Preparation method of aerogel heat-insulating and warm-keeping fiber

Abstract

The invention discloses a preparation method of aerogel heat-insulating and warm-keeping fibers, and relates to the technical field of high polymer materials. The preparation method comprises the following steps: breaking hydrogen bonds among microcrystalline cellulose molecules by using an ionic solvent, exposing more active sites, connecting nano SiO2, nano Al2O3 and nano TiO2, grafting dopamine, polymerizing to form polydopamine particles, and preparing aerogel with different microscales and a three-dimensional network porous structure. Cavities with different sizes are provided for storing still air, the thermal insulation performance of the aerogel is improved by utilizing the small-size effect and quantum confinement effect of nanoparticles, and meanwhile, the aerogel also has relatively good mechanical strength, so that the mechanical reinforcing property is improved. And secondly, by adding tetraethoxysilane, methyltrimethoxysilane and gamma-glycidyl ether oxypropyl trimethoxysilane, the binding force between the aerogel and the fiber precursor is improved, and the strength and flexibility of the fiber are improved. The fiber prepared by the invention has the effects of heat insulation and excellent mechanical properties.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer materials, in particular to a method for preparing aerogel heat-insulating and warm-keeping fibers. Background Art

[0002] Aerogel, a new lightweight solid material with a nanoporous network structure, is widely used in thermal insulation due to its extremely low thermal conductivity. Aerogel fiber, a new thermal insulation material, has garnered significant attention in recent years. Its excellent thermal insulation properties and lightweight properties have led to its widespread use in clothing, home furnishings, outdoor equipment, and other fields.

[0003] However, despite the many advantages of aerogel fibers, they still face some problems and challenges in practical applications. Aerogels have problems such as high brittleness and low strength in practical applications, which limit their application in the fiber field. Therefore, the development of an aerogel thermal insulation fiber with excellent thermal insulation performance and a simple preparation process has important practical application value. The thermal insulation and heat insulation properties of aerogel fibers mainly rely on nanomaterials, such as carbon nanotubes and graphene. These nanomaterials have poor stability and are prone to reactions such as agglomeration and oxidation under high temperature or chemical conditions, which affect the performance of the fiber. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for preparing aerogel thermal insulation fiber to solve the problems existing in the prior art.

[0005] In order to solve the above technical problems, the present invention provides the following technical solution: a method for preparing aerogel thermal insulation fiber, comprising the following preparation steps: (1) Heat a dilute sulfuric acid solution to 45-65°C, add 50-150g of microcrystalline cellulose per liter of dilute sulfuric acid solution, add microcrystalline cellulose to the stirred dilute sulfuric acid solution at a stirring speed of 120rpm, keep the temperature for 60min, heat the hydrochloric acid solution to 100-120°C, keep the temperature for 90min, filter and remove the hydrolysis reaction liquid to obtain a hydrolysis solid product; wash the hydrolysis solid product with deionized water three times, and then dry to obtain activated microcrystalline cellulose; mix 1-vinyl-3-alkylimidazole bromide and 1-methyl-3-methylimidazole chloride in a weight ratio of 1:1-2 to form an ionic solvent, heat the ionic solvent to 800-950°C, stir at a constant speed of 120rpm, and then gradually add the activated microcrystalline cellulose to the ionic solvent during the stirring process until the ionic solvent is completely clear to obtain a clear microcrystalline cellulose solution; (2) Add nano-SiO2, nano-Al2O3 and nano-TiO2 in a mass ratio of 2:1:1 to a clarified microcrystalline cellulose solution, and then stir and homogenize at a stirring speed of 240 rpm for 20 minutes to obtain a suspension; add anhydrous ethanol to the obtained suspension and cool it to 20°C, then let it stand and filter it in turn, take the solid and add it to the emulsion for ultrasonic dispersion for 1.5 hours, the ultrasonic frequency is 20-40 kHz, and the time is 30-60 minutes. The emulsion is composed of sodium dodecylbenzenesulfonate and polyoxyethylene sorbitan monolaurate in a weight ratio of 1.5:1; then add dopamine monomer to the emulsion and stir at a stirring speed of 60-120 rpm. After stirring for 30 minutes, the suspension is uniformly polymerized at 60°C and irradiated under nitrogen protection for 12-24 hours, and then filtered, washed with deionized water three times, and dried at 50°C to obtain microparticles; (3) Ultrasonic dispersion of 1-3 parts of microparticles in 150 parts of anhydrous ethanol, adding 15-35 parts of ethyl orthosilicate and stirring evenly, stirring at a speed of 60 rpm for 20 minutes, then adding 15 parts of water and continuing stirring for 20 minutes, then adding hydrochloric acid solution to adjust the pH to 3, continuing stirring and hydrolyzing for 3 hours, adding ammonia water to adjust the pH to 9, stirring at 600-800 rpm for 30 minutes to obtain a wet gel; the wet gel was placed in a sealed environment at 45°C for 40 hours, replaced with anhydrous ethanol twice, immersed in a methyltrimethoxysilane solution with a concentration of 2-8 g / L for 15 hours, taken out, immersed in a γ-glycidyloxypropyltrimethoxysilane solution with a concentration of 1-6 g / L for 15 hours, then freeze-dried at -40°C for 6 hours, taken out and dried in a vacuum for 24 hours to obtain a modified silica aerogel; 8-9.6 parts of polypropylene, 0.7- 1.5 parts of propenyltrichlorosilane, 0.001-0.002 parts of a catalyst, and 0.3-0.9 parts of a modified silica aerogel are put into a high-speed stirrer, stirred at a low speed of 60-120 rpm for 10 minutes, and then stirred at a high speed of 600-800 rpm for 30 minutes. The stirring temperature is controlled at 100°C to ensure that the various raw materials are uniformly mixed. The mixture is then put into a reactive twin-screw extruder at a screw extrusion temperature of 200-230°C. After melt mixing, the mixture is extruded, stretched, and pelletized to obtain blended particles. The blended particles are then put into a spinning screw extruder. The molten material enters a "C"-shaped spinneret through a spinneret assembly and is extruded into melt fibers. The fibers are then cooled by cooling air at a temperature of 30°C, stretched by a hot roller at a temperature of 50-90°C, and finally wound on a winder at a winding speed of 2500 m / min to obtain modified polypropylene fibers.

