A method for improving the bulk of a cloud wool fiber

Abstract

The application relates to a preparation method for improving the bulkiness of cloud wool fibers, and relates to the technical field of fiber material preparation, which comprises the following steps: preparing a primary gel; preparing a secondary crosslinking gel through step-by-step crosslinking of sodium silicate and a covalent organic framework material; preparing a fiber template through electrospinning, placing the secondary crosslinking gel on the fiber template, pressurizing, and obtaining a gel template composite; immersing the fiber template composite in a 1,3,5-triformylbenzene solution, heating and reacting, and obtaining a semi-finished product; performing gradient solvent replacement on the semi-finished product, performing modification treatment on the semi-finished product by using a hexadecyl trimethoxysilane solution, and obtaining a modified semi-finished product; and adopting gradient temperature elevation normal-pressure drying on the modified semi-finished product, and obtaining aerogel cloud wool fibers. The application has the effects of improving the bulkiness and heat insulation and preservation performance of the cloud wool fibers, the fiber density is low, and the cloud wool fibers have good lightness.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of fiber material preparation, in particular to a preparation method for improving the bulkiness of cloud fiber. BACKGROUND

[0002] As a new type of nanoporous material, aerogel cloud fiber has a wide application prospect in the fields of energy saving and environmental protection, aerospace, building insulation, etc. due to its unique three-dimensional network structure, low density and excellent thermal insulation performance. The interconnected nanopores in the interior can effectively inhibit gas convection and heat conduction, and at the same time, the material has the characteristics of lightweight and high porosity, and is considered as an ideal candidate for the next generation of high-performance thermal insulation materials. However, the existing aerogel cloud fiber often has a dense pore structure due to insufficient bulkiness in practical application, which weakens its thermal insulation, sound absorption and other functional properties, and limits the deep development and large-scale application of the material performance.

[0003] At present, the mainstream preparation technology of aerogel cloud fiber is based on sol-gel method, which forms a three-dimensional gel network by adjusting the chemical reaction of the precursor solution, and combines with supercritical drying technology to remove the solvent to maintain the integrity of the porous structure. Researchers try to reduce the density of the material while enhancing the stability of the pore structure by optimizing the gelation rate, adjusting the solvent composition and improving the drying process. In addition, some methods introduce templates or composite reinforcing phases to improve the mechanical properties of the network skeleton, but the process complexity and cost problems are still outstanding.

[0004] Although the existing preparation technology has made certain progress, there are still significant challenges in improving the bulkiness of aerogel cloud fiber. The gel shrinkage and structure collapse phenomenon in the traditional process is difficult to completely avoid, which leads to the difficulty in accurately controlling the porosity and pore size distribution, directly affecting the lightweight and functional performance of the material, and needs to be improved. SUMMARY

[0005] In order to improve the bulkiness of cloud fiber, the application provides a preparation method for improving the bulkiness of cloud fiber.

[0006] The preparation method for improving the bulkiness of cloud fiber provided by the application adopts the following technical scheme:

[0007] The preparation method for improving the bulkiness of cloud fiber comprises the following steps:

[0008] S1, dissolving a polymer material in a solvent to obtain a sol, treating by freeze-thaw cycle, soaking and drying to obtain a primary gel; the polymer material comprises cellulose acetate;

[0009] S2, dissolving sodium silicate in a solvent, adjusting pH to be acidic, after heating and stirring, an aerogel precursor is obtained; immersing the primary gel into the aerogel precursor solution, heating and stirring to react, a primary crosslinked gel is obtained; mixing the covalent organic framework material suspension and the primary crosslinked gel, heating and stirring to react, a secondary crosslinked gel is obtained;

[0010] S3, electrospinning the polyacrylonitrile spinning solution, after soaking and drying, a fiber template is obtained; placing the secondary crosslinked gel on the fiber template, pressurizing to obtain a gel template composite; immersing the gel template composite into a 1, 3, 5-triformylbenzene solution, heating to react, a semi-finished product is obtained;

[0011] S4, performing gradient solvent replacement on the semi-finished product, after replacement, immersing into a hexadecyltrimethoxysilane solution, heating to react, after washing and drying, a modified semi-finished product is obtained;

[0012] S5, using gradient temperature increase atmospheric pressure drying the modified semi-finished product, an aerogel cloud fiber is obtained.

[0013] Through freeze-thaw cycle to induce cellulose acetate sol to form a hierarchical porous structure, combined with the hydrogen bond crosslinking of the silica nanoparticles generated by the acid hydrolysis of sodium silicate and the primary gel to construct a rigid skeleton, then introducing the covalent organic framework material to realize secondary crosslinking through dynamic covalent bond, forming an inorganic-organic synergistic network to improve porosity; the polyacrylonitrile fiber template produced by electrospinning provides a micron-level skeleton structure, and the covalent organic framework material epitaxially grown forms a sub-micron pore, constructing a hierarchical channel of micropore, mesopore and macropore to improve the specific surface area; gradient solvent replacement and hydrophobic modification of hexadecyltrimethoxysilane can effectively inhibit the pore collapse caused by capillary stress, and the step-by-step atmospheric pressure drying retains the pore integrity, and the mutual synergistic effect of each component and step reduces the density of the cloud fiber and improves the loftiness and thermal insulation performance.

[0014] Preferably, the freezing and thawing cycle treatment in the S1 step is 3-5 times of freezing and thawing cycle at-20-25℃, cooling to 0℃ at a rate of 1.5-2.5℃ / min, cooling to-20℃ at a rate of 0.5-1.5℃ / min, freezing for 4-8h, heating to 0℃ at a rate of 0.5-1.5℃ / min, heating to 25℃ at a rate of 1-2℃ / min, thawing for 2-4h.

[0015] Under the above freezing and thawing rate, the water in the fiber undergoes repeated freezing and thawing process, and the periodic expansion and contraction of ice crystals form multi-level through pores in the fiber network, while inducing dynamic reorganization of molecular chain segments, building a stable three-dimensional interpenetrating network structure; the mechanical stress generated by ice crystal growth can weaken the dense connection between fibers, and the gradient temperature rise and fall strategy can avoid pore collapse by regulating ice crystal size and distribution, finally forming a high specific surface area, low density fluffy system, reducing the density of the cloud wool fiber, and improving the loftiness and thermal insulation performance of the cloud wool fiber.

[0016] Preferably, the polymer material further comprises chitosan.

