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

Abstract

The present invention discloses a hollow aramid aerogel fiber with a multi-level pore structure, and its preparation method and application. The preparation method comprises using a coaxial wet spinning method, using spinning solution A as a shell layer spinning solution and using spinning solution B as a core layer spinning solution, simultaneously extruding the spinning solution A and the spinning solution B into a coagulation bath, causing an in-situ dynamic sol-gel transition, and then performing specific drying to obtain a hollow aramid aerogel fiber with a multi-level pore structure. The hollow aramid aerogel fiber with a multi-level pore structure has a hollow structure in the middle, and the fiber wall has a multi-level pore structure. The hollow aramid aerogel fiber with a multi-level pore structure prepared by the present invention has the characteristics of large specific surface area and high porosity, and the fiber inner diameter, outer diameter and wall thickness, as well as the pore size, pore morphology and pore size distribution on the fiber wall can be controlled. The preparation method is universal, and the preparation process is simple, and it is easy to achieve large-scale production.

Description

Technical Field

[0001] The present invention relates to a hollow air gel fiber, in particular to a hollow aramid aerogel fiber with a multi-level pore structure and a preparation method and application thereof, belonging to the technical field of nanoporous materials and functional fibers. Background Art

[0002] Hollow fibers are a type of fiber material with a tubular cavity running along the fiber axis. This cavity provides a large amount of still air, which not only increases the fiber's bulk and reduces its density, but also improves its warmth retention and moisture permeability. Furthermore, hollow fibers possess high mechanical strength, good oxidation resistance, excellent filtration precision, high flux, and acid and alkali resistance, giving them numerous unique properties and applications. For example, in the textile industry, hollow fibers can be used to make winter clothing, bedding, and padding. In environmental and water resource treatment, hollow fibers can be used for microfiltration, ultrafiltration, dialysis, gas separation, reverse osmosis, and evaporative permeation. In the biomedical field, hollow fibers are used in medical devices such as artificial kidneys and lungs, hemodialysis, drug separation and purification, and in vivo drug activity screening. Clearly, hollow fibers have widespread applications in water treatment, petrochemicals, medicine, biology, food, electronics, energy, air pollution control, aerospace, and military applications.

[0003] Although hollow fibers have demonstrated versatility and high efficiency in different fields, they still face a series of technical problems, such as: (1) low porosity and small specific surface area, resulting in the need to improve membrane flux; (2) pore structure is the key to affecting the performance of hollow fibers, but the current pore structure control method is relatively complex and the effect is still not ideal; (3) currently, the materials used in hollow fibers include polyvinylidene fluoride, polyethersulfone, polypropylene, polyethylene, polytetrafluoroethylene, etc., and new hollow fiber membrane materials need to be developed to suit more complex environments; (4) the production cost is relatively high, and the energy consumption in the production process is high.

[0004] Aerogel is a solid nanomaterial with a three-dimensional network structure. It has ultra-high porosity, large specific surface area, ultra-low density, excellent mechanical properties and wearability. It has important application value in many fields such as textiles, environment, energy conversion and storage, thermal protection, infrared stealth, and electromagnetic shielding. Applying the excellent performance of aerogel and its flexible preparation method to the manufacture of hollow fibers is expected to solve the technical problems of hollow fibers to a certain extent. For example, Chinese invention patent CN118127654A discloses a hollow aerogel fiber and a method for preparing the same at room temperature and pressure. The patent provides a method for preparing a hollow aerogel fiber, comprising preparing a hollow fiber having a porous aerogel structure by synchronously causing non-solvent phase separation inside and outside the fiber at room temperature and pressure, using a coaxial extrusion device, using a non-solvent core liquid for the inner core and a polymer / solvent solution for the outer layer, which are then simultaneously injected into a coagulation bath for coagulation and forming, and drying to obtain the hollow aerogel fiber. However, the material prepared by this method has mostly closed pores, and as can be seen from its coagulation principle and morphology photos, the porosity of the material is relatively low, which is detrimental to the performance of the hollow fiber. For another example, Chinese invention patent CN110607577A discloses a graphene aerogel hollow fiber, a preparation method and application thereof, but graphene aerogel materials are generally brittle, and the pore structure, morphology and distribution cannot be controlled, making it difficult to simultaneously solve the problems of high selectivity and high flux, and having a narrow scope of application. Furthermore, Chinese invention patent CN117512809A discloses a core-shell aramid / cellulose aerogel fiber and its preparation method. Aramid fibers are dissolved in an aprotic solvent in an alkaline environment to produce a shell spinning solution. Nanocellulose powder is placed in deionized water and ultrasonically dispersed to produce a core spinning solution. After wet spinning, coagulation, and winding, the solution is replaced in solvents with varying concentration gradients and dried to produce the core-shell aramid / cellulose aerogel fiber. The aerogel fiber prepared by this invention has a double-layer structure. The core fiber has abundant pores, ultra-low density, and ultra-high specific surface area, while the shell fiber has a dense surface, high temperature resistance, and high strength. However, this method produces core-shell fibers, and the method has a limited range of control over the fiber pores, making it more difficult.

[0005] Based on this, the present invention develops a new method for preparing hollow aramid aerogel fibers with a 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 regulated by regulating the spinning solution and spinning process parameters to meet the needs of high selectivity and high throughput in practical applications. Summary of the Invention

[0006] The present invention aims to provide a hollow aramid aerogel fiber with a multi-level pore structure, as well as its preparation method and application, to overcome the shortcomings of the prior art. By regulating the fiber's inner diameter, outer diameter, and wall thickness, as well as the pore size, pore morphology, and pore size distribution, the pressure differential, flux, and selectivity of the medium passing through the tube wall can be controlled. This yields a hollow aramid aerogel fiber that meets the requirements, improving and expanding the performance and application range of the aerogel fibers previously used.

[0007] To achieve the aforementioned object of the invention, the present invention provides a method for preparing a hollow aramid aerogel fiber with a multi-level pore structure, which comprises:

[0008] At least aramid fiber and a first solvent are uniformly mixed and used as a spinning solution A;

[0009] Providing spinning solution B;

[0010] A coaxial spinning method is adopted. Spinning solution A and spinning solution B are injected from two inlets respectively and "mixed" at the needle. In the presence of a coagulation bath, a sol-gel transition occurs, and spinning solution A is coated on the surface of spinning solution B. Subsequently, the hollow aramid aerogel fiber with the multi-level pore structure is obtained through solvent replacement, drying and post-treatment.

