous structure, which is prepared by post-treating the aforementioned hollow aramid aerogel fiber with a hierarchical porous structure.

[0036] Further, the post-treatment includes any one or a combination of two or more of heat treatment, hydrophobization treatment, and filling modification.

[0037] Preferably, the method of heat treatment includes directly placing the hollow aramid aerogel fiber with a hierarchical porous structure in a tube furnace, and treating it at a high temperature for 30 min-6 h under a specific atmosphere.

[0038] Preferably, the specific atmosphere is any one of nitrogen, argon, and air.

[0039] Preferably, the heat treatment temperature is 80-450℃.

[0040] Preferably, the method of hydrophobization treatment includes directly immersing the hollow aramid aerogel fiber with a hierarchical porous structure in a hydrophobic coating solution for 3 s-1 h, and then taking it out and vacuum drying it at room temperature and pressure or at 30-150℃ for 10 min-72 h; the content of the hydrophobic substance in the hydrophobic coating solution is 0.05-20 wt%.

[0041] Preferably, the hydrophobic substance includes any one or a combination of two or more of fluorocarbon resin, fluorocarbon modified resin, silicone resin, perfluoroalkane, and polydimethylsiloxane.

[0042] Preferably, the method of filling modification includes immersing the hollow aramid aerogel fiber with a hierarchical porous structure in a functional liquid material for 30 min-24 h, and then naturally placing it after taking it out.

[0043] Preferably, the functional liquid comprises any one or a combination of two or more of polyethylene glycol, liquid paraffin, polyhydric alcohol, dimethyl silicone oil, perfluoropolyether.

[0044] As one of the purposes of the application, the application also provides a multi-level porous hollow aramid aerogel fiber. The middle part of the fiber is a hollow structure, and the fiber wall is a multi-level porous structure. The outer diameter of the multi-level porous hollow aerogel fiber is 150 μm to 2 mm, the inner diameter is 100 μm to 1.5 mm, the wall thickness is 50 μm to 1000 μm, and the length-diameter ratio is greater than 10.

[0045] As a preferred embodiment, the multi-level porous structure comprises a large pore channel, a mesopore channel, and a micropore channel.

[0046] As a preferred embodiment, the multi-level porous structure comprises a large pore channel, a mesopore channel, and a micropore channel.

[0047] Preferably, the multi-level porous structure comprises a large pore channel greater than 10 μm, a mesopore channel of 50 nm to 10 μm, a mesopore channel of 2 nm to 50 nm, and a micropore channel less than 2 nm.

[0048] Further, the large pore channel is radially arranged perpendicular to the inner and outer walls of the fiber.

[0049] More preferably, the shape of the large pore channel is a finger-shaped through-hole structure, or a needle-shaped or half-finger-shaped half-through-hole structure.

[0050] Preferably, the through-hole structure is radially arranged from the inner wall to the outer wall.

[0051] Preferably, the half-through-hole structure is located on one side of the fiber wall, or on the inner and outer sides of the fiber wall and has a symmetrical structure.

[0052] In some specific embodiments, the multi-level porous hollow aramid aerogel fiber has a porosity of 60% to 99% and a specific surface area of 10 to 2000 m 2 / g.

[0053] The types, addition ratios, and process parameters of raw materials in the preparation process can be adjusted according to actual needs to prepare a multi-level porous hollow aramid aerogel fiber with a large pore channel radially arranged. The large pore channel can be a finger-shaped through-hole structure radially arranged, a needle-shaped or half-finger-shaped half-through-hole structure radially arranged on one side of the fiber wall, or a half-finger-shaped half-through-hole structure radially arranged symmetrically on the inner and outer sides of the fiber wall, and so on, so as to obtain an aerogel fiber material with different fluxes and different multi-level porous structures according to actual needs.

[0054] The aramid aerogel fiber prepared by the above scheme has a multi-level pore, a hollow structure, and the inner diameter, outer diameter and wall thickness of the fiber and the pore size, pore morphology and pore size distribution on the fiber wall can be controlled. In addition, by adjusting the preparation process parameters, the differential pressure, flux and selectivity of the fiber wall can also be controlled to obtain a hollow aramid aerogel fiber with a multi-level pore structure meeting the requirements and meeting the different needs of various fields; specifically, the use of the foregoing multi-level pore structure hollow aramid aerogel fiber or the modified multi-level pore structure hollow aramid aerogel fiber includes applications in the fields of oxygenators, artificial kidneys, water-oil separation, filtration, seawater desalination, water treatment, thermal insulation, etc.

[0055] Based on the application requirements of different fields, the method provided by the present application has great versatility, and the preparation process is simple and easy to realize large-scale production.

[0056] Compared with the prior art, the present application has at least the following beneficial effects:

[0057] (1) The present application adopts a coaxial wet spinning method, and by adjusting the raw materials and process parameters, a hollow aramid aerogel fiber with various pore levels, different pore distributions and different pore morphologies can be obtained, thereby solving the problems of high selectivity and high flux of aerogel materials.

[0058] (2) The method for preparing a multi-level pore structure hollow aramid aerogel fiber provided by the present application does not require complex synthesis technology, and has a simple process, low energy consumption, low production cost and is suitable for large-scale production and application.

[0059] (3) The multi-level pore structure hollow aramid aerogel fiber provided by the present application has a hollow structure in the middle and a multi-level pore structure in the fiber wall, wherein the multi-level pore structure includes a large pore channel, a secondary large pore channel, a mesopore channel and a micropore channel; the obtained multi-level pore structure hollow aramid aerogel fiber has a large specific surface area and high porosity, and the pore size, pore morphology and pore size distribution on the fiber wall can be controlled as needed, and in particular, the porous structure has strong designability.

[0060] (4) The multi-level pore structure hollow aramid aerogel fiber provided by the present application can be heat treated, hydrophobized and filled according to the use environment, and can be used in the fields of oxygenators, artificial kidneys, water-oil separation, filtration, seawater desalination, water treatment, thermal insulation, etc., greatly expanding and improving the application range and use performance of aerogels and hollow fibers. BRIEF DESCRIPTION OF DRAWINGS

[0061] FIG. 1 is an optical photograph of the multi-level pore structure hollow aramid aerogel fiber prepared by the present application.