[0017] By introducing chitosan and cellulose acetate, the abundant amino groups in the chitosan molecular chain and the hydroxyl groups of cellulose acetate synergistically form hydrogen bonds and electrostatic crosslinking networks, guiding the directional growth of ice crystals along the fiber axis during the freeze-thaw cycle, forming a through micro-nano pore network, enhancing the flexibility and structural stability of the gel skeleton, and inhibiting pore collapse; the cationic property of chitosan can adsorb silicate ions generated by the hydrolysis of sodium silicate, promoting the uniform distribution of inorganic nanoparticles in the gel pores, while its natural antibacterial property endows the fiber with antibacterial function; chitosan can also dynamically interact with covalent organic framework materials to form dynamic covalent bonds, further optimizing the pore connectivity, achieving the improvement of the lightness and loftiness of the cloud wool fiber.

[0018] Preferably, the mass ratio of cellulose acetate and chitosan in the polymer material is (2-3):1.

[0019] The polymer material compounded according to the above mass ratio can effectively improve the lightness, loftiness and thermal insulation performance of the cloud wool fiber.

[0020] Preferably, the chitosan is modified and prepared by the following steps:

[0021] Add 2,3-epoxypropyltrimethylammonium chloride solution to the chitosan solution, adjust the pH to alkaline, heat and stir in water bath, after the reaction is completed, alcohol precipitation, centrifugation, washing, dialysis and drying to obtain quaternized chitosan.

[0022] Quaternization modification of chitosan introduces high-density positive charge groups, which effectively improves the loftiness of the cloud fiber through the synergistic effect of electrostatic repulsion and enhanced molecular chain flexibility. The cationically modified chitosan molecular chain exhibits an extended conformation in aqueous solution, which weakens the dense accumulation between fibers through charge repulsion, and forms a gradient crosslinking network with the fiber matrix through its dynamic hydrogen bond network, giving the pore structure the ability to self-adaptively adjust. In the freezing and thawing phase change process, the strong electrostatic adsorption of quaternary ammonium groups and the negative charge on the fiber surface guides the directional growth of ice crystals, and builds through multi-level pores. The solvent effect of quaternary ammonium chitosan reduces the tendency of pore closure by optimizing the interfacial wettability, and finally forms stable and fluffy cloud fibers with high specific surface area and low thermal conductivity.

[0023] Preferably, the mass ratio of the primary gel, sodium silicate and covalent organic framework material in step S2 is 1:0.25:(0.005-0.015).

[0024] The gel prepared according to the above mass ratio has a good pore structure, which can effectively improve the lightness, loftiness and thermal insulation performance of the cloud fiber.

[0025] Preferably, the reaction conditions of the preliminary cross-linked gel in step S2 are 40-60℃ for 6-8h, and intermittent oscillation reaction.

[0026] The preliminary cross-linked gel improves the loftiness of the cloud fiber through a dynamic network construction and energy dissipation mechanism. In a suitable temperature environment, the thermal motion of the polymer molecular chain segment is enhanced, which promotes the directional bonding of sodium silicate and the fiber surface active group. The periodic shear force generated by intermittent oscillation reduces the diffusion resistance by disturbing the solution interface, so that the cross-linking reaction is uniformly distributed in three-dimensional space to form a gradient cross-linking network. This dynamic reaction process regulates the spatial arrangement of cross-linking sites through energy dissipation strategy, which not only retains the flexible motion ability of the molecular chain to construct through pores, but also disperses stress concentration through the reversible bond breaking-recombination mechanism, forming an interpenetrating network structure with high porosity and anti-collapse ability, thereby improving the lightness, loftiness and thermal insulation performance of the cloud fiber.

[0027] Preferably, the reaction conditions of the secondary cross-linked gel in step S2 are to mix the covalent organic framework material suspension into the preliminary cross-linked gel, add urea as a dynamic cross-linking agent, stir at 30-50℃ for 3-5h, heat to 75-85℃ at a heating rate of 1.5-2.5℃ / min, and react for 6-8h.

[0028] The rigid porous framework of the covalent organic framework material forms an interpenetrating structure with the gel network, and a gradient pore is constructed through the synergistic effect of dynamic hydrogen bonds and reversible imine bonds; the amino group of urea is reversibly bonded to the surface active site of the covalent organic framework material during the temperature rising process; the process realizes dual-network construction through phased temperature regulation, and the flexible hydrogen bond network is preferentially formed at a low temperature stage to maintain the pore connectivity, and the framework rigidity is enhanced at a high temperature stage through urea-mediated covalent crosslinking; urea, as a dynamic crosslinking agent, cooperates with the covalent organic framework material to guide the formation of a three-dimensional support topological structure between fibers, adjusts the interfacial wettability through the solvation effect, and inhibits pore closure during the phase transition, thereby improving the lightness and loftiness of the fibers.

[0029] Preferably, lithium chloride is added to the polyacrylonitrile spinning solution in step S3 in a mass fraction of 1-3%.

[0030] The lithium ions generated by the ionization of lithium chloride weaken the dipole-dipole interaction between the polyacrylonitrile molecular chains through the electrostatic shielding effect, reduce the solution viscosity and enhance the flowability, so that the spinning solution is more easily formed into a stable jet under a high-voltage electric field and the fiber diameter is finely controlled; the dynamic coordination between the lithium ions and the cyano groups of polyacrylonitrile induces the directional arrangement of the molecular chains along the electric field direction, and a multi-level pore structure is formed during the fiber solidification process; and the chloride ions improve the surface charge density of the jet by enhancing the solution conductivity, promote the electrostatic repulsion during the fiber deposition, inhibit the dense accumulation and construct a three-dimensional through-pore network, and improve the porosity of the fiber template.

[0031] Preferably, the electrospinning conditions in step S3 are a voltage of 15-18 kV, a push-injection speed of 1-1.5 mL / h, and a receiving distance of 15-20 cm.

[0032] The electric field force excited in the medium voltage range forms a dynamic balance with the surface tension of the solution, induces the jet to form a stable Taylor cone and realizes uniform stretching, and inhibits the dense accumulation between fibers through the charge repulsion during the fiber solidification process; the moderate push-injection speed makes the solution supply match the solvent evaporation rate, avoids the jet breakage or the generation of beaded defects, and prolongs the orientation arrangement time of the molecular chains along the electric field direction, thereby promoting the gradient formation of the nanoscale pores; the optimized receiving distance regulates the solvent evaporation gradient and the fiber deposition dynamics, forms a through three-dimensional network structure in the fiber, and cooperates with the synergistic effect of electrostatic adsorption and air turbulence to enhance the elastic support and air layer retention capacity between fibers; through the synergistic conversion of electric field energy-mechanical energy-interfacial energy, the fiber diameter, porosity and structural rigidity are simultaneously optimized, and the lightness, loftiness and thermal insulation performance of the cloud-wool fiber are improved.