[0011] In the present invention, the coagulation bath is a static coagulation bath, but the spinning solution is extruded into the static coagulation bath in a dynamic form, and sol-gel transformation occurs while being extruded, that is, in-situ dynamic sol-gel transformation, to obtain aramid gel fibers with a hollow structure; finally, after post-treatment, hollow aramid aerogel fibers with a multi-level pore structure are formed.

[0012] In particular, the hollow aramid aerogel fiber obtained by the above technical solution has a multi-level pore structure; and by adjusting the raw materials and process parameters, aerogel fibers with multiple pore levels, different pore distributions and different morphologies can be obtained, while solving the problems of high selectivity and high throughput of aerogel materials.

[0013] Furthermore, the aramid fiber is any one of para-aramid, meta-aramid, aramid III, aramid copolymer fiber, poly(p-phenylene terephthalamide), poly(p-aramid benzimidazole) fiber, and heterocyclic aromatic polyamide fiber, or a combination of two or more thereof.

[0014] Furthermore, the first solvent includes any one or a combination of two or more of nitrogen-methyl pyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, methanol, water, acetone, ethanol, and concentrated sulfuric acid.

[0015] Furthermore, the concentration of the aerogel precursor is 0.1 to 30 wt%.

[0016] Furthermore, the spinning solution B includes a second solvent with or without added solute.

[0017] Furthermore, 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.

[0018] Furthermore, the second solvent includes any one or a combination of two or more of water, ethanol, acetone, nitrogen-methyl pyrrolidone, ethyl acetate, acetonitrile, dimethyl sulfoxide, glycerol, dimethyl silicone oil, and N,N-dimethylformamide.

[0019] Furthermore, the coagulation bath includes a third solvent with or without added auxiliary components.

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

[0021] Furthermore, the auxiliary components include any one or a combination of two or more of calcium chloride, ferric chloride, silver ions, copper ions, hydrochloric acid, sulfuric acid, and acetic acid.

[0022] Furthermore, in the coaxial needle, the outer diameter of the inner needle is 100 μm to 1.5 mm, the inner diameter of the outer needle is 150 μm to 2 mm, the distance between the outer diameter of the inner needle and the inner diameter of the outer needle is 50 μm to 1000 μm, and the extrusion speed is 50 to 1000 μL / min.

[0023] Furthermore, the replacement solvent is one or a combination of two or more of water, ethanol, tert-butanol, n-hexane, hexafluoroisopropanol, cyclohexane, and acetone.

[0024] Furthermore, the drying process includes any one of freeze drying, supercritical fluid drying, and normal pressure drying, or a combination of two or more thereof.

[0025] As a preferred embodiment, the spinning solution A further includes additives.

[0026] Preferably, the additive is the first additive, or a combination of the first additive and the second additive;

[0027] Preferably, 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;

[0028] Preferably, the second additive is any one or a combination of two or more of polyethylene glycol, polyacrylonitrile, polyvinyl alcohol, polyvinyl pyrrolidone, dibutyl phthalate, and glycerol;

[0029] Preferably, the mass ratio of the first additive to the aramid fiber is 0.1 to 1:1;

[0030] Preferably, the mass ratio of the second additive to the aramid fiber is 0.2 to 2:1;

[0031] As one of the objects of the invention, the present invention further provides a hollow aramid aerogel fiber with a modified multi-level pore structure, which is prepared by post-processing the aforementioned hollow aramid aerogel fiber with a multi-level pore structure.

[0032] Furthermore, the post-treatment includes any one or a combination of two or more of heat treatment, hydrophobic treatment, and filling modification.

[0033] Preferably, the heat treatment method includes placing the hollow aramid aerogel fiber with a multi-level pore structure directly in a tubular furnace, and subjecting it to high-temperature treatment for 30 minutes to 6 hours under a specific atmosphere; the specific atmosphere is any one of nitrogen, argon, and air; and the heat treatment temperature is 80 to 450°C.

[0034] Preferably, the hydrophobic treatment method includes directly immersing the hollow aramid aerogel fiber with a multi-level pore structure in a hydrophobic coating solution for 3 seconds to 1 hour, then taking it out and vacuum drying it at room temperature and pressure or 30 to 150°C for 10 minutes to 72 hours; the content of hydrophobic substance in the hydrophobic coating solution is 0.05 to 20 wt%.

[0035] 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.

[0036] Preferably, the filling and modification method comprises immersing the hollow aramid aerogel fiber with a multi-level pore structure in a functional liquid material for 30 minutes to 24 hours, taking it out and placing it naturally.

[0037] Preferably, the functional liquid includes any one of polyethylene glycol, liquid paraffin, polyol, dimethyl silicone oil, and perfluoropolyether, or a combination of two or more thereof.

[0038] As one of the objects of the invention, the present invention also provides a hollow aramid aerogel fiber with a multi-level pore structure, the middle part of the fiber is a hollow structure, the fiber wall is a multi-level pore structure, the outer diameter of the aerogel fiber in the multi-level pore is 150μm~2mm, the inner diameter is 100μm~1.5mm, the wall thickness is 50μm~1000μm, and the aspect ratio is greater than 10.

[0039] As a preferred embodiment, the multi-level pore structure includes sub-macroporous channels, mesoporous channels and microporous channels.

[0040] As a preferred embodiment, the multi-level pore structure includes macroporous channels, sub-macroporous channels, mesoporous channels and microporous channels.

[0041] Preferably, the multi-level pore structure includes macropore channels larger than 10 μm, sub-macropore channels of 50 nm to 10 μm, mesopore channels of 2 nm to 50 nm, and micropore channels smaller than 2 nm.

[0042] Furthermore, the macroporous channels are arranged radially perpendicular to the inner and outer walls of the fiber.

[0043] More preferably, the macroporous channel is in the shape of a finger-shaped through-hole structure, or a needle-shaped or semi-finger-shaped semi-through-hole structure.

[0044] Preferably, the through hole structure is radially arranged from the inner wall to the outer wall.

[0045] Preferably, the semi-through hole structure is located on one side of the fiber wall, or located on the inner side and the outer side of the fiber wall, and has a symmetrical structure.

[0046] In some specific embodiments, the porosity of the multi-level pore hollow aramid aerogel fiber is 60% to 99%, and the specific surface area is 10 to 2000 m 2 / g.

[0047] The type of raw materials, addition ratio, process parameters, etc. in the preparation process can be regulated according to actual needs to prepare radially arranged macroporous channels. The macroporous channels can be radially arranged finger-like through-hole structures, or needle-like or semi-finger-like semi-through-hole structures radially arranged on one side of the fiber wall, or semi-finger-like semi-through-hole structures symmetrically radially arranged on the inside and outside of the fiber wall, etc., so as to obtain aerogel fiber materials with different fluxes and different multi-level pore structures according to actual needs.