[0062] FIG. 2 shows a scanning electron microscope image of the multi-level pore structure hollow aramid aerogel fiber prepared by Example 1 of the present application.

[0063] Fig. 3 is a partial enlarged view of Fig. 2.

[0064] Fig. 4 shows a scanning electron microscope image of the multi-porous hollow aramid aerogel fiber prepared in Embodiment 2 of the present application.

[0065] Fig. 5 is a partial enlarged view of Fig. 4.

[0066] Fig. 6 shows a scanning electron microscope image of the multi-porous hollow aramid aerogel fiber prepared in Embodiment 3 of the present application.

[0067] Fig. 7 shows a scanning electron microscope image of the multi-porous hollow aramid aerogel fiber prepared in Embodiment 4 of the present application.

[0068] Fig. 8 shows a scanning electron microscope image of the multi-porous hollow aramid aerogel fiber prepared in Embodiment 5 of the present application.

[0069] Fig. 9 shows a scanning electron microscope image of the multi-porous hollow aramid aerogel fiber prepared in Embodiment 6 of the present application.

[0070] Fig. 10 shows a partial enlarged scanning electron microscope image of the multi-porous hollow aramid aerogel fiber prepared in Embodiment 7 of the present application.

[0071] Fig. 11 shows a nitrogen adsorption-desorption curve of the multi-porous hollow aramid aerogel fiber prepared in Embodiment 8 of the present application.

[0072] Fig. 12 shows a pore size distribution curve of the multi-porous hollow aramid aerogel fiber prepared in Embodiment 8 of the present application.

[0073] Fig. 13 shows a tensile curve of the multi-porous hollow aramid aerogel fiber prepared in Embodiment 9 of the present application.

[0074] Fig. 14 shows the water contact angle of the multi-porous hollow aramid aerogel fiber before and after hydrophobic modification prepared in Embodiment 10 of the present application. DETAILED DESCRIPTION

[0075] In order to make the purpose, technical scheme and advantages of the embodiments of the present application more clear, the technical scheme in the embodiments of the present application is described clearly and completely below. Obviously, the described embodiments are only some embodiments of the present application, but not all the embodiments.

[0076] Referring to Fig. 1, the multi-porous hollow aramid aerogel fiber provided by the present application has a hollow structure in the middle part and a multi-porous structure in the fiber wall, wherein the multi-porous structure includes macro-porous channels, sub-macro-porous channels, meso-porous channels and micro-porous channels.

[0077] The preparation method mainly comprises: uniformly mixing at least aramid fibers and a first solvent to obtain a spinning solution A; providing a spinning solution B; simultaneously extruding the spinning solution A and the spinning solution B into a coagulation bath through a coaxial wet spinning method, and the spinning solution undergoes dynamic sol-gel transformation in situ in the coagulation bath to obtain hollow aramid gel fibers; and then through solvent replacement, drying and post-processing, the hollow aramid aerogel fibers with a hierarchical porous structure are obtained.

[0078] The technical scheme, the implementation process and principles thereof will be further explained as follows.

[0079] An aspect of the embodiment of the present application provides a preparation method of hollow aramid aerogel fibers with a hierarchical porous structure, which comprises:

[0080] uniformly mixing at least aramid fibers and a first solvent to obtain a spinning solution A;

[0081] providing a spinning solution B;

[0082] simultaneously extruding the spinning solution A and the spinning solution B into a coagulation bath through a coaxial wet spinning method, and the spinning solution undergoes dynamic sol-gel transformation in situ in the coagulation bath to obtain hollow aramid gel fibers;

[0083] and then through solvent replacement, drying and post-processing, the hollow aramid aerogel fibers with a hierarchical porous structure are obtained.

[0084] In some preferred embodiments, the aramid fibers comprise any one or a combination of two or more of para-aramid, meta-aramid, aramid III, aramid copolymer fiber, poly-p-phenylene terephthalamide, poly-p-aramid benzimidazole fiber, and heterocyclic aromatic polyamide fiber, but are not limited thereto.

[0085] Further, the first solvent comprises any one or a combination of two or more of azomethylnitrone, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, methanol, water, acetone, ethanol, concentrated sulfuric acid, but is not limited thereto.

[0086] Further, in the spinning solution A, the concentration of the aramid fibers is 0.1-30 wt%.

[0087] The spinning solution A further comprises an additive.

[0088] Further, the additive is a first additive, or a combination of the first additive and a second additive.

[0089] Further, the first additive is any one or a combination of two or more of potassium tert-butoxide, potassium hydroxide, sodium hydride, potassium methoxide, butyl lithium, sodium ethoxide, potassium ethoxide, and sodium hydroxide.

[0090] Further, the second additive is any one of polyethylene glycol, polyacrylonitrile, polyvinyl alcohol, polyvinylpyrrolidone, dibutyl phthalate, glycerol, or a combination of two or more thereof.

[0091] Further, the mass ratio of the first additive to aramid fiber is 0.1-1:1.

[0092] Further, the mass ratio of the second additive to aramid fiber is 0.2-2:1.

[0093] In some preferred embodiments, the second solvent with / without adding solute is included in the spinning solution B.

[0094] Further, the solute includes any one of hydroxymethyl cellulose, hydroxyethyl cellulose, sodium alginate, gelatin, polyvinyl alcohol, carbomer, agarose, or a combination of two or more thereof, but is not limited thereto.

[0095] Further, the second solvent includes any one of water, ethanol, acetone, azamethylpyrrolidone, ethyl acetate, acetonitrile, dimethyl sulfoxide, glycerol, dimethyl silicone oil, N,N-dimethylformamide, or a combination of two or more thereof, but is not limited thereto.

[0096] In some preferred embodiments, the coagulation bath includes a third solvent with / without adding an auxiliary component.