[0033] In summary, the present application includes at least one of the following beneficial technical effects:

[0034] 1. Through freeze-thaw cycles to induce cellulose acetate sol formation of hierarchical porous structure, combined with the silica nanoparticles generated by sodium silicate acid hydrolysis and primary gel hydrogen bond crosslinking to build rigid skeleton, followed by the introduction of covalent organic framework material through dynamic covalent bond to realize secondary crosslinking, form inorganic-organic synergistic network, improve porosity; electrospinning polyacrylonitrile fiber template provides micron skeleton structure, epitaxial growth of covalent organic framework material forms submicron pores, constructs hierarchical channels of microporous, mesoporous and macroporous, and improves specific surface area; gradient solvent replacement and hydrophobic modification of hexadecyl trimethoxysilane can effectively inhibit the pore collapse caused by capillary stress, ladder type atmospheric drying retains the integrity of the pores, and the mutual synergistic effect of each component and step reduces the density of the cloud wool fiber and improves the loftiness and thermal insulation performance.

[0035] 2. By introducing chitosan and cellulose acetate, the abundant amino groups in the chitosan molecular chain and the hydroxyl groups of cellulose acetate synergistically form a hydrogen bond and electrostatic crosslinking network, guiding the directional growth of ice crystals along the fiber axis during freeze-thaw cycles to form a through micro-nano porous network, enhancing the flexibility and structural stability of the gel skeleton and inhibiting pore collapse; the cationic nature of chitosan can directionally adsorb silicate ions generated by sodium silicate hydrolysis, promoting the uniform distribution of inorganic nanoparticles in the gel pores, and its natural antibacterial property endows the fiber with antibacterial function; chitosan can also dynamically interact with covalent organic framework materials to form dynamic covalent bonds, further optimizing the pore connectivity and achieving the improvement of the lightness and loftiness of the cloud wool fiber.

[0036] 3. The quaternization modification of chitosan introduces high-density positive charge groups, which effectively improves the loftiness of the cloud wool fiber through the synergistic effect of electrostatic repulsion and enhanced molecular chain flexibility; the expanded conformation of the cationically modified chitosan molecular chain in aqueous solution weakens the dense packing between fibers through charge repulsion, while its dynamic hydrogen bond network forms a gradient crosslinking with the fiber matrix, giving the pore structure the ability to adaptively adjust; in the freeze-thaw phase change process, the strong electrostatic adsorption of quaternary ammonium groups and the negative charge on the fiber surface guides the directional growth of ice crystals, building a through multi-stage pore, while the solvation effect of quaternized chitosan reduces the pore closure trend by optimizing the interfacial wettability, ultimately forming a stable and fluffy cloud wool fiber with high specific surface area and low thermal conductivity. DETAILED DESCRIPTION

[0037] The application discloses a preparation method for improving the loftiness of cloud wool fiber. The raw materials used in the application can be obtained through market-purchased raw materials, except for special instructions. The application is further described in detail in combination with the embodiments as follows:

[0038] Raw materials: cellulose acetate (CAS No. 9004-35-7) was purchased from Nanjing Chemical Reagent Co., Ltd., COF-LZU1 was purchased from Xi'an Qiyue Biological Technology Co., Ltd., sodium silicate (CAS No. 1344-09-8), urea (CAS No. 57-13-6), polyacrylonitrile (CAS No. 25014-41-9) with molecular weight of 150,000 was purchased from Wuhan Smake Biological Technology Co., Ltd., 1,3,5-triformylbenzene (CAS No. 3163-76-6), hexadecyltrimethoxysilane (CAS No. 16415-12-6), chitosan (CAS No. 9012-76-4) with deacetylation degree of 95% was purchased from Shandong Fentai Biological Technology Co., Ltd., 2,3-epoxypropyltrimethylammonium chloride (CAS No. 3033-77-0).

[0039] Example 1

[0040] The polymer material was cellulose acetate, and the covalent organic framework material was COF-LZU1.

[0041] S1, the polymer material was added to a 10% sodium hydroxide aqueous solution, and the mass ratio of the polymer material to the sodium hydroxide aqueous solution was 1:10, and stirring was performed at a speed of 200 rpm until complete dissolution to obtain a sol; the sol was subjected to freeze-thaw cycle treatment, and the temperature was lowered to 0°C at a rate of 1.5°C / min, and then lowered to -20°C at a rate of 0.5°C / min, and frozen for 4 h; then the temperature was raised to 0°C at a rate of 0.5°C / min, and then raised to 25°C at a rate of 1°C / min, and thawed for 2 h, and the cycle was repeated 5 times; the freeze-thaw treated gel was soaked in deionized water for 1 d, and vacuum dried at 60°C to obtain a primary gel;

[0042] S2, the mass ratio of the primary gel, sodium silicate and covalent organic framework material was 1:0.25:0.005; the sodium silicate was dissolved in deionized water to prepare a 0.5 mol / L solution, and the pH was adjusted to 4.5 using dilute sulfuric acid, and the solution was stirred at 80°C at a speed of 200 rpm for 2 h to obtain an aerogel precursor; the primary gel was immersed in the aerogel precursor solution, and intermittent oscillation was performed at 40°C for 8 h (oscillation frequency 30 rpm, oscillation for 5 min every 30 min) to obtain a preliminary crosslinked gel; a 2% covalent organic framework material suspension (solvent: ethanol and tetrahydrofuran at a volume ratio of 7:3) was mixed with 1% urea based on the total mass of the suspension, and after ultrasonic treatment, a mixed suspension was obtained, which was added to the preliminary crosslinked gel, and stirred at 30°C at a speed of 200 rpm for 5 h, and then the temperature was raised to 85°C at a rate of 1.5°C / min, and reacted for 6 h to obtain a secondary crosslinked gel;

[0043] S3, dissolve lithium chloride in DMF, add polyacrylonitrile, configure into a spinning solution with a mass concentration of 10% polyacrylonitrile + 1% lithium chloride, voltage 18 kV, push-in speed 1.5 mL / h, receiving distance 15 cm, ambient humidity less than 40%, electrospinning, then soak in ethanol for 12 h, vacuum dry at 60℃, obtain fiber template; cut the secondary crosslinked gel into 2 mm slices, lay on the surface of the fiber template, press 0.2 MPa for 3 h, obtain gel template composite; immerse the gel template composite in 1,3,5-triformylbenzene solution (0.2 mol / L, solvent is a mixed solvent of ethanol and acetic acid with a volume ratio of 10:1), react at 80℃ for 12 h, obtain semi-finished product;