[0048] The aramid aerogel fibers prepared using the above method have a multi-level porous, hollow structure, and the fiber inner diameter, outer diameter, and wall thickness, as well as the pore size, pore morphology, and pore size distribution on the fiber wall, can all be controlled. Furthermore, by manipulating the preparation process parameters, the pressure difference across the fiber tube wall, flux, and selectivity can be adjusted to produce hollow aramid aerogel fibers with a multi-level porous structure that meet the requirements of various fields. Specifically, the aforementioned hollow aramid aerogel fibers with a multi-level porous structure or modified hollow aramid aerogel fibers with a multi-level porous structure can be used in oxygenators, artificial kidneys, water-oil separation, filtration, seawater desalination, water treatment, thermal insulation, and other fields.

[0049] Based on the application requirements of different fields, the method provided by the present invention is highly universal, and the preparation process is simple and easy to achieve large-scale production.

[0050] Compared with the prior art, the advantages of the present invention include:

[0051] (1) The present invention adopts a coaxial wet spinning method. By adjusting the raw materials and process parameters, hollow aramid aerogel fibers with multiple pore levels, different pore distributions and different pore morphologies can be obtained, thereby solving the problem of high selectivity and high throughput of aerogel materials.

[0052] (2) The method for preparing hollow aramid aerogel fibers with a multi-level pore structure provided by the present invention does not require complex synthesis technology, has a simple process, low energy consumption, low production cost, and is suitable for large-scale production and application.

[0053] (3) The hollow aramid aerogel fiber with a multi-level pore structure provided by the present invention has a hollow structure in the middle and a multi-level pore structure in the fiber wall, wherein the multi-level pore structure includes macroporous channels, sub-macroporous channels, mesoporous channels and microporous channels; the obtained hollow aramid aerogel fiber with a multi-level pore structure has a large specific surface area and a high porosity, and the pore size, pore morphology and pore size distribution on the fiber wall can be adjusted as needed. In particular, its porous structure has extremely strong designability.

[0054] (4) The hollow aramid aerogel fiber with a multi-level pore structure provided by the present invention can be heat-treated, hydrophobized, and filled according to the use environment, and can be used in oxygenators, artificial kidneys, water-oil separation, filtration, seawater desalination, water treatment, thermal insulation and other fields, greatly expanding and improving the application range and performance of aerogels and hollow fibers. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0056] Figure 1 This is an optical photograph of the hollow aramid aerogel fiber with a multi-level pore structure prepared by the present invention.

[0057] Figure 2 A scanning electron microscope image of a hollow aramid aerogel fiber with a multi-level pore structure in a typical embodiment of the present invention is shown.

[0058] Figure 3A scanning electron microscope image of a hollow aramid aerogel fiber with a multi-level pore structure in a typical embodiment of the present invention is shown.

[0059] Figure 4 A scanning electron microscope image of a hollow aramid aerogel fiber with a multi-level pore structure in a typical embodiment of the present invention is shown.

[0060] Figure 5 A scanning electron microscope image of a hollow aramid aerogel fiber with a multi-level pore structure in a typical embodiment of the present invention is shown.

[0061] Figure 6 A scanning electron microscope image of a hollow aramid aerogel fiber with a multi-level pore structure in a typical embodiment of the present invention is shown.

[0062] Figure 7 A scanning electron microscope image of a hollow aramid aerogel fiber with a multi-level pore structure in a typical embodiment of the present invention is shown.

[0063] Figure 8 A locally enlarged scanning electron microscope image of a hollow aramid aerogel fiber with a multi-level pore structure in a typical embodiment of the present invention is shown.

[0064] Figure 9 The figure shows a specific surface area test curve of a hollow aramid aerogel fiber with a multi-level pore structure in a typical embodiment of the present invention.

[0065] Figure 10 The figure shows the tensile curve of the hollow aramid aerogel fiber with a multi-level pore structure in a typical embodiment of the present invention.

[0066] Figure 11 The water contact angles of the hollow aramid aerogel fibers with hierarchical pore structures before and after modification in a typical embodiment of the present invention are shown. DETAILED DESCRIPTION

[0067] In view of the deficiencies in the prior art, the present invention develops a hollow aramid aerogel fiber with a multi-level pore structure and its preparation method and application, in order to expand the application range of aerogels and hollow fibers.

[0068] See Figure 1 As shown, the middle part of the hollow aramid aerogel fiber with a multi-level pore structure provided by the present invention is a hollow structure, and the fiber wall has a multi-level pore structure, wherein the multi-level pores include macropore channels, sub-macropore channels, mesopore channels and micropore channels.

[0069] The preparation method mainly comprises the following steps: uniformly mixing at least aramid fiber and solvent and using the mixture as spinning solution A; providing spinning solution B; simultaneously squeezing spinning solution A and spinning solution B into a coagulation bath through a coaxial wet spinning method, wherein the spinning solution undergoes an in-situ dynamic sol-gel transformation in the coagulation bath to obtain hollow aramid gel fiber; and subsequently obtaining a hollow aramid aerogel fiber with a multi-level pore structure through solvent replacement, drying and post-treatment.

[0070] The technical solution, its implementation process and principles are further explained below.

[0071] One aspect of an embodiment of the present invention provides a method for preparing a hollow aramid aerogel fiber with a multi-level pore structure, comprising:

[0072] At least aramid fiber and a first solvent are uniformly mixed and used as a spinning solution A;

[0073] Providing spinning solution B;

[0074] Through the coaxial wet spinning method, spinning solution A and spinning solution B are squeezed into the coagulation bath at the same time, and the spinning solution undergoes dynamic sol-gel transformation in situ in the coagulation bath to obtain hollow aramid gel fiber;

[0075] Subsequently, hollow aramid aerogel fibers with a hierarchical pore structure were obtained through solvent replacement, drying and post-treatment.

[0076] In some preferred embodiments, the aramid fiber includes 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 is not limited thereto.

[0077] Furthermore, the first solvent includes any one or a combination of two or more of nitrogen-methyl pyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, methanol, water, acetone, ethanol, and concentrated sulfuric acid, but is not limited thereto.

[0078] Furthermore, in the spinning solution A, the concentration of the aramid fiber is 0.1 to 30 wt%.