[0097] Further, the third solvent includes any one of water, ethanol, acetone, dimethyl sulfoxide, azamethylpyrrolidone, ethyl acetate, dimethyl silicone oil, N,N-dimethylformamide, glycerol, tert-butyl alcohol, or a combination of two or more thereof, but is not limited thereto.

[0098] Further, the auxiliary component includes any one of calcium chloride, ferric chloride, silver ion, copper ion, hydrochloric acid, sulfuric acid, acetic acid, or a combination of two or more thereof, but is not limited thereto.

[0099] In some preferred embodiments, the coaxial needle used in the coaxial wet spinning method has an inner needle outer diameter of 100 μm-1.5 mm, an outer needle inner diameter of 150 μm-2 mm, and a distance between the inner needle outer diameter and the outer needle inner diameter of 50 μm-1000 μm.

[0100] Further, the extrusion speed is 50-1000 μL / min.

[0101] In some preferred embodiments, the displacement solvent is one or a combination of two or more of water, ethanol, tert-butyl alcohol, n-hexane, hexafluoroisopropyl alcohol, cyclohexane, and acetone, but is not limited thereto.

[0102] In some preferred embodiments, the drying process includes any one or a combination of two or more of freeze drying, supercritical fluid drying, and atmospheric drying, but is not limited thereto.

[0103] Further, the cold trap temperature of the freeze drying is -80 to 15℃, and the vacuum degree is less than 0.1 kPa.

[0104] Further, the supercritical fluid in the supercritical fluid drying includes any one of supercritical CO2, supercritical methanol, and supercritical ethanol.

[0105] Another aspect of the embodiments of the present application also provides a post-treatment of the multi-level porous structure hollow aramid aerogel fiber.

[0106] Preferably, the post-treatment includes any one of heat treatment, hydrophobic treatment, filling modification, etc.

[0107] Specifically, the post-treatment method can be any one of the following methods:

[0108] (1) The multi-level porous structure hollow aramid aerogel fiber is directly placed in a tube furnace, and is treated at a high temperature for 30 min to 6 h under a specific atmosphere; the atmosphere is one of nitrogen, argon, and air; the heat treatment temperature is 80 to 450℃.

[0109] (2) The multi-level porous structure hollow aramid aerogel fiber is directly immersed in a hydrophobic coating solution for 3 s to 1 h, and then is taken out and vacuum dried at room temperature and pressure or 30 to 150℃ for 10 min to 72 h; the content of the hydrophobic substance in the hydrophobic coating solution is 0.05 to 20 wt%; the hydrophobic substance includes any one or a combination of two or more of fluorocarbon resin, fluorocarbon modified resin, silicone resin, perfluoroalkane, and polydimethylsiloxane, but is not limited thereto.

[0110] (3) The multi-level porous structure hollow aramid aerogel fiber is immersed in a functional liquid material for 30 min to 24 h, and is naturally placed after being taken out; the functional liquid includes any one or a combination of two or more of polyethylene glycol, liquid paraffin, polyol, dimethyl silicone oil, and perfluoropolyether, but is not limited thereto.

[0111] Another aspect of the embodiments of the present application also provides a multi-level porous structure hollow aramid aerogel fiber, the middle part of the multi-level porous structure hollow aramid aerogel fiber is a hollow structure, and the fiber wall is a multi-level porous structure; the multi-level porous structure includes a large pore channel, a secondary large pore channel, a mesopore channel, and a micropore channel; the large pore channel is arranged perpendicular to the inner and outer walls of the fiber.

[0112] In some preferred embodiments, the hollow aramid aerogel fiber with the multi-level pore structure has an outer diameter of 150 μm to 2 mm, an inner diameter of 100 μm to 1.5 mm, a wall thickness of 50 μm to 1000 μm, and a length-diameter ratio greater than 10, but is not limited thereto.

[0113] Further, the hollow aramid aerogel fiber with the multi-level pore structure has a porosity of 60% to 99%, a specific surface area of 10 to 2000 m 2 / g, but is not limited thereto.

[0114] Another aspect of the embodiments of the present application also provides an application of the aforementioned hollow aramid aerogel fiber with the multi-level pore structure or the modified hollow aramid aerogel fiber with the multi-level pore structure in the fields of oxygenators, artificial kidneys, water-oil separation, filtration, seawater desalination, water treatment, thermal insulation, etc.

[0115] Specifically, in the application, at least part of the components are made of the aforementioned hollow aramid aerogel fiber with the multi-level pore structure.

[0116] The coaxial wet spinning method provided by the present application can obtain hollow aramid aerogel fibers with various pore levels, different pore channel distributions and different pore morphologies by adjusting the raw materials and process parameters, thereby solving the problems of high selectivity and high throughput of aerogel materials.

[0117] The method for preparing the hollow aramid aerogel fiber with the multi-level pore structure provided by the present application does not require complex synthesis techniques, has a simple process, low energy consumption and low production cost, and is suitable for large-scale production and application.

[0118] The hollow aramid aerogel fiber with the multi-level pore structure provided by the present application has a hollow structure in the middle and a multi-level pore structure in the fiber wall, wherein the multi-level pore structure includes a large pore channel, a secondary large pore channel, a mesopore channel and a micropore channel. The specific surface area is large and the porosity is high, and the pore size, pore morphology and pore size distribution on the fiber wall can be controlled as needed, and the structure has extremely strong designability.

[0119] The hollow aramid aerogel fiber with the multi-level pore structure provided by the present application can be subjected to heat treatment, hydrophobization treatment and filling modification according to the use environment, and can be used in the fields of oxygenators, artificial kidneys, water-oil separation, filtration, seawater desalination, water treatment, thermal insulation, etc., greatly expanding and improving the application range and use performance of aerogels and hollow fiber membranes.