[0006] Furthermore, the concentration of dilute sulfuric acid in step (1) is 0.2-1.4 mol / L.

[0007] Furthermore, in step (1), the particle size of the microcrystalline cellulose is 50-350 μm.

[0008] Furthermore, the amount of microcrystalline cellulose used in step (1) is 0.045-0.065 times the mass of the ionic solvent.

[0009] Furthermore, the solid-liquid ratio in step (2) is 1:20-45.

[0010] Furthermore, in step (2), the mass ratio of the suspension to anhydrous ethanol is 3:1-2.

[0011] Furthermore, in step (2), the mass ratio of dopamine monomer to microcrystalline cellulose is 1:0.5-1.5.

[0012] Furthermore, the concentration of the hydrochloric acid solution in step (3) is 1 mol / L.

[0013] Furthermore, the vacuum degree in step (3) is -0.085 MPa.

[0014] Furthermore, the stretching ratio in step (3) is 1.4-2.4.

[0015] Compared with the prior art, the present invention has the following beneficial effects: The present invention combines nanoparticles, microcrystalline cellulose, and dopamine-modified aerogel to prepare fibers through melt spinning, thereby achieving the effects of thermal insulation and excellent mechanical properties.

[0016] First, the present invention improves the thermal insulation performance of aerogel by compounding nano-SiO2, nano-Al2O3 and nano-TiO2, and utilizing the small size effect and quantum confinement effect of nanoparticles; uses the anions and cations of the ionic solvent to interact with the hydrogen atoms and oxygen atoms in the hydroxyl groups of microcrystalline cellulose, destroying the hydrogen bonds between the microcrystalline cellulose molecules, so that the microcrystalline cellulose exposes more active sites; then uses the activated microcrystalline cellulose to connect the nanoparticles, and then grafts dopamine to form polydopamine particles through polymerization to modify the aerogel, thereby preparing aerogels with three-dimensional network porous structures of different microscopic scales, providing cavities of different sizes for storing still air, and further improving the thermal insulation performance of the aerogel; and the staggered points present effective bonding and interconnection, which can have good mechanical strength, thereby combining the microcrystalline cellulose, aerogel and nanoparticles to improve mechanical reinforcement; Secondly, by adding tetraethyl orthosilicate, methyltrimethoxysilane and γ-glycidyloxypropyltrimethoxysilane, the bonding force between the aerogel and the fiber precursor is improved, and the strength and flexibility of the fiber are improved; the present invention prepares aerogel thermal insulation and thermal insulation fiber through a melt spinning process, the process flow is simple, the cost is low, and it is suitable for large-scale industrial production; the aerogel thermal insulation and thermal insulation fiber prepared by the present invention has excellent thermal insulation and thermal insulation properties, and has broad application prospects in the fields of aerospace, national defense and military industry, building energy conservation, etc. DETAILED DESCRIPTION

[0017] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0018] In order to more clearly illustrate the method provided by the present invention, the following examples are used to describe in detail the various index testing methods of an aerogel thermal insulation fiber prepared in the following examples. Warmth retention: The antibacterial properties of the examples and comparative examples were tested for warmth retention in accordance with GB / T11048-2008-T “Textiles for physiological comfort - Determination of thermal and moisture resistance under steady-state conditions”.