[0079] The spinning solution A further includes additives;

[0080] Further, the additive is a first additive, or a combination of the first additive and a second additive;

[0081] Furthermore, 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;

[0082] Furthermore, the second additive is any one or a combination of two or more of polyethylene glycol, polyacrylonitrile, polyvinyl alcohol, polyvinyl pyrrolidone, dibutyl phthalate, and glycerol;

[0083] Furthermore, the mass ratio of the first additive to the aramid fiber is 0.1 to 1:1;

[0084] Furthermore, the mass ratio of the second additive to the aramid fiber is 0.2 to 2:1;

[0085] In some preferred embodiments, the spinning solution B includes a second solvent with or without added solute;

[0086] Furthermore, 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, but is not limited thereto.

[0087] Furthermore, the second solvent includes any one or a combination of two or more of water, ethanol, acetone, nitrogen-methyl pyrrolidone, ethyl acetate, acetonitrile, dimethyl sulfoxide, glycerol, dimethyl silicone oil, and N,N-dimethylformamide, but is not limited thereto.

[0088] In some preferred embodiments, the coagulation bath includes a third solvent with or without added auxiliary ingredients;

[0089] Furthermore, the third solvent includes any one or a combination of two or more of water, ethanol, acetone, dimethyl sulfoxide, nitrogen methyl pyrrolidone, ethyl acetate, dimethyl silicone oil, N,N-dimethylformamide, glycerol, and tert-butanol, but is not limited thereto.

[0090] Furthermore, the auxiliary components include any one or a combination of two or more of calcium chloride, ferric chloride, silver ions, copper ions, hydrochloric acid, sulfuric acid, and acetic acid, but are not limited thereto.

[0091] In some preferred embodiments, the inner needle outer diameter of the coaxial needle suitable for the coaxial wet spinning method is 100 μm to 1.5 mm, the outer needle inner diameter is 150 μm to 2 mm, and the distance between the inner needle outer diameter and the outer needle inner diameter is 50 μm to 1000 μm.

[0092] Furthermore, the extrusion speed is 50 to 1000 μL / min.

[0093] In some preferred embodiments, the replacement solvent is one or a combination of two or more of water, ethanol, tert-butanol, n-hexane, hexafluoroisopropanol, cyclohexane, and acetone, but is not limited thereto.

[0094] In some preferred embodiments, the drying process includes any one of freeze drying, supercritical fluid drying, and atmospheric pressure drying, or a combination of two or more thereof, but is not limited thereto.

[0095] Furthermore, the temperature of the cold trap for freeze drying is -80 to 15° C., and the vacuum degree is less than 0.1 kPa.

[0096] Furthermore, the supercritical fluid in the supercritical fluid drying includes any one of supercritical CO2, supercritical methanol and supercritical ethanol.

[0097] Another aspect of the embodiments of the present invention further provides post-processing of the hollow aramid aerogel fiber with the multi-level pore structure.

[0098] Preferably, the post-treatment includes any one of heat treatment, hydrophobization treatment, filling modification, etc.

[0099] Specifically, the post-processing method can be any one of the following methods:

[0100] (1) directly placing the hollow aramid aerogel fiber with a multi-level pore structure in a tubular furnace and subjecting it to high-temperature treatment for 30 minutes to 6 hours under a specific atmosphere; the atmosphere is one of nitrogen, argon, and air; and the heat treatment temperature is 80 to 450° C.;

[0101] (2) The hollow aramid aerogel fiber with a multi-level pore structure is directly immersed in a hydrophobic coating solution for 3 seconds to 1 hour, and then taken out and vacuum dried at room temperature and pressure or 30 to 150°C for 10 minutes to 72 hours; 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.

[0102] (3) Immersing the hollow aramid aerogel fiber with a multi-level pore structure in a functional liquid material for 30 minutes to 24 hours, taking it out and placing it naturally; 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.

[0103] Another aspect of an embodiment of the present invention further provides a hollow aramid aerogel fiber with a multi-level pore structure, wherein the middle portion of the hollow aramid aerogel fiber with a multi-level pore structure is a hollow structure, and the fiber wall has a multi-level pore structure; the multi-level pore structure includes macroporous channels, sub-macroporous channels, mesoporous channels and microporous channels; the macroporous channels are arranged perpendicular to the inner and outer walls of the fiber.

[0104] In some preferred embodiments, the outer diameter of the hollow aramid aerogel fiber with a multi-level pore structure 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 aspect ratio is greater than 10, but not limited thereto.

[0105] Furthermore, the porosity of the hollow aramid aerogel fiber with a multi-level pore structure is 60% to 99%, and the specific surface area is 10 to 2000 m 2 / g, but not limited to this.

[0106] Another aspect of the embodiments of the present invention further provides applications of the aforementioned hollow aramid aerogel fiber with a multi-level pore structure or the hollow aramid aerogel fiber with a modified multi-level pore structure in the fields of oxygenators, artificial kidneys, water-oil separation, filtration, seawater desalination, water treatment, thermal insulation, etc.

[0107] Specifically, in the application, at least part of the components adopt the aforementioned hollow aramid aerogel fiber with a multi-level pore structure.

[0108] The coaxial wet spinning method provided by the present invention can obtain hollow aramid aerogel fibers with multiple pore levels, different pore 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.

[0109] The method for preparing hollow aramid aerogel fibers with a multi-level pore structure provided by the present invention does not require complex synthesis technology, has a simple process, low energy consumption, low production cost, and is suitable for large-scale production and application;

[0110] The hollow aramid aerogel fibers provided by the present invention have a multi-level pore structure with a hollow center and a multi-level pore structure in the fiber wall. The multi-level pore structure includes macroporous channels, sub-macroporous channels, mesoporous channels, and microporous channels. They have a large specific surface area and high porosity. The pore size, morphology, and pore size distribution of the fiber wall can be adjusted as needed, making the structure highly designable.

[0111] The hollow aramid aerogel fiber with a multi-level pore structure provided by the present invention can be heat-treated, hydrophobized, and filled and modified according to the use environment, and can be used in oxygenators, artificial kidneys, water-oil separation, filtration, seawater desalination, water treatment, thermal insulation and other fields, greatly expanding and improving the application range and performance of aerogels and hollow fiber membranes.

[0112] In summary, the method for preparing a hollow aramid aerogel fiber with a hierarchical pore structure provided by the present invention comprises uniformly mixing at least aramid fibers and a solvent to form a spinning solution A; providing a spinning solution B; and simultaneously extruding the spinning solution A and the spinning solution B into a coagulation bath via a coaxial wet spinning method. The spinning solution undergoes an in-situ dynamic sol-gel transformation in the coagulation bath to obtain a hollow aramid gel fiber. Subsequently, the hollow aramid aerogel fiber with a hierarchical pore structure is obtained by solvent replacement, drying, and post-processing. The hollow aramid aerogel fiber with a hierarchical pore structure of the present invention can be used in oxygenators, artificial kidneys, water-oil separation, filtration, seawater desalination, water treatment, thermal insulation, and other fields.