[0120] In summary, by means of the technical scheme, the preparation method of the hollow aramid aerogel fiber with a multi-level pore structure provided in the application is at least to uniformly mix aramid fibers and a solvent to serve as spinning solution A; spinning solution B is provided; the spinning solution A and the spinning solution B are simultaneously extruded into a coagulation bath by means of a coaxial wet spinning method, and the spinning solution undergoes in-situ dynamic sol-gel transformation in the coagulation bath to obtain a hollow aramid gel fiber; then, solvent replacement, drying and post-processing are performed to obtain the hollow aramid aerogel fiber with a multi-level pore structure. The hollow aramid aerogel fiber with a multi-level pore structure provided in the application can be used in the fields of oxygenators, artificial kidneys, water-oil separation, filtration, seawater desalination, water treatment, thermal insulation and the like.

[0121] The technical scheme of the application is further described in detail below by means of several embodiments in combination with the accompanying drawings. However, the selected embodiments are only used to illustrate the application and do not limit the scope of the application, and a person skilled in the art can make adjustments according to the actual situation.

[0122] Embodiment 1

[0123] The embodiment provides a preparation method of a hollow aramid aerogel fiber with a multi-level pore structure, and the specific steps include:

[0124] (1) 0.6:0.3:0.6:8.5 of para-aramid, potassium tert-butoxide, methanol, dimethyl sulfoxide by mass ratio are mixed to serve as spinning solution A, and the concentration of the para-aramid is 6wt%; 1wt% of sodium alginate / water solution is used as spinning solution B;

[0125] (2) a coaxial needle head with an inner needle diameter of 710μm and an outer needle inner diameter of 1.5mm is adopted, and the spinning solution A and the spinning solution B are mixed and then extruded into an ethanol / water coagulation bath at an extrusion speed of 700μL / min by means of a coaxial wet spinning method, so that the spinning solution undergoes in-situ dynamic sol-gel transformation in the coagulation bath to obtain a hollow aramid gel fiber;

[0126] (3) water is used as a replacement solvent, the aramid gel fiber is immersed into the replacement solvent for solvent replacement, and then freeze-drying is adopted, wherein the cold trap temperature of the freeze-drying is-8015℃, and the vacuum degree is less than 0.1kPa; finally, the hollow aramid aerogel fiber with a multi-level pore structure is obtained;

[0127] (4) the obtained fiber is heat-treated at 100℃ for 6h under a nitrogen atmosphere to obtain a modified hollow aramid aerogel fiber with a multi-level pore structure.

[0128] Referring to FIG. 1, it is a real photo of the hollow aramid aerogel fiber with a multi-level pore structure prepared in the embodiment.

[0129] Referring to FIG. 2 and FIG. 3, which are scanning electron microscope images and partial enlarged views of the hollow aramid aerogel fiber with a hierarchical porous structure prepared in the embodiment, it can be seen from the images that the obtained fiber has a hollow structure, and the fiber wall has a three-dimensional network porous structure.

[0130] Embodiment 2

[0131] The embodiment provides a preparation method of a hollow aramid aerogel fiber with a hierarchical porous structure, and the specific steps include:

[0132] (1) mixing aramid copolymer fiber, potassium methoxide, polyvinylpyrrolidone and dimethyl sulfoxide (mass ratio 0.8:0.8:1.6:6.8) as spinning solution A, and the concentration of aramid copolymer fiber is 8wt%; mixing carbomer / glycerol mixed solution (the concentration of carbomer is 0.5wt%) as spinning solution B;

[0133] (2) using a needle head with an inner needle diameter of 1.2mm and an outer needle inner diameter of 2mm, the spinning solution A and the spinning solution B are simultaneously extruded into a dilute hydrochloric acid coagulation bath at an extrusion speed of 800μL / min, and the spinning solution undergoes in-situ dynamic sol-gel transformation in the coagulation bath to obtain a hollow aramid gel fiber;

[0134] (3) using acetone as a replacement solvent, solvent replacement is performed, and then supercritical carbon dioxide drying is adopted to obtain a hollow aramid aerogel fiber with a hierarchical porous structure;

[0135] (4) the obtained fiber is heat treated at 80℃ for 3h under an argon atmosphere to obtain a modified hollow aramid aerogel fiber with a hierarchical porous structure.

[0136] FIG. 4 and FIG. 5 respectively show a scanning electron microscope image and a partial enlarged view of the hollow aramid aerogel fiber with a hierarchical porous structure obtained in the embodiment, and it can be seen from the images that the middle part of the fiber has a hollow structure, and the fiber wall has a three-dimensional network hierarchical porous structure, and the large pore channels are arranged in a radial needle-like shape.

[0137] Embodiment 3

[0138] The embodiment provides a preparation method of a hollow aramid aerogel fiber with a hierarchical porous structure, and the specific steps include:

[0139] (1) mixing poly(p-phenyleneterephthalamide), sodium hydride, polyvinyl alcohol and dimethyl sulfoxide (mass ratio 1:1:0.2:7.8) and taking as spinning solution A, and the concentration of poly(p-phenyleneterephthalamide) is 10wt%, and taking acetone as spinning solution B;

[0140] (2) using a needle head with an inner needle outer diameter of 510 μm and an outer needle inner diameter of 1 mm, the spinning solution A and the spinning solution B are simultaneously extruded into a acetone / dimethyl sulfoxide / water coagulation bath at an extrusion speed of 500 μL / min by a coaxial wet spinning method, the spinning solution undergoes in-situ dynamic sol-gel transformation in the coagulation bath to obtain hollow aramid gel fibers;

[0141] (3) solvent replacement is performed by water and anhydrous ethanol, followed by supercritical carbon dioxide drying to obtain hollow aramid aerogel fibers with a hierarchical pore structure.

[0142] (4) the fibers obtained in step (3) are heat treated at 100 ℃ for 6 h in an air atmosphere to obtain hollow aramid aerogel fibers with a modified hierarchical pore structure.

[0143] Figure 6 shows a scanning electron microscope magnified view of the fiber wall of the hollow aramid aerogel fibers with a hierarchical pore structure obtained in this embodiment, as can be seen from the figure, the fiber wall has a hierarchical pore structure, including large pore channels, secondary large pore channels, mesoporous channels and microporous channels.