[0044] S4, immerse the semi-finished product in water, ethanol and tert-butanol in turn, replace each solvent for 3 times, each time for 2 h, after replacement, immerse in a 5% hexadecyltrimethoxysilane ethanol solution, adjust pH to 5 with acetic acid, react at 60℃ for 8 h, wash with n-hexane for 3 times, vacuum dry at 60℃ for 2 h, obtain modified semi-finished product;

[0045] S5, use gradient temperature constant pressure drying to modify the semi-finished product, place the modified semi-finished product in a constant pressure drying oven, heat at 40℃ for 2 h, heat at 60℃ for 4 h, heat at 80℃ until constant weight, heating rate 1.5℃ / min, obtain aerogel cloud fiber.

[0046] Example 2

[0047] The polymer material is cellulose acetate, and the covalent organic framework material is COF-LZU1.

[0048] S1, add the polymer material to a 10% sodium hydroxide aqueous solution, the mass ratio of the polymer material to the sodium hydroxide aqueous solution is 1:10, stir at a speed of 200 rpm until completely dissolved, obtain sol; freeze-thaw cycle treatment is performed on the sol, cool down to 0℃ at a rate of 2.5℃ / min, cool down to -20℃ at a rate of 1.5℃ / min, freeze for 8 h; then warm up to 0℃ at a rate of 1.5℃ / min, warm up to 25℃ at a rate of 2℃ / min, thaw for 4 h, cycle for 3 times; immerse the freeze-thaw treated gel in deionized water for 1 d, vacuum dry at 60℃, obtain primary gel;

[0049] S2, the mass ratio of the primary gel, sodium silicate and covalent organic framework material is 1:0.25:0.015; the sodium silicate is dissolved in deionized water to configure a 0.5 mol / L solution, the pH is adjusted to 4.5 by using dilute sulfuric acid, and the reaction is carried out at 80℃ under stirring at a speed of 200 rpm for 2 h to obtain an aerogel precursor; the primary gel is immersed in the aerogel precursor solution, and the reaction is carried out at 60℃ under intermittent oscillation for 6 h (oscillation frequency 30 rpm, oscillation for 5 min every 30 min) to obtain a preliminary cross-linked gel; a covalent organic framework material suspension (solvent: ethanol and tetrahydrofuran in a volume ratio of 7:3) with a mass concentration of 2% is mixed with 1% urea based on the total mass of the suspension, and after ultrasonic treatment, a mixed suspension is obtained, which is added to the preliminary cross-linked gel, and the reaction is carried out at 50℃ under stirring at a speed of 200 rpm for 3 h, and then the temperature is raised to 75℃ at a temperature raising rate of 2.5℃ / min, and the reaction is carried out at 75℃ for 8 h to obtain a secondary cross-linked gel;

[0050] S3, lithium chloride is dissolved in DMF, polyacrylonitrile is added to configure a spinning solution with a mass concentration of 10% polyacrylonitrile + 3% lithium chloride, electrospinning is carried out at a voltage of 15 kV and a push-in speed of 1 mL / h, a receiving distance of 20 cm and an ambient humidity of less than 40%, then the obtained fibers are soaked in ethanol for 12 h and vacuum dried at 60℃ to obtain a fiber template; the secondary cross-linked gel is cut into 2 mm slices, which are laid on the surface of the fiber template and pressed at a pressure of 0.2 MPa for 3 h to obtain a gel template composite; the gel template composite is immersed in a 1,3,5-triformylbenzene solution (0.2 mol / L, solvent: a mixed solvent of ethanol and acetic acid in a volume ratio of 10:1), and the reaction is carried out at 80℃ for 12 h to obtain a semi-finished product;

[0051] S4, the semi-finished product is sequentially soaked in water, ethanol and tert-butanol, each solvent is replaced for 3 times, and each soaking is carried out for 2 h, after replacement, the semi-finished product is immersed in a 5% hexadecyltrimethoxysilane ethanol solution, the pH is adjusted to 5 by using acetic acid, the reaction is carried out at 60℃ for 8 h, the semi-finished product is washed with n-hexane for 3 times, and vacuum drying is carried out at 60℃ for 2 h to obtain a modified semi-finished product;

[0052] S5, the modified semi-finished product is subjected to gradient temperature raising and normal pressure drying, the modified semi-finished product is placed in a normal pressure drying oven, and the temperature is raised at a rate of 1.5℃ / min to obtain an aerogel velvet fiber.

[0053] Example 3

[0054] The polymer material is cellulose acetate, and the covalent organic framework material is COF-LZU1.

[0055] S1, the polymer material is added to the aqueous solution of sodium hydroxide with a mass concentration of 10%, the mass ratio of the polymer material and the aqueous solution of sodium hydroxide is 1:10, and stirring is performed at a speed of 200 rpm until complete dissolution to obtain a sol; the sol is subjected to freeze-thaw cycle treatment, is cooled to 0℃ at a speed of 2℃ / min, is cooled to -20℃ at a speed of 1℃ / min, is frozen for 6 h, is then warmed to 0℃ at a speed of 1℃ / min, is further warmed to 25℃ at a speed of 1.5℃ / min, is thawed for 3 h, and the cycle is repeated 4 times; the gel after freeze-thaw treatment is soaked in deionized water for 1 d, is vacuum dried at 60℃, and a primary gel is obtained;

[0056] S2, the mass ratio of the primary gel, sodium silicate and covalent organic framework material is 1:0.25:0.01; the sodium silicate is dissolved in deionized water to prepare a 0.5 mol / L solution, dilute sulfuric acid is used to adjust the pH to 4.5, stirring is performed at a speed of 200 rpm at 80℃ for 2 h, and an aerogel precursor is obtained; the primary gel is immersed in the aerogel precursor solution, intermittent oscillation reaction is performed at 50℃ for 7 h (oscillation frequency 30 rpm, oscillation for 5 min every 30 min), and a primary crosslinked gel is obtained; a covalent organic framework material suspension with a mass concentration of 2% (solvent: ethanol and tetrahydrofuran at a volume ratio of 7:3) is mixed with 1% urea based on the total mass of the suspension, a mixed suspension is obtained after ultrasonic treatment, and the primary crosslinked gel is added, stirring is performed at a speed of 200 rpm at 40℃ for 4 h, the temperature is increased to 80℃ at a speed of 2℃ / min, and reaction is performed at 80℃ for 7 h, and a secondary crosslinked gel is obtained;