[0019] Strength: The antibacterial properties of the examples and comparative examples were tested for breaking strength according to the national standard GB / T 3923.1-1997, “Textile fabrics - Tensile properties - Determination of breaking strength and elongation at break - Strip method”.

[0020] Example 1; (1) A dilute sulfuric acid solution is heated to 45°C, 50 g of microcrystalline cellulose is added per liter of dilute sulfuric acid solution, microcrystalline cellulose is added to the dilute sulfuric acid solution under stirring, the stirring speed is 120 rpm, and the reaction is kept warm for 60 minutes. The hydrochloric acid solution is heated to 100°C, and the reaction is kept warm for 90 minutes. The hydrolysis reaction liquid is filtered to remove the hydrolysis reaction liquid to obtain a hydrolysis solid product; the hydrolysis solid product is washed three times with deionized water and then dried to obtain activated microcrystalline cellulose; 1-vinyl-3-alkylimidazole bromide and 1-methyl-3-methylimidazole chloride are mixed in a weight ratio of 1:1 to form an ionic solvent, the ionic solvent is heated to 800°C, and stirred at a constant speed of 120 rpm. Then, during the stirring process, the activated microcrystalline cellulose is gradually added to the ionic solvent, the amount of microcrystalline cellulose is 4.5 wt% of the ionic solvent, and the ionic solvent is completely clear to obtain a clear microcrystalline cellulose solution; (2) Add nano-SiO2, nano-Al2O3 and nano-TiO2 in a mass ratio of 2:1:1 to the clarified microcrystalline cellulose solution, with a solid-liquid ratio of 1:20, and then stir and homogenize at a stirring speed of 240 rpm for 20 min to obtain a suspension; add anhydrous ethanol to the obtained suspension and cool it to 20°C, with a mass ratio of the suspension to anhydrous ethanol of 3:1, and then let it stand and filter in sequence. Take the solid and add it to the emulsion for ultrasonic dispersion for 1.5 h at an ultrasonic frequency of 20 kHz, time is 30 minutes, the emulsion is composed of sodium dodecylbenzenesulfonate and polyoxyethylene sorbitan monolaurate in a weight ratio of 1.5:1; then dopamine monomer is added to the emulsion and stirred at a stirring speed of 60 rpm, the mass ratio of dopamine monomer to microcrystalline cellulose is 1:0.5, and after stirring for 30 minutes, the polymerization reaction is carried out at 60°C and irradiation conditions for 12 hours under nitrogen protection, and then filtered, washed with deionized water three times, and dried at 50°C to obtain microparticles; (3) Ultrasonic dispersion of 1 part of microparticles in 150 parts of anhydrous ethanol, adding 15 parts of ethyl orthosilicate and stirring evenly, stirring at a speed of 60 rpm for 20 minutes, then adding 15 parts of water and continuing stirring for 20 minutes, then adding 1 mol / L hydrochloric acid solution to adjust the pH to 3, continuing stirring and hydrolyzing for 3 hours, adding ammonia water to adjust the pH to 9, stirring at 600 rpm for 30 minutes to obtain a wet gel; the wet gel was placed in a sealed environment at 45°C for 40 hours, replaced with anhydrous ethanol twice, immersed in a methyltrimethoxysilane solution with a concentration of 2 g / L for 15 hours, taken out, immersed in a γ-glycidyloxypropyltrimethoxysilane solution with a concentration of 1 g / L for 15 hours, then freeze-dried at -40°C for 6 hours, taken out and dried in a vacuum for 24 hours, the vacuum degree was -0.085 MPa, and a modified silica aerogel was obtained. 8 parts of polypropylene, 0.7 parts of propylene trichlorosilane, 0.001 parts of catalyst, and 0.3 parts of modified silica aerogel are put into a high-speed stirrer, first stirred at a low speed of 60 rpm for 10 minutes, then stirred at a high speed of 600 rpm for 30 minutes, and the stirring temperature is controlled to be always at 100°C to ensure that the various raw materials are uniformly mixed. Then, the raw materials are put into a reactive twin-screw extruder with a screw extrusion temperature of 200°C. After melt mixing, the raw materials are extruded, stretched, and pelletized to obtain blended particles. Then, the blended particles are put into a spinning screw extruder. The molten material enters a "C"-type spinneret through a spinneret assembly and is extruded into melt fibers. The fibers are then cooled by cooling air at a temperature of 30°C, and then stretched by a hot roller at 50°C with a stretching ratio of 1.4. Finally, the fibers are wound on a winder at a winding speed of 2500 m / min to obtain modified polypropylene fibers.

