Viscose aerogel fiber as well as preparation method and application thereof

Abstract

The invention provides a viscose aerogel fiber and a preparation method and application thereof.The viscose aerogel fiber is prepared from viscose and a boric acid ester organosilicon cross-linking agent, the viscose serves as a core raw material, the boric acid ester organosilicon cross-linking agent is introduced in a matched mode, and the viscose aerogel fiber is prepared. The boric acid ester organosilicon cross-linking agent can generate mesoporous organosilicon in situ in the preparation process, so that the heat insulation performance and the mechanical property of the obtained viscose aerogel fiber are improved, and the viscose aerogel fiber has an ultralow heat conductivity coefficient; in addition, the boric acid ester organosilicon cross-linking agent can also be used as a flame retardant, and can play roles in catalyzing char formation and surface covering flame retardance, so that the flame retardance of the obtained adhesive aerogel fiber is further effectively improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of fibers, and particularly relates to a viscose aerogel fiber and its preparation method and application. Background Art

[0002] With the rapid development of materials science, aerogel materials have shown great potential in the fields of aerospace, energy storage, personal protection, etc. due to their ultra-low density, high porosity, and excellent thermal insulation performance. However, traditional aerogel fibers (such as silica aerogel fibers, polymer-based aerogel fibers) still face many challenges in practical applications. For example, silica aerogel fibers are brittle and have poor mechanical properties, making it difficult to meet the requirements of textile processing; while polymer-based aerogel fibers (such as polyimide aerogel fibers) have better flexibility, but their preparation process is complex, costly, and most rely on organic solvents, resulting in insufficient environmental friendliness. In addition, the flame retardant performance of existing aerogel fibers is insufficient, which limits their application in high-temperature or fire safety fields.

[0003] Viscose fiber, as a regenerated cellulose fiber, has the advantages of wide source, biodegradability, moisture absorption and breathability. However, traditional viscose fibers have poor thermal insulation performance and lack flame retardant function. In recent years, researchers have tried to improve its performance through chemical modification or composite cross-linking agents. For example, introducing siloxane compounds into the viscose spinning solution can improve the heat resistance and mechanical strength of the fiber, but there are still problems such as low cross-linking efficiency and difficulty in further reducing the thermal conductivity; in addition, the porosity of fibers prepared by conventional wet spinning processes is insufficient, resulting in difficulty in balancing thermal insulation performance and lightweight; while freeze-drying technology can construct a high-porosity structure, but the fibers are prone to shrinkage or structural collapse during the drying process, affecting the final performance.

[0004] Therefore, in view of the above problems, there is an urgent need to develop a viscose aerogel fiber with ultra-low thermal conductivity, high mechanical strength, and excellent flame retardant performance. Summary of the Invention

[0005] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide a viscose aerogel fiber and its preparation method and application. The viscose aerogel fiber has ultra-low thermal conductivity, high mechanical strength, and excellent flame retardant performance, can solve the problem of difficult balance between the densification of the traditional fiber structure and porosity, and effectively expands the application prospects of viscose aerogel fibers in the fields of cold protection and fire protection.

[0006] To achieve the purpose of this invention, the following technical solutions are adopted:

[0007] In the first aspect, the present invention provides a viscose aerogel fiber, and the raw materials of the viscose aerogel fiber include viscose and a borate-based organosilicon cross-linking agent.

[0008] The viscose aerogel fiber provided by the present invention adopts an environment-friendly strategy, with viscose as the core raw material, which has a wide source, effectively promotes the concept of sustainable development, and by introducing a borate-based organosilicon cross-linking agent in the raw materials, the borate-based organosilicon cross-linking agent can in-situ generate mesoporous organosilicon during the preparation process, thereby contributing to improving the heat insulation performance and mechanical properties of the obtained viscose aerogel fiber, making it have an ultra-low thermal conductivity; in addition, the borate-based organosilicon cross-linking agent can also be used as a flame retardant, which can play a role in catalytic carbonization and surface coverage of organosilicon for flame retardancy, and thus effectively improves the flame retardancy of the obtained bonded aerogel fiber.

[0009] In the present invention, there is no special requirement for the source of the viscose, and it can be directly purchased as a commercially available product or prepared according to existing methods, but in order to ensure that the obtained viscose aerogel fiber has the best heat insulation performance, mechanical properties and flame retardancy, the following method is preferably used for preparation:

[0010] After soaking the cellulose powder in an aqueous sodium hydroxide solution, the solvent is filtered off, allowed to stand, and then transferred to a closed yellowing kettle, carbon disulfide is added dropwise, and vacuum stirring is carried out. After removing the solvent, orange-yellow cellulose xanthate can be obtained, which is viscose.