[0057] S3, lithium chloride is dissolved in DMF, polyacrylonitrile is added, a spinning solution with a mass concentration of 10% polyacrylonitrile + 2% lithium chloride is prepared, electrospinning is performed at a voltage of 16.5 kV and a push-in speed of 1.25 mL / h, the receiving distance is 17.5 cm, the environmental humidity is less than 40%, the fiber template is obtained after immersion in ethanol for 12 h and vacuum drying at 60℃, the secondary crosslinked gel is cut into 2 mm slices, is laid on the surface of the fiber template, and is pressed at a pressure of 0.2 MPa for 3 h, and a gel template composite is obtained; the gel template composite is immersed in a 1, 3, 5-triformylbenzene solution (0.2 mol / L, solvent: a mixed solvent of ethanol and acetic acid at a volume ratio of 10:1), and a semi-finished product is obtained after reaction at 80℃ for 12 h;

[0058] S4, the semi-finished product is sequentially immersed in water, ethanol and tert-butanol, each solvent is replaced 3 times, each immersion is performed for 2 h, after replacement, the semi-finished product is immersed in a 5% hexadecyltrimethoxysilane ethanol solution, acetic acid is used to adjust the pH to 5, reaction is performed at 60℃ for 8 h, the semi-finished product is washed with n-hexane 3 times, and vacuum drying is performed at 60℃ for 2 h, and a modified semi-finished product is obtained;

[0059] S5, the modified semi-finished product is placed in a normal pressure drying oven, and is kept at 40 DEG C for 2 h, kept at 60 DEG C for 4 h, and kept at 80 DEG C until the weight is constant, the heating rate is 1.5 DEG C / min, and aerogel cloud wool fibers are obtained.

[0060] Example 4

[0061] Example 4 is based on Example 3, and the difference between Example 4 and Example 3 is that the number of freeze-thaw cycle treatments in Example 4 is 1.

[0062] Example 5

[0063] Example 5 is based on Example 3, and the difference between Example 5 and Example 3 is that the number of freeze-thaw cycle treatments in Example 5 is 6.

[0064] Example 6

[0065] Example 6 is based on Example 3, and the difference between Example 6 and Example 3 is that the mass ratio of the primary gel, sodium silicate and covalent organic framework material in Example 6 is 1:0.25:0.002.

[0066] Example 7

[0067] Example 7 is based on Example 3, and the difference between Example 7 and Example 3 is that the mass ratio of the primary gel, sodium silicate and covalent organic framework material in Example 7 is 1:0.25:0.02.

[0068] Example 8

[0069] Example 8 is based on Example 3, and the difference between Example 8 and Example 3 is that the reaction condition of the preliminary crosslinking gel in step S2 is changed in Example 8.

[0070] S2, sodium silicate is dissolved in deionized water to configure a 0.5 mol / L solution, dilute sulfuric acid is used to adjust the pH to 4.5, and the primary gel is immersed in the aerogel precursor solution at a solid-liquid ratio of 1:10 (g / L) and is subjected to intermittent oscillation reaction at 30 DEG C for 10 h (oscillation frequency 30 rpm, oscillation for 5 min every 30 min), to obtain a preliminary crosslinking gel; a covalent organic framework material suspension with a mass concentration of 2% (solvent: ethanol and tetrahydrofuran at a volume ratio of 7:3) is mixed with 1% of urea based on the total mass of the suspension, and after ultrasonic treatment, a mixed suspension is obtained, which is added to the preliminary crosslinking gel, and the mass ratio of the preliminary crosslinking gel and the mixed suspension is 1:0.5, and the preliminary crosslinking gel is subjected to stirring reaction at 40 DEG C at a speed of 200 rpm for 4 h, and is heated to 80 DEG C at a heating rate of 2 DEG C / min, and is reacted for 7 h, to obtain a secondary crosslinking gel.

[0071] Example 9

[0072] Example 9 is based on Example 3, the difference between Example 9 and Example 3 is only that the reaction conditions of the preliminary cross-linking gel in step S2 are changed in Example 9.

[0073] S2, sodium silicate was dissolved in deionized water to form a 0.5 mol / L solution, the pH was adjusted to 4.5 using dilute sulfuric acid, and the reaction was stirred at 80°C at a speed of 200 rpm for 2 h to obtain an aerogel precursor; the primary gel was immersed in the aerogel precursor solution, the solid-liquid ratio was 1:10 (g / L), and the reaction was intermittently oscillated at 80°C for 4 h (oscillation frequency 30 rpm, oscillation for 5 min every 30 min) to obtain a preliminary cross-linking gel; a covalent organic framework material suspension with a mass concentration of 2% (solvent: ethanol and tetrahydrofuran at a volume ratio of 7:3) was mixed with urea accounting for 1% of the total mass of the suspension, and after ultrasonic treatment, a mixed suspension was obtained, which was added to the preliminary cross-linking gel, the mass ratio of the preliminary cross-linking gel to the mixed suspension was 1:0.5, and the reaction was stirred at 40°C at a speed of 200 rpm for 4 h, and then the temperature was increased to 80°C at a rate of 2°C / min, and the reaction was continued for 7 h to obtain a secondary cross-linking gel.

[0074] Example 10

[0075] Example 10 is based on Example 3, the difference between Example 10 and Example 3 is only that the secondary cross-linking gel in step S2 in Example 10 does not undergo a stepwise temperature increase reaction.

[0076] S2, sodium silicate was dissolved in deionized water to form a 0.5 mol / L solution, the pH was adjusted to 4.5 using dilute sulfuric acid, and the reaction was stirred at 80°C at a speed of 200 rpm for 2 h to obtain an aerogel precursor; the primary gel was immersed in the aerogel precursor solution, the solid-liquid ratio was 1:10 (g / L), and the reaction was intermittently oscillated at 50°C for 7 h (oscillation frequency 30 rpm, oscillation for 5 min every 30 min) to obtain a preliminary cross-linking gel; a covalent organic framework material suspension with a mass concentration of 2% (solvent: ethanol and tetrahydrofuran at a volume ratio of 7:3) was mixed with urea accounting for 1% of the total mass of the suspension, and after ultrasonic treatment, a mixed suspension was obtained, which was added to the preliminary cross-linking gel, the mass ratio of the preliminary cross-linking gel to the mixed suspension was 1:0.5, and the reaction was stirred at 80°C at a speed of 200 rpm for 12 h to obtain a secondary cross-linking gel.