[0021] Example 2; (1) A dilute sulfuric acid solution is heated to 55°C, 100 g of microcrystalline cellulose is added per liter of dilute sulfuric acid solution, microcrystalline cellulose is added to the dilute sulfuric acid solution under stirring, the stirring speed is 120 rpm, and the reaction is kept warm for 60 minutes, then the hydrochloric acid solution is heated to 110°C, and the reaction is kept warm for 90 minutes, and the hydrolysis reaction liquid is filtered to remove the hydrolysis reaction liquid to obtain a hydrolysis solid product; the hydrolysis solid product is washed three times with deionized water, and then dried to obtain activated microcrystalline cellulose; 1-vinyl-3-alkylimidazole bromide and 1-methyl-3-methylimidazole chloride are mixed in a weight ratio of 1:1.5 to form an ionic solvent, the ionic solvent is heated to 875°C, and stirred at a constant speed of 120 rpm, and then the activated microcrystalline cellulose is gradually added to the ionic solvent during the stirring process, the amount of microcrystalline cellulose is 5.5 wt% of the ionic solvent, until the ionic solvent is completely clear, and a clear microcrystalline cellulose solution is obtained; (2) Mix nano-SiO2, nano-Al2O3 and nano-TiO2 in a mass ratio of 2:1:1 The suspension was added to the clarified microcrystalline cellulose solution at a solid-liquid ratio of 1:37.5, and then stirred homogenously at a stirring speed of 240 rpm for 20 minutes to obtain a suspension; anhydrous ethanol was added to the obtained suspension and cooled to 20°C, the mass ratio of the suspension to anhydrous ethanol was 3:1.5, and then the suspension was allowed to stand and filtered in sequence, and the solid was added to the emulsion for ultrasonic dispersion for 1.5 hours at an ultrasonic frequency of 30 kHz for 45 minutes. The emulsion consisted of sodium dodecylbenzenesulfonate and polyoxyethylene sorbitan monolaurate in a weight ratio of 1.5:1; dopamine monomer was then added to the emulsion and stirred at a stirring speed of 80 rpm. The mass ratio of dopamine monomer to microcrystalline cellulose was 1:1. After stirring for 30 minutes, the suspension was subjected to polymerization reaction at 60°C and irradiation conditions for 18 hours under nitrogen protection, and then filtered, washed with deionized water three times, and dried at 50°C to obtain microparticles; (3) Ultrasonic dispersion of 2 parts of microparticles in 150 parts of anhydrous ethanol, adding 25 parts of ethyl orthosilicate and stirring evenly, stirring at a speed of 60 rpm for 20 minutes, then adding 15 parts of water and continuing stirring for 20 minutes, then adding 1 mol / L hydrochloric acid solution to adjust the pH to 3, continuing stirring and hydrolyzing for 3 hours, adding ammonia water to adjust the pH to 9, stirring at 700 rpm for 30 minutes to obtain a wet gel; the wet gel was placed in a sealed environment at 45°C for 40 hours, replaced with anhydrous ethanol twice, immersed in a 5 g / L methyltrimethoxysilane solution for 15 hours, taken out, immersed in a 3.5 g / L γ-glycidyloxypropyltrimethoxysilane solution for 15 hours, then freeze-dried at -40°C for 6 hours, taken out and dried in a vacuum for 24 hours, the vacuum degree was -0.085 MPa, and a modified silica aerogel was obtained. 8.8 parts of polypropylene, 1.1 parts of propylene trichlorosilane, 0.0015 parts of a catalyst, and 0.6 parts of modified silica aerogel were put into a high-speed stirrer, first stirred at a low speed of 80 rpm for 10 minutes, then stirred at a high speed of 700 rpm for 30 minutes, and the stirring temperature was controlled to be always at 100°C to ensure that the various raw materials were uniformly mixed. Then, the mixture was put into a reactive twin-screw extruder with a screw extrusion temperature of 215°C. After melt mixing, the mixture was extruded, stretched, and pelletized to obtain blended particles. Then, the blended particles were put into a spinning screw extruder. The molten material entered a "C"-type spinneret through a spinneret assembly and was extruded into melt fibers. The fibers were then cooled by cooling air at a temperature of 30°C, and then stretched by a hot roller at 70°C with a stretch ratio of 1.9. Finally, the fibers were wound on a winder at a winding speed of 2500 m / min to obtain modified polypropylene fibers.