[0144] Example 4

[0145] This embodiment provides a preparation method of hollow aramid aerogel fibers with a hierarchical pore structure, and the specific steps include:

[0146] (1) poly-p-aramid benzimidazole fibers, sodium hydroxide, polyethylene glycol, N,N-dimethylformamide, dimethyl sulfoxide (mass ratio 0.1:0.1:0.2:0.1:99.5) are mixed and used as the spinning solution A, the concentration of the poly-p-aramid benzimidazole fibers is 0.1 wt%, and N,N-dimethylformamide is used as the spinning solution B.

[0147] (2) using a needle head with an inner needle outer diameter of 300 μm and an outer needle inner diameter of 710 μm, the spinning solution A and the spinning solution B are simultaneously extruded into a water coagulation bath at an extrusion speed of 350 μL / min by a coaxial wet spinning method, the spinning solution undergoes in-situ dynamic sol-gel transformation in the coagulation bath to obtain hollow aramid gel fibers.

[0148] (3) solvent replacement is performed by water and tert-butyl alcohol, followed by freeze-drying to obtain hollow aerogel fibers.

[0149] (4) the obtained fibers are heat treated at 300 ℃ for 30 min in an argon atmosphere to obtain hollow aramid aerogel fibers with a modified hierarchical pore structure, which can be used in the field of water-oil separation.

[0150] Figure 7 shows a scanning electron microscope view of the hollow aramid aerogel fibers with a hierarchical pore structure obtained in this embodiment, as can be seen from the figure, the large pore channels are arranged radially in the fiber wall in a finger-like form.

[0151] Example 5

[0152] The present embodiment provides a preparation method of hollow aramid aerogel fibers with a hierarchical porous structure, and the specific steps include:

[0153] (1) Mix poly-p-phenyleneterephthalamide fibers, potassium ethoxide, polyvinylpyrrolidone, and dimethyl sulfoxide (mass ratio 0.4:0.4:0.6:8.6) as spinning solution A, and the concentration of poly-p-phenyleneterephthalamide fibers is 4wt%, and 5wt% hydroxymethyl cellulose / water solution as spinning solution B;

[0154] (2) Use a needle head with an inner needle outer diameter of 300μm and an outer needle inner diameter of 710μm, and through a coaxial wet spinning method, spin the spinning solution A and the spinning solution B into the water coagulation bath at an extrusion speed of 500μL / min, and the spinning solution undergoes in-situ dynamic sol-gel transformation in the coagulation bath to obtain hollow aramid gel fibers;

[0155] (3) Perform solvent replacement with water and acetone, and then use supercritical carbon dioxide drying to obtain hollow aramid aerogel fibers with a hierarchical porous structure.

[0156] (4) Then heat treat the obtained fibers at 450℃ for 30min under an argon atmosphere to obtain modified hollow aramid aerogel fibers with a hierarchical porous structure.

[0157] Figure 8 shows a scanning electron microscope image of the hollow aramid aerogel fibers with a hierarchical porous structure obtained in the present embodiment, and as can be seen from the figure, the large pore channels are arranged in the fiber wall in a half-finger shape on one side and radially.

[0158] Example 6

[0159] The present embodiment provides a preparation method of hollow aramid aerogel fibers with a hierarchical porous structure, and the specific steps include:

[0160] (1) Mix poly-p-phenyleneterephthalamide, sodium hydride, polyethylene glycol, ethanol, and dimethyl sulfoxide (mass ratio 0.4:0.4:0.8:0.2:8.2) as spinning solution A, and the concentration of poly-p-phenyleneterephthalamide is 4wt%, and water as spinning solution B;

[0161] (2) Use a needle head with an inner needle outer diameter of 250μm and an outer needle inner diameter of 510μm, and through a coaxial wet spinning method, spin the spinning solution A and the spinning solution B into the acetonitrile / water coagulation bath at an extrusion speed of 1000μL / min, and the spinning solution undergoes in-situ dynamic sol-gel transformation in the coagulation bath to obtain hollow aramid gel fibers;

[0162] (3) Perform solvent replacement with ethanol, and then use supercritical carbon dioxide drying to obtain hollow aramid aerogel fibers with a hierarchical porous structure.

[0163] (4) The obtained fiber is then heat treated at 80℃ for 1h under argon atmosphere to obtain the modified multi-level pore structure hollow aramid aerogel fiber which can be used as an oxygenator.

[0164] Figure 9 shows the scanning electron microscope image of the multi-level pore structure hollow aramid aerogel fiber obtained in this embodiment. As can be seen from the figure, the large pore channels are radially arranged in the fiber wall in a symmetric half-finger shape, having a multi-level pore structure.

[0165] Example 7

[0166] This embodiment provides a method for preparing a multi-level pore structure hollow aramid aerogel fiber, and the specific steps include:

[0167] (1) Para-aramid fiber, sodium ethoxide, ethanol, dimethyl sulfoxide (mass ratio of 0.2:0.2:0.2:9.4) are mixed and used as spinning solution A, the concentration of para-aramid fiber is 2wt%, and ethyl acetate is used as spinning solution B;

[0168] (2) A needle with an inner diameter of 100μm and an outer diameter of 150μm is used, and the spinning solution A and the spinning solution B are simultaneously extruded into the calcium chloride / water coagulation bath at an extrusion speed of 50μL / min by coaxial wet spinning method, and the spinning solution undergoes in-situ dynamic sol-gel transformation in the coagulation bath to obtain a hollow aramid gel fiber;

[0169] (3) Solvent replacement is carried out with water and tert-butyl alcohol in turn, and then freeze-drying is carried out to obtain a hollow aerogel fiber.

[0170] (4) The obtained fiber is then heat treated at 100℃ for 3h under argon atmosphere to obtain the modified multi-level pore structure hollow aramid aerogel fiber.

[0171] Figure 10 shows the scanning electron microscope image of the multi-level pore structure hollow aramid aerogel fiber obtained in this embodiment. As can be seen from the figure, the fiber wall has a multi-level pore structure of sub-large pore channels, mesoporous channels and microporous channels.