[0113] The technical solution of the present invention is further described in detail below through several embodiments and in conjunction with the accompanying drawings. However, the selected embodiments are only used to illustrate the present invention and do not limit the scope of the present invention. Those skilled in the art may adjust according to actual conditions.

[0114] Example 1

[0115] This embodiment provides a method for preparing a hollow aramid aerogel fiber with a multi-level pore structure, and the specific steps include:

[0116] (1) para-aramid, potassium tert-butoxide, methanol, and dimethyl sulfoxide in a mass ratio of 0.6:0.3:0.6:8.5 were mixed as spinning solution A, and the concentration of para-aramid was 6 wt%; a 1 wt% sodium alginate / water solution was used as spinning solution B;

[0117] (2) Using a coaxial needle with an inner needle outer diameter of 710 μm and an outer needle inner diameter of 1.5 mm, spinning solution A and spinning solution B were mixed and extruded into an ethanol / water coagulation bath at an extrusion speed of 700 μL / min. The spinning solution underwent in-situ dynamic sol-gel transformation in the coagulation bath to obtain hollow aramid gel fibers;

[0118] (3) using water as a replacement solvent, immersing the aramid gel fiber in the replacement solvent for solvent replacement, and then freeze-drying, wherein the cold trap temperature of the freeze-drying is -80 to 15°C and the vacuum degree is less than 0.1 kPa; finally, a hollow aramid aerogel fiber with a multi-level pore structure is obtained;

[0119] (4) The obtained fiber was heat treated at 100°C for 6 h in a nitrogen atmosphere to obtain a hollow aramid aerogel fiber with a modified multi-level pore structure.

[0120] See Figure 1 , which is a physical photo of the hollow aramid aerogel fiber with a multi-level pore structure prepared in this example.

[0121] See Figure 2, which is a scanning electron microscope image of the hollow aramid aerogel fiber with a multi-level pore structure prepared in this embodiment. It can be seen from the figure that the obtained fiber has a hollow structure and the fiber wall presents a three-dimensional network-like porous structure.

[0122] Example 2

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

[0124] (1) A spinning solution A was prepared by mixing aramid copolymer fiber, potassium methoxide, polyvinyl pyrrolidone, and dimethyl sulfoxide (in a mass ratio of 0.8:0.8:1.6:6.8), wherein the concentration of the aramid copolymer fiber was 8 wt %. A spinning solution B was prepared by mixing a carbomer / glycerol mixture (with a carbomer concentration of 0.5 wt %).

[0125] (2) Using a needle with an inner needle outer diameter of 1.2 mm and an outer needle inner diameter of 2 mm, spinning solution A and spinning solution B were simultaneously extruded into a dilute hydrochloric acid coagulation bath at an extrusion speed of 800 μL / min by a coaxial wet spinning method. The spinning solutions underwent in-situ dynamic sol-gel transformation in the coagulation bath to obtain hollow aramid gel fibers;

[0126] (3) using acetone as the replacement solvent to perform solvent replacement, followed by supercritical carbon dioxide drying to obtain a hollow aramid aerogel fiber with a hierarchical pore structure;

[0127] (4) The obtained fiber was heat treated at 80°C for 3 h in an argon atmosphere to obtain a hollow aramid aerogel fiber with a modified multi-level pore structure.

[0128] Figure 3 A scanning electron microscope image of the hollow aramid aerogel fiber with a multi-level pore structure obtained in this embodiment is shown. As can be seen from the image, the middle part of the fiber is a hollow structure, and the fiber wall has a three-dimensional network-like multi-level pore structure, in which the macropore channels are radially arranged in a needle-like form.

[0129] Example 3

[0130] This embodiment provides a method for preparing a hollow aramid aerogel fiber with a multi-level pore structure, and the specific steps include:

[0131] (1) poly(p-phenylene terephthalamide), sodium hydride, polyvinyl alcohol, and dimethyl sulfoxide (mass ratio 1:1:0.2:7.8) were mixed and used as spinning solution A, the concentration of poly(p-phenylene terephthalamide) was 10 wt %, and acetone was used as spinning solution B;

[0132] (2) Using a needle with an inner needle outer diameter of 510 μm and an outer needle inner diameter of 1 mm, spinning solution A and spinning solution B were simultaneously extruded into an acetone / dimethyl sulfoxide / water coagulation bath at an extrusion speed of 500 μL / min by a coaxial wet spinning method. The spinning solutions underwent in-situ dynamic sol-gel transformation in the coagulation bath to obtain hollow aramid gel fibers.

[0133] (3) The solvent was replaced by water and anhydrous ethanol, and then dried with supercritical carbon dioxide to obtain hollow aramid aerogel fibers with a multi-level pore structure.

[0134] (4) The fiber obtained in step (3) is heat-treated at 100° C. for 6 h in an air atmosphere to obtain a hollow aramid aerogel fiber with a modified multi-level pore structure.

[0135] Figure 4 A scanning electron microscope magnified image of the fiber wall of the hollow aramid aerogel fiber with a multi-level pore structure obtained in this embodiment is shown. As can be seen from the image, the fiber wall has a multi-level pore structure, including macroporous channels, sub-macroporous channels, mesoporous channels and microporous channels.

[0136] Example 4

[0137] This embodiment provides a method for preparing a hollow aramid aerogel fiber with a multi-level pore structure, and the specific steps include:

[0138] (1) Poly(para-aramid benzimidazole) fiber, sodium hydroxide, polyethylene glycol, N,N-dimethylformamide, and dimethyl sulfoxide (mass ratio of 0.1:0.1:0.2:0.1:99.5) were mixed and used as spinning solution A. The concentration of poly(para-aramid benzimidazole) fiber was 0.1 wt%, and N,N-dimethylformamide was used as spinning solution B.

[0139] (2) Using a needle with an inner needle outer diameter of 300 μm and an outer needle inner diameter of 710 μm, spinning solution A and spinning solution B were simultaneously extruded into a water coagulation bath at an extrusion speed of 350 μL / min through a coaxial wet spinning method. The spinning solutions underwent in-situ dynamic sol-gel transformation in the coagulation bath to obtain hollow aramid gel fibers.

[0140] (3) Solvent replacement was performed with water and tert-butyl alcohol, followed by freeze drying to obtain air gel fibers.

[0141] (4) The obtained fiber was heat treated at 300 °C for 30 min in an argon atmosphere to obtain a hollow aramid aerogel fiber with a modified multi-level pore structure, which can be used in the field of water-oil separation.