[0022] Example 3; (1) A dilute sulfuric acid solution was heated to 65°C, 150 g of microcrystalline cellulose was added per liter of dilute sulfuric acid solution, microcrystalline cellulose was added to the dilute sulfuric acid solution under stirring, the stirring speed was 120 rpm, and the reaction was kept warm for 60 minutes, then the hydrochloric acid solution was heated to 120°C, and the reaction was kept warm for 90 minutes, and the hydrolysis reaction liquid was filtered to remove the hydrolysis reaction liquid to obtain a hydrolysis solid product; the hydrolysis solid product was washed three times with deionized water, and then dried to obtain activated microcrystalline cellulose; 1-vinyl-3-alkylimidazole bromide and 1-methyl-3-methylimidazole chloride were mixed in a weight ratio of 1:2 to form an ionic solvent, the ionic solvent was heated to 950°C, and stirred at a constant speed of 120 rpm, and then the activated microcrystalline cellulose was gradually added to the ionic solvent during the stirring process, the amount of microcrystalline cellulose was 6.5 wt% of the ionic solvent, until the ionic solvent was completely clear, and a clear microcrystalline cellulose solution was obtained; (2) Add nano-SiO2, nano-Al2O3 and nano-TiO2 in a mass ratio of 2:1:1 to the clarified microcrystalline cellulose solution, with a solid-liquid ratio of 1:45, and then stir and homogenize at a stirring speed of 240 rpm for 20 min to obtain a suspension; add anhydrous ethanol to the obtained suspension and cool it to 20°C, with a mass ratio of the suspension to anhydrous ethanol of 3:2, and then let it stand and filter in sequence. Take the solid and add it to the emulsion for ultrasonic dispersion for 1.5 h at an ultrasonic frequency of 40 kHz, the time is 60 minutes, the emulsion is composed of sodium dodecylbenzenesulfonate and polyoxyethylene sorbitan monolaurate in a weight ratio of 1.5:1; then dopamine monomer is added to the emulsion and stirred at a stirring speed of 120 rpm, the mass ratio of dopamine monomer to microcrystalline cellulose is 1:1.5, and after stirring for 30 minutes, the polymerization reaction is carried out at 60°C and irradiation conditions under nitrogen protection for 24 hours, and then filtered, washed with deionized water three times, and dried at 50°C to obtain microparticles; (3) Ultrasonic dispersion of 3 parts of microparticles in 150 parts of anhydrous ethanol, adding 35 parts of ethyl orthosilicate and stirring evenly at a stirring speed of 60 rpm for 20 min, then adding 15 parts of water and continuing stirring for 20 min, then adding 1 mol / L hydrochloric acid solution to adjust the pH to 3, continuing stirring and hydrolyzing for 3 h, adding ammonia water to adjust the pH to 9, stirring at 800 rpm for 30 min to obtain a wet gel; the wet gel was placed in a sealed environment at 45 ° C for 40 hours, replaced with anhydrous ethanol twice, immersed in a methyltrimethoxysilane solution with a concentration of 8 g / L for 15 hours, taken out, immersed in a γ-glycidyloxypropyltrimethoxysilane solution with a concentration of 6 g / L for 15 hours, then freeze-dried at -40 ° C for 6 hours, taken out and dried in a vacuum for 24 hours, the vacuum degree was -0.085 MPa, and a modified silica aerogel was obtained; 9.6 parts of polypropylene, 1.5 parts of propylene trichlorosilane, 0.002 parts of catalyst, and 0.9 parts of modified silica aerogel were put into a high-speed stirrer, first stirred at a low speed of 120 rpm for 10 minutes, then stirred at a high speed of 800 rpm for 30 minutes, and the stirring temperature was controlled to be always at 100°C to uniformly mix the various raw materials. Then, the mixture was put into a reactive twin-screw extruder with a screw extrusion temperature of 230°C. After melt mixing, the mixture was extruded, stretched, and pelletized to obtain blended particles. Then, the blended particles were put into a spinning screw extruder. The molten material entered a "C"-type spinneret through a spinneret assembly and was extruded into melt fibers. The fibers were then cooled by cooling air at a temperature of 30°C, and then stretched by a hot roller at 90°C with a stretching ratio of 2.4. Finally, the fibers were wound on a winder at a winding speed of 2500 m / min to obtain modified polypropylene fibers.