[0172] Example 8

[0173] This embodiment provides a method for preparing a multi-level pore structure hollow aramid aerogel fiber, and the specific steps include:

[0174] (1) Para-aramid fiber, sodium ethoxide, ethanol, dimethyl sulfoxide (mass ratio of 0.2:0.2:0.2:9.4) are mixed and used as spinning solution A, the concentration of para-aramid fiber is 2wt%, and ethyl acetate is used as spinning solution B;

[0175] (2) using a needle head with an inner needle outer diameter of 300 μm and an outer needle inner diameter of 550 μm, the spinning solution A and the spinning solution B are simultaneously extruded into a water-free calcium chloride / water coagulation bath at an extrusion speed of 500 μL / min, the spinning solution undergoes in-situ dynamic sol-gel transformation in the coagulation bath to obtain hollow aramid gel fibers;

[0176] (3) solvent replacement is performed by using water, and then freeze-drying is performed to obtain hollow aramid aerogel fibers; and the obtained fibers are immersed in a 20wt% perfluoroalkane solution for 3 s, and then taken out at room temperature and normal pressure for 10 min to obtain hollow aramid aerogel fibers with modified hierarchical pore structures.

[0177] By observing the hierarchical pore structure shown in the electron microscope image, Table 1 shows the hierarchical pore structure of the fiber wall of the hollow aramid aerogel fibers with hierarchical pore structures provided in this embodiment and the pore distribution.

[0178] Fig. 11 and Fig. 12 respectively show the nitrogen adsorption-desorption curve and the pore size distribution curve of the hollow aramid aerogel fibers with hierarchical pore structures obtained in this embodiment, to test the specific surface area, from which it can be obtained that the specific surface area of the hollow aramid aerogel fibers with hierarchical pore structures obtained in this embodiment is 315.7717 m 2 / g.

[0179] Obviously, the hollow aramid aerogel fibers with hierarchical pore structures provided in the present application have good adsorption performance, and can be applied to the field of water treatment technology or the field of filtration technology, for example, as a filter core.

[0180] Embodiment 9

[0181] The present embodiment provides a preparation method of hollow aramid aerogel fibers with hierarchical pore structures, and the specific steps include:

[0182] (1) para-aramid and concentrated sulfuric acid (mass ratio of 1.5:8.5) are mixed and used as the spinning solution A, and the concentration of the para-aramid is 15wt%, and water is used as the spinning solution B;

[0183] (2) using a needle head with an inner needle outer diameter of 1 mm and an outer needle inner diameter of 1.3 mm, the spinning solution A and the spinning solution B are simultaneously extruded into a water coagulation bath at an extrusion speed of 300 μL / min, the spinning solution undergoes in-situ dynamic sol-gel transformation in the coagulation bath to obtain hollow aramid gel fibers;

[0184] (3) solvent replacement is performed by using tert-butyl alcohol, and then freeze-drying is performed to obtain hollow aramid aerogel fibers.

[0185] (4) The obtained fiber is immersed in polyethylene glycol for 30 min, and after being taken out, natural placement is performed to obtain the hollow aramid aerogel fiber with modified multi-level pore structure.

[0186] As can be seen from the observation of the aerogel fiber shown in the electron microscope image, the aerogel fiber obtained in this embodiment has a three-dimensional network multi-level pore structure of large pore channels, secondary large pore channels, mesopore channels and micropore channels, and the large pore channels are half-finger-shaped and symmetrically arranged in a radial direction. Table 1 shows the multi-level pore structure of the fiber wall of the aerogel fiber provided in this embodiment and the pore distribution.

[0187] Figure 13 shows the tensile curve of the hollow aramid aerogel fiber with multi-level pore structure obtained in this embodiment. As can be seen from the figure, the tensile strain of the obtained fiber is 14%, and the breaking stress is 0.2 MPa. The modified aerogel phase change fiber provided in this embodiment has a phase change energy storage function and can be used in the field of thermal insulation materials.

[0188] Example 10

[0189] This embodiment provides a preparation method of a hollow aramid aerogel fiber with multi-level pore structure, and the specific steps include:

[0190] (1) The heterocyclic aromatic polyamide fiber, sodium ethoxide, N,N-dimethylformamide and dimethyl sulfoxide (mass ratio of 1:0.1:0.5:8.4) are mixed and used as spinning solution A, and the concentration of the heterocyclic aromatic polyamide fiber is 10 wt%, and 5 wt% agarose / water solution is used as spinning solution B;

[0191] (2) A needle with an inner diameter of 710 μm and an outer diameter of 1 mm is used, and by coaxial wet spinning method, the spinning solution A and the spinning solution B are simultaneously extruded into the ferric chloride / water coagulation bath at an extrusion speed of 500 μL / min, and the spinning solution undergoes in-situ dynamic sol-gel transformation in the coagulation bath to obtain a hollow aramid gel fiber;

[0192] (3) Solvent replacement is performed by ethanol and n-hexane in sequence, and then normal pressure drying is performed to obtain a hollow aramid aerogel fiber.

[0193] (4) The obtained fiber is immersed in fluorocarbon resin for 24 h, and after being taken out, normal pressure drying is performed to obtain a hollow aramid aerogel fiber with modified multi-level pore structure.

[0194] The multi-level pore structure shown in the electron microscope image is observed, and Table 1 shows the multi-level pore structure of the fiber wall of the aerogel fiber provided in this embodiment and the pore distribution.

[0195] Figure 14 shows the water contact angle of the multi-porous structure of the hollow aramid aerogel fiber before and after modification according to the present embodiment. As shown in the figure, the water contact angle increases from 38° to 104.2°, and the hydrophilicity changes to hydrophobicity. The hydrophobic performance of the aerogel fiber provided by the present embodiment can also be applied to the field of water-oil separation technology.

[0196] Referring to Table 1, the pore distribution of the multi-porous structure of the fiber wall of the multi-porous structure of the hollow aramid aerogel fiber provided by the present embodiment 1-10 is shown.