[0142] Figure 5 The scanning electron microscope image of the hollow aramid aerogel fiber with a multi-level pore structure obtained in this embodiment is shown. As can be seen from the image, the macroporous channels are radially arranged in the fiber wall in a finger-like form.

[0143] Example 5

[0144] This embodiment provides a method for preparing a hollow aramid aerogel fiber with a multi-level pore structure, and the specific steps include:

[0145] (1) poly(para-aramid benzimidazole) fiber, potassium ethoxide, polyvinyl pyrrolidone, and dimethyl sulfoxide (mass ratio 0.4:0.4:0.6:8.6) were mixed and used as spinning solution A, the concentration of poly(para-aramid benzimidazole) fiber was 4 wt %, and a 5 wt % hydroxymethyl cellulose / water solution was used as spinning solution B;

[0146] (2) Using a needle with an inner needle outer diameter of 300 μm and an outer needle inner diameter of 710 μm, spinning solution A and spinning solution B were simultaneously extruded into a water coagulation bath at an extrusion speed of 500 μL / min by a coaxial wet spinning method. The spinning solutions underwent in-situ dynamic sol-gel transformation in the coagulation bath to obtain hollow aramid gel fibers;

[0147] (3) The hollow aramid aerogel fibers with a hierarchical pore structure were obtained by solvent replacement with water and acetone and subsequent drying with supercritical carbon dioxide.

[0148] (4) The obtained fiber was then heat treated at 450 °C for 30 min in an argon atmosphere to obtain a hollow aramid aerogel fiber with a modified multi-level pore structure.

[0149] Figure 6 The scanning electron microscope image of the hollow aramid aerogel fiber with a multi-level pore structure obtained in this embodiment is shown. As can be seen from the image, the macroporous channels are unilaterally and radially arranged in the fiber wall in a semi-finger-like form.

[0150] Example 6

[0151] This embodiment provides a method for preparing a hollow aramid aerogel fiber with a multi-level pore structure, and the specific steps include:

[0152] (1) Poly(p-phenylene terephthalamide), sodium hydride, polyethylene glycol, ethanol, and dimethyl sulfoxide (mass ratio 0.4:0.4:0.8:0.2:8.2) were mixed to form spinning solution A, the concentration of poly(p-phenylene terephthalamide) was 4 wt %, and water was used as spinning solution B;

[0153] (2) Using a needle with an inner needle outer diameter of 250 μm and an outer needle inner diameter of 510 μm, spinning solution A and spinning solution B were simultaneously extruded into an acetonitrile / water coagulation bath at an extrusion speed of 1000 μL / min by a coaxial wet spinning method. The spinning solutions underwent in-situ dynamic sol-gel transformation in the coagulation bath to obtain hollow aramid gel fibers;

[0154] (3) Solvent replacement was performed with ethanol, followed by supercritical carbon dioxide drying to obtain hollow aramid aerogel fibers with a multi-level pore structure.

[0155] (4) The obtained fiber was then heat treated at 80 °C for 1 h under an argon atmosphere to obtain a hollow aramid aerogel fiber with a modified multi-level pore structure, which can be used as an oxygenator.

[0156] Figure 7 The scanning electron microscope image of the hollow aramid aerogel fiber with a multi-level pore structure obtained in this embodiment is shown. As can be seen from the image, the macroporous channels are radially arranged in the fiber wall in a symmetrical semi-finger shape, having a multi-level pore structure.

[0157] Example 7

[0158] This embodiment provides a method for preparing a hollow aramid aerogel fiber with a multi-level pore structure, and the specific steps include:

[0159] (1) para-aramid, sodium ethoxide, ethanol, and dimethyl sulfoxide (mass ratio: 0.2:0.2:0.2:9.4) were mixed as spinning solution A, the concentration of para-aramid was 2 wt%, and ethyl acetate was used as spinning solution B;

[0160] (2) Using a needle with an inner needle outer diameter of 100 μm and an outer needle inner diameter of 150 μm, spinning solution A and spinning solution B were simultaneously extruded into a calcium chloride / water coagulation bath at an extrusion speed of 50 μL / min by a coaxial wet spinning method. The spinning solutions underwent in-situ dynamic sol-gel transformation in the coagulation bath to obtain hollow aramid gel fibers;

[0161] (3) Solvent replacement was performed with water and tert-butyl alcohol in sequence, followed by freeze drying to obtain air gel fibers.

[0162] (4) The obtained fiber was heat treated at 100°C for 3 h in an argon atmosphere to obtain a hollow aramid aerogel fiber with a modified multi-level pore structure.

[0163] Figure 8 A scanning electron microscope magnified image of the hollow aramid aerogel fiber with a multi-level pore structure obtained in this embodiment is shown. The image shows that the fiber wall has a multi-level pore structure of sub-macroporous channels, mesoporous channels and microporous channels.

[0164] Example 8

[0165] This embodiment provides a method for preparing a hollow aramid aerogel fiber with a multi-level pore structure, and the specific steps include:

[0166] (1) poly(para-aramid benzimidazole) fiber and concentrated sulfuric acid (mass ratio: 3:7) were mixed as spinning solution A, the concentration of poly(para-aramid benzimidazole) fiber was 30 wt%; water was used as spinning solution B;

[0167] (2) Using a needle with an inner needle outer diameter of 300 μm and an outer needle inner diameter of 550 μm, spinning solution A and spinning solution B were simultaneously extruded into an anhydrous calcium chloride / water coagulation bath at an extrusion speed of 500 μL / min by a coaxial wet spinning method. The spinning solutions underwent in-situ dynamic sol-gel transformation in the coagulation bath to obtain hollow aramid gel fibers;

[0168] (3) Solvent replacement was performed with water, followed by freeze drying to obtain hollow aramid aerogel fibers; the obtained fibers were immersed in a 20 wt% perfluoroalkane solution for 3 seconds, and then taken out and incubated at room temperature and pressure for 10 minutes to obtain hollow aramid aerogel fibers with a modified multi-level pore structure.

[0169] By observing the multi-level pore structure shown in the electron microscope image, Table 1 shows the multi-level pore structure and pore distribution of the fiber wall of the hollow aramid aerogel fiber with a multi-level pore structure provided in this embodiment.

[0170] Figure 9 The specific surface area test curve of the hollow aramid aerogel fiber with a multi-level pore structure obtained in this embodiment is shown. It can be seen from the figure that the specific surface area of ​​the hollow aramid aerogel fiber with a multi-level pore structure obtained is 315.7717m 2 / g.

[0171] Obviously, the hollow aramid aerogel fiber with a multi-level pore structure provided by the present invention has good adsorption performance and can be used as an adsorption material in the field of water treatment technology or filtration technology, such as a filter element.