[0023] Comparative Example 1; The difference between Comparative Example 1 and Example 2 lies in the difference in step (2), whereby step (2) is modified as follows: adding anhydrous ethanol to the clarified microcrystalline cellulose solution and cooling it to 20°C, wherein the mass ratio of the clarified microcrystalline cellulose solution to the anhydrous ethanol is 3:1.5, and then the mixture is allowed to stand and filtered in sequence, and the solid is added to the emulsion for ultrasonic dispersion for 1.5 hours, wherein the ultrasonic frequency is 30 kHz and the time is 45 minutes, and the emulsion is composed of sodium dodecylbenzenesulfonate and polyoxyethylene sorbitan monolaurate in a weight ratio of 1.5:1; then adding dopamine monomer to the emulsion and stirring the mixture, wherein the stirring speed is 80 rpm, and the mass ratio of the dopamine monomer to the microcrystalline cellulose is 1:1, and stirring the mixture for 30 minutes to obtain a uniform mixture, and then carrying out polymerization reaction at 60°C and irradiation conditions for 18 hours under the protection of nitrogen, and then filtering, washing with deionized water three times, and drying at 50°C to obtain microparticles; the remaining steps are the same as those in Example 2.

[0024] Comparative Example 2; The difference between Comparative Example 2 and Example 2 is that there is no step (1), and step (2) is changed to: nano-SiO2, nano-Al2O3 and nano-TiO2 are added to deionized water in a mass ratio of 2:1:1, with a solid-liquid ratio of 1:37.5, and then stirred homogenously at a stirring speed of 240 rpm for 20 min to obtain a suspension; anhydrous ethanol is added to the obtained suspension and cooled to 20 ° C. The mass ratio of the suspension to anhydrous ethanol is 3:1.5, and then the suspension is allowed to stand and filtered in sequence. The solid is added to the emulsion for ultrasonic dispersion for 1.5 h at an ultrasonic frequency of 30 kHz, time is 45 minutes, the emulsion is composed of sodium dodecylbenzenesulfonate and polyoxyethylene sorbitan monolaurate in a weight ratio of 1.5:1; then dopamine monomer is added to the emulsion and stirred at a stirring speed of 80 rpm, the mass ratio of dopamine monomer to microcrystalline cellulose is 1:1, and after stirring for 30 minutes, the polymerization reaction is carried out at 60°C and irradiation conditions under nitrogen protection for 18 hours, and then filtered, washed with deionized water three times, and dried at 50°C to obtain microparticles; the remaining steps are the same as those in Example 2.

[0025] Comparative Example 3; The difference between Comparative Example 3 and Example 2 is that step (2) is different. Step (2) is changed to: nano-SiO2, nano-Al2O3 and nano-TiO2 are added to the clarified microcrystalline cellulose solution in a mass ratio of 2:1:1, with a solid-liquid ratio of 1:37.5, and then stirred and homogenized at a stirring speed of 240 rpm for 20 min to obtain a suspension; anhydrous ethanol is added to the obtained suspension and cooled to 20°C, with a mass ratio of the suspension to anhydrous ethanol of 3:1.5, and then allowed to stand and filtered in sequence, and the solid is added to the emulsion for 1.5 h of ultrasonic dispersion at an ultrasonic frequency of 30 kHz, the time is 45 minutes, the emulsion consists of sodium dodecylbenzenesulfonate and polyoxyethylene sorbitan monolaurate in a weight ratio of 1.5:1, and the polymerization reaction is carried out at 60°C under irradiation conditions for 18 hours, followed by filtration, washing with deionized water three times, and drying at 50°C to obtain microparticles; the remaining steps are the same as those in Example 2.