[0197] Table 1 shows the multi-porous structure distribution of the fiber wall provided by the present embodiment

[0198] Table 1 shows the macroporous channel morphology, distribution and pore level of the multi-porous structure of the hollow aramid aerogel fiber provided by the present embodiment 1-10. According to the results of the scanning electron microscope of each embodiment, the multi-porous structure of the fiber wall of the hollow aramid aerogel fiber provided by the present embodiment has needle-like, finger-like or half-finger-like morphology, and is arranged radially. The fiber wall has macroporous channels greater than 10 μm, mesoporous channels of 50 nm-10 μm, mesoporous channels of 2 nm-50 nm and microporous channels less than 2 nm.

[0199] The multi-porous structure of the hollow aramid aerogel fiber provided by the present embodiment has the characteristics of large specific surface area and high porosity. The inner diameter, outer diameter and wall thickness of the fiber, as well as the pore size, pore morphology and pore size distribution on the fiber wall can be controlled, thereby controlling the differential pressure, flux and selectivity of the medium through the tube wall.

[0200] Further, the multi-porous hollow structure prepared by the present embodiment not only meets the requirements of the oxygenation unit of the oxygenator, but also can be used to make the oxygenator of the artificial lung, and can also meet the requirements of waste removal in the process of hemodialysis, and can be used in the dialyzer of the artificial kidney.

[0201] At the same time, it also has good adsorption performance and phase change energy storage function, and can be applied to the fields of water-oil separation, filtration, seawater desalination technology, water treatment technology and thermal insulation materials.

[0202] As can be seen from the technical solutions provided by the present embodiment 1-10, the multi-porous structure of the hollow aramid aerogel fiber provided by the present embodiment has the characteristics of large specific surface area and high porosity, and the inner diameter, outer diameter and wall thickness of the fiber, as well as the pore size, pore morphology and pore size distribution on the fiber wall can be controlled. The preparation process is simple and easy to realize large-scale production. The product can be widely used in the fields of oxygenator, artificial kidney, water-oil separation, filtration, seawater desalination, water treatment, thermal insulation, etc.

[0203] In addition, the applicant also conducted experiments with other raw materials and conditions listed in this specification, referring to Examples 1-10, and similarly obtained hollow aramid aerogel fibers with multi-level porous structures, large specific surface area, and high porosity, in which the fiber inner diameter, outer diameter, wall thickness, pore size, pore morphology, and pore size distribution on the fiber wall can all be controlled.

[0204] It should be noted that the above description is merely a detailed explanation of the preferred embodiments of this application. These embodiments are not intended to limit the scope of this application. Although those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features, any modifications, equivalent substitutions, or improvements made within the spirit and principles of this application should be included within the protection scope of this application. It should be noted that not all operations described in the general description or examples are necessary; some specific operations may not be necessary, and one or more other operations may be performed in addition to those described. Furthermore, the listed order of operations is not necessarily the order in which they are performed.

[0205] Those skilled in the art will understand that various modifications and changes can be made without departing from the scope of this application as defined in the claims. Therefore, the specification and drawings should be considered exemplary rather than limiting, and all such modifications are included within the scope of this application.

[0206] The benefits, other advantages, and solutions to problems have been described above with reference to specific embodiments. However, the benefits, advantages, solutions to problems, and any one or more features that may cause any benefit, advantage, or solution to appear or make it more apparent shall not be construed as key, essential, or fundamental features of any or all claims.

[0207] It should be understood that, for clarity, certain features described herein in the context of individual embodiments may also be provided in combination in a single embodiment. Conversely, for brevity, the various features described in the context of a single embodiment may also be provided individually or in any sub-combination. The use of numerical values ​​within the various ranges specified herein is expressed as approximations, as if both the minimum and maximum values ​​within the range were preceded by the expression "approximately". In this way, slightly higher and lower than the ranges reached can achieve substantially the same results as values ​​within these ranges. Moreover, the disclosure of these ranges is intended as a continuous range including each value between the minimum and maximum average values, including fractional values ​​that may be produced when some components of a value are mixed with components of different values. Furthermore, when wider and narrower ranges are disclosed, it is in the intention of this application that the minimum value from one range matches the maximum value from another range, and vice versa.

Claims

1. A method for preparing a multi-level porous structure hollow aramid aerogel fiber, characterized in that, The method comprises the following steps: uniformly mixing aramid fibers and a first solvent to form a spinning solution A; providing a spinning solution B; simultaneously extruding the spinning solution A and the spinning solution B into a coagulation bath by a coaxial wet spinning method, the spinning solution A being used as a shell layer spinning solution and the spinning solution B being used as a core layer spinning solution, and the spinning solution A undergoing in-situ dynamic sol-gel transformation in the coagulation bath to obtain hollow aramid gel fibers; subsequently, performing solvent replacement-drying treatment to obtain hollow aramid aerogel fibers with a hierarchical porous structure; wherein, in the coaxial wet spinning method, the outer diameter of the inner needle of the coaxial needle is 100 μm to 1.5 mm, the inner diameter of the outer needle of the coaxial needle is 150 μm to 2 mm, and the distance between the outer diameter of the inner needle and the inner diameter of the outer needle is 50 μm to 1000 μm.

2. The production method according to claim 1, characterized by, The aramid fibers in the spinning solution A are any one of para-aramid fibers, meta-aramid fibers, aramid III fibers, aramid copolymer fibers, poly-p-phenyleneterephthalamide fibers, poly-p-phenyleneterephthalamide benzimidazole fibers, and heterocyclic aromatic polyamide fibers, or a combination of two or more thereof. The first solvent comprises any one of N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, methanol, water, acetone, ethanol, and concentrated sulfuric acid, or a combination of two or more thereof. The concentration of the aramid fibers is 0.1 wt% to 30 wt%. The spinning solution B comprises a second solvent with or without added solutes. The solutes are any one of hydroxymethyl cellulose, hydroxyethyl cellulose, sodium alginate, gelatin, polyvinyl alcohol, carbomer, and agarose, or a combination of two or more thereof. The second solvent is any one of water, ethanol, acetone, N-methylpyrrolidone, ethyl acetate, acetonitrile, dimethyl sulfoxide, glycerol, and dimethyl silicone oil, or a combination of two or more thereof. The coagulation bath comprises a third solvent with or without added auxiliary components. The third solvent is any one of water, ethanol, acetone, dimethyl sulfoxide, N-methylpyrrolidone, ethyl acetate, dimethyl silicone oil, N,N-dimethylformamide, glycerol, and tert-butanol, or a combination of two or more thereof. The auxiliary components are any one of calcium chloride, ferric chloride, silver ions, copper ions, hydrochloric acid, sulfuric acid, and acetic acid, or a combination of two or more thereof.