[0077] Example 11

[0078] Example 11 is based on Example 3, the difference between Example 11 and Example 3 is only that lithium chloride is not added in step S3 in Example 11.

[0079] S3, polyacrylonitrile is dissolved in DMF to prepare a polyacrylonitrile spinning solution with a mass concentration of 10%, a voltage of 16.5 kV, a push-in speed of 1.25 mL / h, a receiving distance of 17.5 cm, and an ambient humidity of less than 40%, electrospinning is performed, then the electrospun fibers are soaked in ethanol for 12 h, vacuum dried at 60°C, and a fiber template is obtained; the secondary crosslinked gel is cut into 2 mm slices, laid on the surface of the fiber template, and pressed at a pressure of 0.2 MPa for 3 h to obtain a gel template composite; the gel template composite is immersed in a 1,3,5-triformylbenzene solution (0.2 mol / L, solvent: a mixed solvent of ethanol and acetic acid with a volume ratio of 10:1), and reacted at 80°C for 12 h to obtain a semi-finished product.

[0080] Example 12

[0081] Example 12 is based on Example 3, and the only difference between Example 12 and Example 3 is that in Example 12, 5% lithium chloride based on the total mass of the spinning solution is added in step S3.

[0082] S3, polyacrylonitrile is dissolved in DMF to prepare a polyacrylonitrile spinning solution with a mass concentration of 10%, a voltage of 16.5 kV, a push-in speed of 1.25 mL / h, a receiving distance of 17.5 cm, and an ambient humidity of less than 40%, electrospinning is performed, then the electrospun fibers are soaked in ethanol for 12 h, vacuum dried at 60°C, and a fiber template is obtained; the secondary crosslinked gel is cut into 2 mm slices, laid on the surface of the fiber template, and pressed at a pressure of 0.2 MPa for 3 h to obtain a gel template composite; the gel template composite is immersed in a 1,3,5-triformylbenzene solution (0.2 mol / L, solvent: a mixed solvent of ethanol and acetic acid with a volume ratio of 10:1), and reacted at 80°C for 12 h to obtain a semi-finished product.

[0083] Example 13

[0084] Example 13 is based on Example 3, and the only difference between Example 13 and Example 3 is that in Example 13, the polymer material in step S1 further comprises chitosan, and the mass ratio of cellulose acetate to chitosan is 2:1.

[0085] The polymer material is composed of cellulose acetate and chitosan with a mass ratio of 2:1.

[0086] S1, the polymer material is added to a 10% sodium hydroxide aqueous solution, the mass ratio of the polymer material and the sodium hydroxide aqueous solution is 1:10, and stirring is performed at a speed of 200 rpm until complete dissolution to obtain a sol; the sol is subjected to freeze-thaw cycle treatment, is cooled to 0°C at a speed of 2°C / min, is cooled to -20°C at a speed of 1°C / min, is frozen for 6 h; then is warmed to 0°C at a speed of 1°C / min, is warmed to 25°C at a speed of 1.5°C / min, is thawed for 3 h, and the cycle is repeated 4 times; the freeze-thaw treated gel is soaked in deionized water for 1 d, is vacuum dried at 60°C, and a primary gel is obtained.

[0087] Example 14

[0088] Example 14 is based on Example 3, and the only difference between Example 14 and Example 3 is that in Example 14, the polymer material in step S1 further comprises chitosan, and the mass ratio of cellulose acetate and chitosan is 3:1.

[0089] The polymer material is composed of cellulose acetate and chitosan in a mass ratio of 3:1.

[0090] S1, the polymer material is added to a 10% sodium hydroxide aqueous solution, the mass ratio of the polymer material and the sodium hydroxide aqueous solution is 1:10, and stirring is performed at a speed of 200 rpm until complete dissolution to obtain a sol; the sol is subjected to freeze-thaw cycle treatment, is cooled to 0°C at a speed of 2°C / min, is cooled to -20°C at a speed of 1°C / min, is frozen for 6 h; then is warmed to 0°C at a speed of 1°C / min, is warmed to 25°C at a speed of 1.5°C / min, is thawed for 3 h, and the cycle is repeated 4 times; the freeze-thaw treated gel is soaked in deionized water for 1 d, is vacuum dried at 60°C, and a primary gel is obtained.

[0091] Example 15

[0092] Example 15 is based on Example 3, and the only difference between Example 15 and Example 3 is that in Example 15, the polymer material in step S1 further comprises chitosan, and the mass ratio of cellulose acetate and chitosan is 2.5:1.

[0093] The polymer material is composed of cellulose acetate and chitosan in a mass ratio of 2.5:1.

[0094] S1, the polymer material is added to a 10% sodium hydroxide aqueous solution, the mass ratio of the polymer material and the sodium hydroxide aqueous solution is 1:10, and stirring is performed at a speed of 200 rpm until complete dissolution to obtain a sol; the sol is subjected to freeze-thaw cycle treatment, is cooled to 0°C at a speed of 2°C / min, is cooled to -20°C at a speed of 1°C / min, is frozen for 6 h; then is warmed to 0°C at a speed of 1°C / min, is warmed to 25°C at a speed of 1.5°C / min, is thawed for 3 h, and the cycle is repeated 4 times; the freeze-thaw treated gel is soaked in deionized water for 1 d, and is vacuum dried at 60°C to obtain a primary gel.

[0095] Example 16

[0096] Example 16 is based on Example 13, and the difference between Example 16 and Example 13 is that the polymer material in Example 16 is composed of cellulose acetate and chitosan with a mass ratio of 1:1.

[0097] Example 17

[0098] Example 17 is based on Example 13, and the difference between Example 17 and Example 13 is that the polymer material in Example 17 is composed of cellulose acetate and chitosan with a mass ratio of 4:1.