[0026] Comparative Example 4; The difference between Comparative Example 4 and Example 2 is that step (3) is different. Step (3) is changed to: ultrasonically disperse 2 parts of microparticles into 150 parts of anhydrous ethanol, add 25 parts of ethyl orthosilicate and stir evenly, the stirring speed is 60 rpm, the time is 20 minutes, then add 15 parts of water and continue stirring for 20 minutes, then add 1 mol / L hydrochloric acid solution to adjust the pH to 3, continue stirring and hydrolyze for 3 hours, add ammonia water to adjust the pH to 9, stir at 700 rpm for 30 minutes to obtain a wet gel; the wet gel is placed in a sealed environment at 45°C for aging for 40 hours, replaced with anhydrous ethanol twice, and then freeze-dried at -40°C for 6 hours, taken out and dried in vacuum for 24 hours, the vacuum degree is -0.085 MPa, and a modified silica aerogel is obtained; 8.8 parts of polypropylene, 1.1 parts of propenyltrichlorosilane , 0.0015 parts of catalyst, and 0.6 parts of modified silica aerogel were put into a high-speed stirrer, first stirred at a low speed of 80 rpm for 10 minutes, then stirred at a high speed of 700 rpm for 30 minutes, and the stirring temperature was controlled to be always at 100°C to uniformly mix the various raw materials, and then put into a reactive twin-screw extruder, the screw extrusion temperature was 215°C, after melt mixing, extrusion, drawing, and pelletizing to obtain blended particles; then the blended particles were put into a spinning screw extruder, and the molten material entered the "C" type spinneret through the spinneret assembly to be extruded into melt fibers, and then cooled by cooling air at a wind temperature of 30°C, and then stretched by a hot roller at 70°C with a stretching ratio of 1.9. Finally, the fibers were wound on a winder at a winding speed of 2500 m / min to obtain modified polypropylene fibers; the remaining steps were the same as those in Example 2.

[0027] Effect Examples Table 1 below shows the performance analysis results of an aerogel thermal insulation fiber using Examples 1 to 3 of the present invention and Comparative Examples 1 to 4.

[0028] Table 1

[0029] From the comparison of the experimental data on the thermal insulation of the embodiments and the comparative examples, it can be found that the present invention improves the thermal insulation performance of the aerogel by compounding nano-SiO2, nano-Al2O3 and nano-TiO2, and utilizing the small size effect and quantum confinement effect of nanoparticles; uses the anions and cations of the ionic solvent to interact with the hydrogen atoms and oxygen atoms in the hydroxyl groups of microcrystalline cellulose, destroys the hydrogen bonds between the microcrystalline cellulose molecules, and exposes more active sites of the microcrystalline cellulose, and then uses the activated microcrystalline cellulose to connect the nanoparticles, and then grafts dopamine to form polydopamine particles through polymerization to modify the aerogel, and prepares aerogels with three-dimensional network porous structures of different microscopic scales, providing cavities of different sizes to store still air, and further improving the thermal insulation performance of the aerogel; from the comparison of the experimental data on the breaking strength of the embodiments and the comparative examples, it can be found that the interlaced points of the present invention present effective bonding and interconnection, and can have good mechanical strength, so that the combination of microcrystalline cellulose, aerogel and nanoparticles improves mechanical reinforcement. Secondly, by adding tetraethyl orthosilicate, methyltrimethoxysilane and γ-glycidyloxypropyltrimethoxysilane, the bonding force between the aerogel and the fiber precursor is improved, and the strength and flexibility of the fiber are improved; the present invention prepares aerogel thermal insulation and thermal insulation fiber through a melt spinning process, the process flow is simple, the cost is low, and it is suitable for large-scale industrial production; the aerogel thermal insulation and thermal insulation fiber prepared by the present invention has excellent thermal insulation and thermal insulation properties, and has broad application prospects in the fields of aerospace, national defense and military industry, building energy conservation, etc.

[0030] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the invention can be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the invention is defined by the appended claims, not the foregoing description, and all variations within the meaning and range of equivalents of the claims are intended to be encompassed therein. Any reference in a claim should not be construed as limiting the claim to which it relates.