3. The preparation method according to claim 1, characterized in that, The extrusion speed is 50 μL / min to 1000 μL / min.

4. The method of claim 1, wherein, The solvent replacement comprises immersing the hollow aramid gel fibers in a replacement solvent for replacement; the replacement solvent is any one of water, ethanol, tert-butanol, n-hexane, hexafluoroisopropanol, cyclohexane, and acetone, or a combination of two or more thereof. The drying treatment comprises any one of freeze drying, supercritical fluid drying, and atmospheric pressure drying, or a combination of two or more thereof. The freeze drying has a cold trap temperature of -80 ℃ to 15 ℃ and a vacuum degree of less than 0.1 kPa. The supercritical fluid in the supercritical fluid drying comprises any one of supercritical CO2, supercritical methanol, and supercritical ethanol, or a combination of two or more thereof.

5. The method of any one of claims 1-4, wherein, The spinning solution A further comprises an additive. The additive is a first additive, or a combination of the first additive and a second additive. The first additive is any one or a combination of two or more of potassium tert-butoxide, potassium hydroxide, sodium hydride, potassium methoxide, butyl lithium, sodium ethoxide, potassium ethoxide, and sodium hydroxide; The second additive is any one or a combination of two or more of polyethylene glycol, polyacrylonitrile, polyvinyl alcohol, polyvinylpyrrolidone, dibutyl phthalate, and glycerol; The mass ratio of the first additive to aramid fiber is 0.1-1:1; The mass ratio of the second additive to aramid fiber is 0.2-2:

1.

6. A multi-level porous hollow aramid aerogel fiber, prepared by the method of any one of claims 1-5; the multi-level porous hollow aramid aerogel fiber has a hollow structure in the middle part and a three-dimensional network multi-level porous structure in the fiber wall.

7. The hierarchical porous structure's hollow aramid aerogel fiber of claim 6, wherein, The multi-level porous structure includes macro-pore channels, meso-pore channels, and micro-pore channels; the macro-pore channels are perpendicular to the fiber wall and arranged radially.

8. The hierarchical porous structure's hollow aramid aerogel fiber of claim 7, wherein, The macro-pore channels have a finger-shaped through-hole structure, or a needle-shaped or half-finger-shaped half-through-hole structure. The through-hole structure is arranged radially from the inner wall to the outer wall. The half-through-hole structure is located on one side of the fiber wall, or on both the inner side and the outer side of the fiber wall and has a symmetrical structure.

9. The hierarchically porous structure's hollow aramid aerogel fiber of claim 7, wherein, The multi-level porous structure includes meso-pore channels and micro-pore channels.

10. The hierarchical-pore structured hollow aramid aerogel fiber of claim 7, wherein, The multi-level porous hollow aramid aerogel fiber has an outer diameter of 150 μm-2 mm, an inner diameter of 100 μm-1.5 mm, a wall thickness of 50 μm-1000 μm, and a length-diameter ratio of greater than 10.

11. The hierarchically porous structure's hollow aramid aerogel fiber of claim 7, wherein, The hollow aramid aerogel fiber with the multi-level pore structure has a porosity of 60% to 99% and a specific surface area of 10 to 2000 m 2 / g.

12. A modified multi-level porous hollow aramid aerogel fiber, obtained by post-processing of the multi-level porous hollow aramid aerogel fiber prepared by the method of any one of claims 1-5 or the multi-level porous hollow aramid aerogel fiber of any one of claims 6-10. The post-processing includes any one or a combination of two or more of heat treatment, hydrophobization treatment, and filling modification.

13. The modified hierarchical porous structure hollow aramid aerogel fiber of claim 11, wherein, The heat treatment method includes directly placing the multi-level porous hollow aramid aerogel fiber in a tube furnace, treating at a high temperature for 30 min-6 h in a specific atmosphere; the specific atmosphere is any one of nitrogen, argon, and air; the heat treatment temperature is 80-450℃.

14. The modified hierarchical porous structure hollow aramid aerogel fiber of claim 11, wherein, The hydrophobization treatment method includes directly immersing the multi-level porous hollow aramid aerogel fiber in a hydrophobic coating solution for 3 s-1 h, and then taking it out for vacuum drying at room temperature and pressure or at 30-150℃ for 10 min-72 h. The content of the hydrophobic substance in the hydrophobic coating solution is 0.05-20 wt%. The hydrophobic substance includes any one or a combination of two or more of fluorocarbon resin, fluorocarbon modified resin, silicone resin, perfluoroalkane, and polydimethylsiloxane.

15. The modified hierarchical porous structure hollow aramid aerogel fiber of claim 11, wherein, The filling modification method includes immersing the multi-level porous hollow aramid aerogel fiber in a functional liquid material for 30 min-24 h, and then naturally placing it after taking it out. The functional liquid material includes any one or a combination of two or more of polyethylene glycol, liquid paraffin, polyhydric alcohol, dimethyl silicone oil, and perfluoropolyether.

16. Use of the multi-level porous structure hollow aramid aerogel fiber according to any one of claims 6-11 or the modified multi-level porous structure hollow aramid aerogel fiber according to any one of claims 12-15 in oxygenator, artificial kidney, water-oil separation, filtration, seawater desalination, water treatment, thermal insulation fields.

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