[0099] Example 18

[0100] Example 18 is based on Example 13, and the difference between Example 18 and Example 13 is that the chitosan in Example 18 is modified, and is prepared by the following steps:

[0101] The chitosan is dissolved in an acetic acid solution with a volume concentration of 1% to prepare a chitosan solution with a mass concentration of 2%; a 2,3-epoxypropyltrimethylammonium chloride aqueous solution with a concentration of 2 mol / L is added to the chitosan solution, the molar ratio of chitosan and 2,3-epoxypropyltrimethylammonium chloride is 1:1.9, the pH is adjusted to 9, and stirring is performed at a speed of 500 rpm under the condition of a 70°C water bath for 4 h; after the reaction is completed, anhydrous ethanol is added for alcohol precipitation, centrifugation is performed to obtain a precipitate, the precipitate is washed with 80% ethanol, dialysis is performed in deionized water using a 3500 Da dialysis bag, and after dialysis at 4°C for 48 h, vacuum drying is performed at 60°C to obtain quaternary ammonium chitosan.

[0102] Comparative Example 1

[0103] Comparative Example 1 is based on Example 3, and the difference between Comparative Example 1 and Example 3 is that no covalent organic framework material is added in the crosslinking reaction in step S2 of Comparative Example 1.

[0104] The polymer material is cellulose acetate.

[0105] S1, the polymer material is added to a 10% sodium hydroxide aqueous solution, the mass ratio of the polymer material and the sodium hydroxide aqueous solution is 1:10, stirring at a speed of 200 rpm until completely dissolved to obtain a sol; the sol is subjected to freeze-thaw cycle treatment, cooled to 0℃ at a rate of 2℃ / min, cooled to -20℃ at a rate of 1℃ / min, frozen for 6h; then warmed to 0℃ at a rate of 1℃ / min, and warmed to 25℃ at a rate of 1.5℃ / min, thawed for 3h, and the cycle is repeated 4 times; the freeze-thaw treated gel is soaked in deionized water for 1d, and vacuum dried at 60℃ to obtain a primary gel;

[0106] S2, the mass ratio of the primary gel and sodium silicate is 1:0.25; the sodium silicate is dissolved in deionized water to prepare a 0.5mol / L solution, the pH is adjusted to 4.5 using dilute sulfuric acid, and the solution is stirred at 200 rpm at 80℃ for 2h to obtain an aerogel precursor; the primary gel is immersed in the aerogel precursor solution, and the intermittent oscillation reaction is carried out at 50℃ for 7h (oscillation frequency 30 rpm, oscillation for 5min every 30min) to obtain a preliminary crosslinked gel;

[0107] S3, lithium chloride is dissolved in DMF, and polyacrylonitrile is added to prepare a spinning solution with a mass concentration of 10% polyacrylonitrile + 2% lithium chloride, the voltage is 16.5kV, the injection speed is 1.25mL / h, the receiving distance is 17.5cm, and the environmental humidity is less than 40%, electrospinning is carried out, then the fibers are soaked in ethanol for 12h, and vacuum dried at 60℃ to obtain a fiber template; the preliminary crosslinked gel is cut into 2mm slices, laid on the surface of the fiber template, and pressed at 0.2MPa for 3h to obtain a gel template composite; the gel template composite is immersed in a 1, 3, 5-triformylbenzene solution (0.2mol / L, solvent is a mixed solvent of ethanol and acetic acid with a volume ratio of 10:1), and reacted at 80℃ for 12h to obtain a semi-finished product;

[0108] S4, the semi-finished product is sequentially soaked in water, ethanol and tert-butanol, each solvent is replaced for 3 times, and each soaking time is 2h, after replacement, the semi-finished product is immersed in a 5% hexadecyltrimethoxysilane ethanol solution, acetic acid is used to adjust the pH to 5, and the reaction is carried out at 60℃ for 8h, the semi-finished product is washed with n-hexane for 3 times, and vacuum dried at 60℃ for 2h to obtain a modified semi-finished product;

[0109] S5, the modified semi-finished product is subjected to gradient temperature constant pressure drying, the modified semi-finished product is placed in a constant pressure drying oven, incubated at 40℃ for 2h, incubated at 60℃ for 4h, and incubated at 80℃ until the weight is constant, the heating rate is 1.5℃ / min, and an aerogel cloud fiber is obtained.

[0110] Performance detection experiment

[0111] (1) Density detection: The mass and volume of the test sample were tested, and the density was calculated. Each sample was tested three times, and the average value was taken after measurement. The results are recorded in Table 1.

[0112] (2) Porosity detection: The porosity was calculated by gas adsorption method and mercury injection method. Each sample was tested three times, and the average value was taken after measurement. The results are recorded in Table 1.

[0113] (3) Thermal conductivity detection: The thermal conductivity of the sample was tested by steady-state heat flow meter method. Each sample was tested three times, and the average value was taken after measurement. The results are recorded in Table 1.

[0114] Table 1: Detection results of lightweight, loftiness and thermal insulation performance of cloud wool fibers

[0115] Detection result Density (g / cm 2 ) Porosity (%) Thermal conductivity (W / m·K) Example 1 0.023 92.8 0.025 Example 2 0.021 93.3 0.024 Example 3 0.020 93.6 0.022 Example 4 0.025 90.5 0.028 Example 5 0.019 93.7 0.022 Example 6 0.025 89.6 0.030 Example 7 0.022 92.5 0.025 Example 8 0.024 91.2 0.026 Example 9 0.023 90.8 0.028 Example 10 0.026 88.7 0.031 Example 11 0.029 86.5 0.033 Example 12 0.024 92.1 0.029 Example 13 0.018 94.2 0.021 Example 14 0.019 94.0 0.022 Example 15 0.017 94.9 0.020 Example 16 0.021 93.8 0.023 Example 17 0.020 93.9 0.022 Example 18 0.016 96.3 0.017 Comparative Example 1 0.035 82.2 0.045

[0116] From Table 1, it can be seen that the density of Examples 1-3 is less than 0.023 g / cm 2 , the porosity is greater than 92.8%, and the thermal conductivity is less than 0.025 W / m·K, so it can be seen that the cloud wool fibers prepared by the present application have good lightweight, high loftiness and good thermal insulation performance.

[0117] From Table 1, it can be seen that the difference between Examples 4, 5 and Example 3 is only that the number of freeze-thaw cycle treatments in Example 4 is 1 time, and the number of freeze-thaw cycle treatments in Example 5 is 6 times. Compared with Examples 4, 5 and Example 3, the performance decreases; this is because reducing the number of freeze-thaw cycles affects the pore structure of the gel, and the performance decreases; increasing the number of freeze-thaw cycles has limited effect on the improvement of porosity, but increases the brittleness of the gel skeleton structure, affecting the performance of the cloud wool fibers.