Claims

1. A method for preparing aerogel thermal insulation fiber, characterized in that: The method comprises the following preparation steps: (1) Heat a dilute sulfuric acid solution to 45-65°C, add 50-150g of microcrystalline cellulose per liter of dilute sulfuric acid solution, add microcrystalline cellulose to the stirred dilute sulfuric acid solution at a stirring speed of 120rpm, keep the temperature for 60min, heat the hydrochloric acid solution to 100-120°C, keep the temperature for 90min, filter and remove the hydrolysis reaction liquid to obtain a hydrolysis solid product; wash the hydrolysis solid product with deionized water three times, and then dry to obtain activated microcrystalline cellulose; mix 1-vinyl-3-alkylimidazole bromide and 1-methyl-3-methylimidazole chloride in a weight ratio of 1:1-2 to form an ionic solvent, heat the ionic solvent to 800-950°C, stir at a constant speed of 120rpm, and then gradually add the activated microcrystalline cellulose to the ionic solvent during the stirring process until the ionic solvent is completely clear to obtain a clear microcrystalline cellulose solution; (2) Add nano-SiO2, nano-Al2O3 and nano-TiO2 in a mass ratio of 2:1:1 to a clarified microcrystalline cellulose solution, and then stir and homogenize at a stirring speed of 240 rpm for 20 minutes to obtain a suspension; add anhydrous ethanol to the obtained suspension and cool it to 20°C, then let it stand and filter it in turn, take the solid and add it to the emulsion for ultrasonic dispersion for 1.5 hours, the ultrasonic frequency is 20-40 kHz, and the time is 30-60 minutes. The emulsion is composed of sodium dodecylbenzenesulfonate and polyoxyethylene sorbitan monolaurate in a weight ratio of 1.5:1; then add dopamine monomer to the emulsion and stir at a stirring speed of 60-120 rpm. After stirring for 30 minutes, the suspension is uniformly polymerized at 60°C and irradiated under nitrogen protection for 12-24 hours, and then filtered, washed with deionized water three times, and dried at 50°C to obtain microparticles; (3) Ultrasonic dispersion of 1-3 parts of microparticles in 150 parts of anhydrous ethanol, adding 15-35 parts of ethyl orthosilicate and stirring evenly, stirring at a speed of 60 rpm for 20 minutes, then adding 15 parts of water and continuing stirring for 20 minutes, then adding hydrochloric acid solution to adjust the pH to 3, continuing stirring and hydrolyzing for 3 hours, adding ammonia water to adjust the pH to 9, stirring at 600-800 rpm for 30 minutes to obtain a wet gel; the wet gel was placed in a sealed environment at 45°C for 40 hours, replaced with anhydrous ethanol twice, immersed in a methyltrimethoxysilane solution with a concentration of 2-8 g / L for 15 hours, taken out, immersed in a γ-glycidyloxypropyltrimethoxysilane solution with a concentration of 1-6 g / L for 15 hours, then freeze-dried at -40°C for 6 hours, taken out and dried in a vacuum for 24 hours to obtain a modified silica aerogel; 8-9.6 parts of polypropylene, 0.7- 1.5 parts of propylene trichlorosilane, 0.001-0.002 parts of a catalyst, and 0.3-0.9 parts of a modified silica aerogel are placed in a high-speed stirrer, stirred at a low speed of 60-120 rpm for 10 minutes, and then stirred at a high speed of 600-800 rpm for 30 minutes. The stirring temperature is controlled at 100°C to ensure uniform mixing of the various raw materials. The mixture is then placed in a reactive twin-screw extruder at a screw extrusion temperature of 200-230°C. After melt mixing, the mixture is extruded, stretched, and pelletized to obtain blended particles. The blended particles are then placed in a spinning screw extruder. The molten material passes through a spinneret assembly and enters a "C"-shaped spinneret to be extruded into melt fibers. The fibers are then cooled by cooling air at a temperature of 30°C, stretched by a hot roller at a temperature of 50-90°C, and finally wound on a winder at a winding speed of 2500 m / min to obtain modified polypropylene fibers.

2. The method for preparing aerogel thermal insulation fiber according to claim 1, characterized in that: The concentration of dilute sulfuric acid in step (1) is 0.2-1.4 mol / L.

3. The method for preparing aerogel thermal insulation fiber according to claim 1, characterized in that: The particle size of the microcrystalline cellulose in step (1) is 50-350 μm.

4. The method for preparing aerogel thermal insulation fiber according to claim 1, characterized in that: The amount of microcrystalline cellulose used in step (1) is 0.045-0.065 times the mass of the ionic solvent.

5. The method for preparing aerogel thermal insulation fiber according to claim 1, characterized in that: The solid-to-liquid ratio in step (2) is 1:20-45.

6. The method for preparing aerogel thermal insulation fiber according to claim 1, characterized in that: The mass ratio of the suspension to anhydrous ethanol in step (2) is 3:1-2.

7. The method for preparing aerogel thermal insulation fiber according to claim 1, characterized in that: In the step (2), the mass ratio of dopamine monomer to microcrystalline cellulose is 1:0.5-1.

5.

8. The method for preparing aerogel thermal insulation fiber according to claim 1, characterized in that: The concentration of the hydrochloric acid solution in step (3) is 1 mol / L.

9. The method for preparing aerogel thermal insulation fiber according to claim 1, characterized in that: The vacuum degree in step (3) is -0.085 MPa.

10. The method for preparing aerogel thermal insulation fiber according to claim 1, characterized in that: The stretching ratio in step (3) is 1.4-2.4.

Images