[0172] Example 9

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

[0174] (1) para-aramid and concentrated sulfuric acid (mass ratio of 1.5:8.5) were mixed as spinning solution A, the concentration of para-aramid was 15 wt%, and water was used as spinning solution B;

[0175] (2) Using a needle with an inner needle outer diameter of 1 mm and an outer needle inner diameter of 1.3 mm, spinning solution A and spinning solution B were simultaneously extruded into a water coagulation bath at an extrusion speed of 300 μL / min by a coaxial wet spinning method. The spinning solutions underwent in-situ dynamic sol-gel transformation in the coagulation bath to obtain hollow aramid gel fibers;

[0176] (3) Solvent replacement was performed with tert-butyl alcohol, followed by freeze drying to obtain hollow aramid aerogel fibers.

[0177] (4) The obtained fiber was immersed in polyethylene glycol for 30 minutes, taken out and placed naturally to obtain a hollow aramid aerogel fiber with a modified multi-level pore structure.

[0178] By observing the aerogel fibers shown in the electron microscope image, it can be seen that the aerogel fibers obtained in this embodiment have a three-dimensional network of multi-level pore structure of macropore channels, sub-macropore channels, mesopore channels, and micropore channels, and the macropore channels are semi-finger-shaped and symmetrically arranged radially. Table 1 shows the multi-level pore structure and pore distribution of the fiber wall of the aerogel fiber provided in this embodiment.

[0179] Figure 10 The tensile curve of the hollow aramid aerogel fiber with a multi-level pore structure obtained in this example shows a tensile strain of 14% and a breaking stress of 0.2 MPa. The modified aerogel-based phase change fiber provided in this example has phase change energy storage capabilities and can be used in the field of thermal insulation materials.

[0180] Example 10

[0181] This embodiment provides a method for preparing a hollow aramid aerogel fiber with a multi-level pore structure, and the specific steps include:

[0182] (1) Heterocyclic aromatic polyamide fiber, sodium ethoxide, N,N-dimethylformamide, and dimethyl sulfoxide (mass ratio: 1:0.1:0.5:8.4) were mixed as spinning solution A, the concentration of heterocyclic aromatic polyamide fiber was 10 wt%, and a 5 wt% agarose / water solution was used as spinning solution B;

[0183] (2) Using a needle with an inner needle outer diameter of 710 μm and an outer needle inner diameter of 1 mm, spinning solution A and spinning solution B were simultaneously extruded into a ferric chloride / water coagulation bath at an extrusion speed of 500 μL / min by a coaxial wet spinning method. The spinning solutions underwent in-situ dynamic sol-gel transformation in the coagulation bath to obtain hollow aramid gel fibers;

[0184] (3) Solvent replacement was performed sequentially with ethanol and n-hexane, followed by drying under normal pressure to obtain hollow aramid aerogel fibers.

[0185] (4) The obtained fiber was immersed in fluorocarbon resin for 24 hours, taken out and dried at normal pressure to obtain a hollow aramid aerogel fiber with a modified multi-level pore structure.

[0186] By observing the multi-level pore structure shown in the electron microscope image, Table 1 shows the multi-level pore structure and pore distribution of the fiber wall of the aerogel fiber provided in this embodiment.

[0187] Figure 11The water contact angles of the hollow aramid aerogel fibers with a hierarchical pore structure obtained in this example before and after modification are shown. As can be seen, the water contact angle increases from 38° to 104.2° after hydrophobic modification, changing from hydrophilic to hydrophobic. The hydrophobic properties of the hydrogel fibers provided in this example, after hydrophobic modification, can also be applied in the field of water-oil separation technology.

[0188] Refer to Table 1, which shows the pore distribution of the multi-level pore structure of the fiber wall of the hollow aramid aerogel fiber with a multi-level pore structure provided in Examples 1 to 10 of the present invention.

[0189] Table 1 Multi-level pore structure distribution of fiber wall provided by the embodiment

[0190]

[0191]

[0192] Table 1 shows the morphology and distribution of the macropore channels of the hollow aramid aerogel fibers with a hierarchical pore structure, as well as the pore levels within the fibers, described in Examples 1-10. Combined with the electron microscopy images of each example, the fiber walls of the hollow aramid aerogel fibers provided by the present invention have a hierarchical pore structure, with macropore channels that are needle-shaped, finger-shaped, or semi-finger-shaped and arranged radially. The fiber walls contain macropore channels larger than 10 μm, sub-macropore channels ranging from 50 nm to 10 μm, mesopore channels ranging from 2 nm to 50 nm, and micropore channels smaller than 2 nm.

[0193] The hollow aramid aerogel fiber with a multi-level pore structure provided by the present invention 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 regulating the pressure difference, flux and selectivity of the medium passing through the tube wall.

[0194] Furthermore, the multi-level pore hollow structure prepared in this embodiment can not only meet the requirements of the oxygenation unit in the oxygenator and be used to make the oxygenator of the artificial lung, but also meet the requirements for waste removal during hemodialysis and can be used in the dialyzer of the artificial kidney.

[0195] At the same time, it has both good adsorption properties and phase change energy storage functions, and can also be used in the fields of water-oil separation, filtration, seawater desalination technology, water treatment technology, and thermal insulation materials.

[0196] Through the technical solutions provided in Examples 1-10, it can be found that the hollow aramid aerogel fiber with a multi-level pore structure provided by the present invention has adjustable fiber inner diameter, outer diameter and wall thickness, as well as the pore size, pore morphology and pore size distribution on the fiber wall. It has a large specific surface area and high porosity, and the preparation process is simple and easy to achieve large-scale production. The prepared products can be widely used in technical fields such as oxygenators, artificial kidneys, water-oil separation, filtration, seawater desalination, water treatment, thermal insulation, etc.

[0197] In addition, the inventors of this case also conducted experiments with other raw materials and conditions listed in this specification, referring to the methods of Examples 1-10, and similarly produced hollow aramid aerogel fibers with a multi-level pore structure in which the fiber inner diameter, outer diameter and wall thickness, as well as the pore size, pore morphology and pore size distribution on the fiber wall can be controlled, with a large specific surface area and high porosity.

[0198] The various aspects, embodiments, features and examples of the present invention should be considered as illustrative in all respects and are not intended to limit the present invention, the scope of which is defined solely by the claims. Other embodiments, modifications and uses will be apparent to those skilled in the art without departing from the spirit and scope of the invention as claimed.

[0199] Throughout this disclosure, where compositions are described as having, containing, or comprising particular components, or where processes are described as having, containing, or comprising particular process steps, it is contemplated that the compositions taught by this disclosure also consist essentially of, or consist of, the recited components, and that the processes taught by this disclosure also consist essentially of, or consist of, the recited process steps.