[0118] From Table 1, it can be seen that the difference between Examples 6, 7 and Example 3 is only that the mass ratio of primary gel, sodium silicate and covalent organic framework material in Example 6 is 1:0.25:0.002, and the mass ratio of primary gel, sodium silicate and covalent organic framework material in Example 7 is 1:0.25:0.02. Compared with Examples 6, 7 and Example 3, the performance decreases; this is because changing the proportion of gel crosslinking modification substances, too much or too little covalent organic framework material will affect the proportion and stability of the pore structure, thus affecting the performance.

[0119] From Table 1, it can be seen that the difference between Examples 8, 9 and Example 3 is only that the reaction conditions of the preliminary crosslinking gel reaction are changed in Examples 8, 9. Compared with Examples 8, 9 and Example 3, the performance decreases; this is because the reaction conditions will affect the uniformity of the crosslinking reaction, thus affecting the connectivity of the pores, and the performance of the fibers is affected.

[0120] From Table 1, it can be seen that the difference between Example 10 and Example 3 is only that the secondary cross-linking gel in Example 10 does not undergo a stepwise temperature reaction, and the performance of Example 10 is lower than that of Example 3; this is because the absence of a stepwise reaction can cause the pore structure to collapse and the pore connectivity to decrease, thereby causing the performance to decrease.

[0121] From Table 1, it can be seen that the difference between Examples 11 and 12 and Example 3 is only that no lithium chloride is added to the spinning solution in Example 11, and 5% lithium chloride is added to the spinning solution in Example 12; the performance of Examples 11 and 12 is lower than that of Example 3; this is because the absence of lithium chloride can cause the electrospun fiber diameter to increase and the porosity to decrease significantly; and too high a concentration of lithium chloride can cause residues to occur in the fiber, thereby affecting the fiber density and thermal insulation performance.

[0122] From Table 1, it can be seen that the difference between Examples 13-18 and Example 3 is only that chitosan is compounded with cellulose acetate within a limited range in Examples 13-15, the uniformity of the pore distribution is improved by enhancing cross-linking, and the performance is improved; the performance of Examples 16 and 17 is decreased because the limited ratio is destroyed; and the performance of Example 18 is further improved because the chitosan is subjected to quaternary ammonium modification treatment on the basis of Example 15, thereby enhancing the hydrophilicity and cross-linking density and improving the stability of the pore structure.

[0123] From Table 1, it can be seen that the difference between Comparative Example 1 and Example 3 is only that no covalent organic framework material is added in Comparative Example 1, and the performance of Comparative Example 1 is significantly lower than that of Example 3; this is because the pore structure is single and easy to collapse by using sodium silicate for cross-linking reaction, and therefore the performance is significantly decreased.

[0124] The specific embodiments are only an explanation of the present application, and are not a limitation of the present application, and through the above description, relevant personnel can make various changes and modifications without deviating from the technical idea of the present application. The technical scope of the present application is not limited to the content of the specification, and must be determined by the scope of the claims.

Claims

1. A process for increasing the loft of a cloud-wool fiber, characterized by: It comprises the following steps: S1, dissolving the polymer material in a solvent to obtain a sol, treating by freeze-thaw cycle, soaking and drying to obtain a primary gel; the polymer material comprises cellulose acetate; S2, dissolving sodium silicate in a solvent, adjusting the pH to be acidic, heating and stirring to obtain an aerogel precursor; immersing the primary gel in the aerogel precursor solution, heating and stirring to obtain a preliminary crosslinked gel; Mixing the covalent organic framework material suspension and the preliminary crosslinked gel, heating and stirring to obtain a secondary crosslinked gel; S3, electrospinning the polyacrylonitrile spinning solution, soaking and drying to obtain a fiber template; placing the secondary crosslinked gel on the fiber template, pressurizing to obtain a gel template composite; immersing the gel template composite in a 1,3,5-triformylbenzene solution, heating and reacting to obtain a semi-finished product; S4, performing gradient solvent replacement on the semi-finished product, immersing in a hexadecyltrimethoxysilane solution after replacement, heating and reacting, washing and drying to obtain a modified semi-finished product; S5, using gradient temperature increase normal pressure drying to modify the semi-finished product to obtain aerogel cloud wool fibers.

2. A method of increasing the loft of a cloud-wool fiber according to claim 1, characterized in that: The freeze-thaw cycle treatment in the S1 step is at -20-25℃ for 3-5 times, cooling at a rate of 1.5-2.5℃ / min to 0℃, cooling at a rate of 0.5-1.5℃ / min to -20℃, freezing for 4-8h, heating at a rate of 0.5-1.5℃ / min to 0℃, heating at a rate of 1-2℃ / min to 25℃, and thawing for 2-4h.

3. The method of claim 1, wherein the method is characterized by: The polymer material further comprises chitosan.

4. The method of claim 3, wherein the method is characterized by: The mass ratio of cellulose acetate and chitosan in the polymer material is (2-3):

1.

5. A method of increasing the loft of a cloud-wool fiber according to claim 4, characterized in that: The chitosan is modified and prepared by the following steps: Adding 2,3-epoxypropyltrimethylammonium chloride solution to the chitosan solution, adjusting the pH to be alkaline, heating and stirring in a water bath, alcohol precipitation after the reaction is completed, centrifugation, washing, dialysis and drying to obtain quaternized chitosan.

6. The method for preparing cloud-like fibers with improved bulkiness according to claim 1, characterized in that: The mass ratio of the primary gel, sodium silicate and covalent organic framework material in the step S2 is 1:0.25:(0.005-0.015).

7. The method for preparing cloud-like fibers with improved bulkiness according to claim 1, characterized in that: The reaction conditions of the preliminary crosslinked gel in the step S2 are 40-60℃ for 6-8h, intermittent oscillation reaction.

8. The method for preparing cloud-like fibers with improved bulkiness according to claim 1, characterized in that: The reaction conditions of the secondary crosslinked gel in the step S2 are mixing the covalent organic framework material suspension into the preliminary crosslinked gel, adding urea as a dynamic crosslinking agent, stirring at 30-50℃ for 3-5h, heating at a rate of 1.5-2.5℃ / min to 75-85℃, and reacting for 6-8h.

9. The method for preparing cloud-like fibers with improved bulkiness according to claim 1, characterized in that: The polyacrylonitrile spinning solution in the step S3 contains lithium chloride with a mass fraction of 1-3%.

10. A method of increasing the loft of a cloud-wool fiber according to claim 9, characterized in that: The electrospinning conditions in the step S3 are voltage 15-18kV, injection speed 1-1.5mL / h, and receiving distance 15-20cm.