[0200] Should be understood that, the order of each step or the order in which specific action is performed is not very important, as long as the present invention teachings remain operable.In addition, two or more steps or actions can be performed simultaneously.

[0201] Although the present invention has been described with reference to illustrative embodiments, it will be understood by those skilled in the art that various other changes, omissions, and / or additions may be made and that substantial equivalents may be substituted for elements of the described embodiments without departing from the spirit and scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the present invention without departing from the scope of the invention. Therefore, it is not intended that the present invention be limited to the specific embodiments disclosed for carrying out the invention, but rather that the invention will encompass all embodiments falling within the scope of the appended claims.

Claims

1. A method for preparing a hollow aramid aerogel fiber with a multi-level pore structure, characterized in that: The following steps are involved: At least aramid fiber and a first solvent are uniformly mixed and used as a spinning solution A; Providing spinning solution B; By a coaxial wet spinning method, spinning solution A is used as the shell spinning solution, and spinning solution B is used as the core spinning solution. The spinning solution A and the spinning solution B are simultaneously extruded into a coagulation bath, and the spinning solution A undergoes an in-situ dynamic sol-gel transformation in the coagulation bath to obtain a hollow aramid gel fiber; Subsequently, a solvent replacement-drying process was performed to obtain a hollow aramid aerogel fiber with a multi-level pore structure. Among them, 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 inner needle outer diameter and the outer needle inner diameter is 50 μm~1000 μm.

2. The preparation method according to claim 1, characterized in that In the spinning solution A, the aramid fiber is 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; The first solvent includes any one or a combination of two or more of nitrogen-methyl pyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, methanol, water, acetone, ethanol, and concentrated sulfuric acid; The concentration of the aramid fiber is 0.1-30 wt%; and / or, the spinning solution B comprises a second solvent with or without an added solute; The solute is 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 or a combination of two or more of water, ethanol, acetone, nitrogen-methyl pyrrolidone, ethyl acetate, acetonitrile, dimethyl sulfoxide, glycerol, dimethyl silicone oil, and N,N-dimethylformamide; and / or, the coagulation bath comprises a third solvent with or without added auxiliary components; The third solvent is any one or a combination of two or more of water, ethanol, acetone, dimethyl sulfoxide, nitrogen methyl pyrrolidone, ethyl acetate, dimethyl silicone oil, N,N-dimethylformamide, glycerol, and tert-butanol; The auxiliary component is any one or a combination of two or more of calcium chloride, ferric chloride, silver ions, copper ions, hydrochloric acid, sulfuric acid, and acetic acid.

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

4. The preparation method according to claim 1, characterized in that The solvent replacement comprises immersing the hollow aramid gel fiber in a replacement solvent for replacement; the replacement solvent is one or a combination of two or more of water, ethanol, tert-butanol, n-hexane, hexafluoroisopropanol, cyclohexane, and acetone; The drying process includes any one of freeze drying, supercritical fluid drying, and normal pressure drying, or a combination of two or more thereof; The temperature of the freeze-drying cold trap is -80~15°C, and the vacuum degree is less than 0.1 kPa; The supercritical fluid in the supercritical fluid drying includes any one of supercritical CO2, supercritical methanol and supercritical ethanol, or a combination of two or more thereof.

5. The preparation method according to any one of claims 1 to 4, characterized in that The spinning solution A further includes additives; 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, polyvinyl pyrrolidone, dibutyl phthalate, and glycerol; The mass ratio of the first additive to the aramid fiber is 0.1 to 1:1; The mass ratio of the second additive to the aramid fiber is 0.2-2:

1.

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

7. The hollow aramid aerogel fiber with a multi-level pore structure according to claim 6, characterized in that: The multi-level pore structure includes macroporous channels, sub-macroporous channels, mesoporous channels and microporous channels; wherein the macroporous channels are perpendicular to the fiber wall and arranged radially.

8. The hollow aramid aerogel fiber with a multi-level pore structure according to claim 7, characterized in that: The macroporous channel is in the shape of a finger-shaped through-hole structure, or a needle-shaped or semi-finger-shaped semi-through-hole structure; The through-hole structure is arranged radially from the inner wall to the outer wall; The semi-through hole structure is located on one side of the fiber wall, or on the inner side and the outer side of the fiber wall, and has a symmetrical structure.

9. The hollow aramid aerogel fiber with a multi-level pore structure according to claim 7, characterized in that: The multi-level pore structure includes sub-macroporous channels, mesoporous channels and microporous channels.

10. The hollow aramid aerogel fiber with a multi-level pore structure according to claim 7, characterized in that: The hollow aramid aerogel fiber with a 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 an aspect ratio greater than 10.

11. The hollow aramid aerogel fiber with a multi-level pore structure according to claim 7, characterized in that: The hollow aramid aerogel fiber with a 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 hollow aramid aerogel fiber with a modified hierarchical pore structure, obtained by post-treating the hollow aramid aerogel fiber with a hierarchical pore structure obtained by the preparation method according to any one of claims 1 to 5, or the hollow aramid aerogel fiber with a hierarchical pore structure according to any one of claims 6 to 10; The post-treatment includes any one of heat treatment, hydrophobic treatment, and filling modification, or a combination of two or more thereof.

13. The hollow aramid aerogel fiber with a modified multi-level pore structure according to claim 11, characterized in that: The heat treatment method includes directly placing the hollow aramid aerogel fiber with a multi-level pore structure in a tubular furnace and subjecting it to high-temperature treatment for 30 minutes to 6 hours under a specific atmosphere; the specific atmosphere is any one of nitrogen, argon, and air; and the heat treatment temperature is 80-450°C.

14. The hollow aramid aerogel fiber with a modified multi-level pore structure according to claim 11, characterized in that: The hydrophobic treatment method comprises directly immersing the hollow aramid aerogel fiber with a multi-level pore structure in a hydrophobic coating solution for 3 seconds to 1 hour, and then taking it out and vacuum drying it at room temperature and pressure or at 30 to 150° C. for 10 minutes to 72 hours; 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.

15. The hollow aramid aerogel fiber with a modified multi-level pore structure according to claim 11, characterized in that: The filling and modification method comprises immersing the hollow aramid aerogel fiber with a multi-level pore structure in a functional liquid material for 30 minutes to 24 hours, taking it out and placing it naturally; The functional liquid material includes any one of polyethylene glycol, liquid paraffin, polyol, dimethyl silicone oil, and perfluoropolyether, or a combination of two or more thereof.

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

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