[0011] Preferably, the mass percentage content of sodium hydroxide in the aqueous sodium hydroxide solution is 18-20%, such as 18%, 18.5%, 19%, 19.5% or 20%, etc.

[0012] Preferably, the soaking time is 20-30 min, such as 20 min, 22 min, 24 min, 26 min, 28 min or 30 min, etc.

[0013] Preferably, the standing time is 12-24 h, such as 12 h, 14 h, 16 h, 18 h, 20 h, 22 h or 24 h, etc.

[0014] Preferably, the mass ratio of carbon disulfide to cellulose powder is (0.3-0.5):1, such as 0.3:1, 0.32:1, 0.34:1, 0.36:1, 0.38:1, 0.4:1, 0.42:1, 0.44:1, 0.46:1, 0.48:1 or 0.5:1, etc.

[0015] Preferably, the vacuum stirring time is 1-3 h, such as 1 h, 1.2 h, 1.4 h, 1.6 h, 1.8 h, 2 h, 2.2 h, 2.4 h, 2.6 h, 2.8 h or 3 h, etc.

[0016] Preferably, the mass ratio of the viscose to the borate-based organosilicon crosslinking agent is 1:(0.05 - 0.5), such as 1:0.08, 1:0.1, 1:0.15, 1:0.2, 1:0.25, 1:0.3, 1:0.35, 1:0.4, 1:0.45 or 1:0.5, etc., and more preferably 1:(0.1 - 0.35); on the one hand, if the dosage of the borate-based organosilicon crosslinking agent is relatively too low, the crosslinking effect is poor and the production amount of the mesoporous organosilicon is reduced, thus resulting in unsatisfactory heat insulation performance and mechanical properties of the obtained viscose aerogel fiber; on the other hand, if the dosage of the borate-based organosilicon crosslinking agent is relatively too high, agglomeration is likely to occur due to difficult dispersion, resulting in a decrease in the mechanical properties of the obtained viscose aerogel fiber.

[0017] Preferably, the borate-based organosilicon crosslinking agent is prepared by the following method, which includes: dissolving 4-hydroxybenzeneboronic acid in an organic solvent, adding a halogenated silane for reaction, and removing the organic solvent after the reaction to obtain the borate-based organosilicon crosslinking agent.

[0018] Preferably, the molar ratio of the 4-hydroxybenzeneboronic acid to the halogenated silane is 1:(0.5 - 1), such as 1:0.5, 1:0.55, 1:0.6, 1:0.65, 1:0.7, 1:0.75, 1:0.8, 1:0.85, 1:0.9, 1:0.95 or 1:1, etc.

[0019] Preferably, the organic solvent includes any one or a combination of at least two of dimethyl sulfoxide, N,N-dimethylformamide, acetonitrile or tetrahydrofuran.

[0020] Preferably, based on 0.1 mol of the 4-hydroxybenzeneboronic acid, the dosage of the organic solvent is 50 - 100 mL, such as 50 mL, 60 mL, 70 mL, 80 mL, 90 mL or 100 mL, etc.

[0021] Preferably, the halogenated silane includes any one or a combination of at least two of (3-chloropropyl)triethoxysilane, (3-chloropropyl)trimethoxysilane, trimethoxychlorosilane, triethoxychlorosilane, 4-bromobutoxy-terminated polydimethylsiloxane or chloromethyldimethylchlorosilane, and more preferably any one or a combination of at least two of (3-chloropropyl)triethoxysilane, (3-chloropropyl)trimethoxysilane or chloromethyldimethylchlorosilane.

[0022] Preferably, the adding method is dropwise addition.

[0023] Preferably, the addition is carried out under stirring conditions.

[0024] Preferably, the temperature of the reaction is 50 - 90 °C, such as 50 °C, 55 °C, 60 °C, 65 °C, 70 °C, 75 °C, 80 °C, 85 °C or 90 °C, etc.

[0025] Preferably, the time of the reaction is 8 - 12 h, such as 8 h, 8.5 h, 9 h, 9.5 h, 10 h, 10.5 h, 11 h, 11.5 h or 12 h, etc.

[0026] Preferably, the removal of the organic solvent is carried out by suction filtration.

[0027] Preferably, after the removal of the organic solvent, the steps of washing and drying the product are further included.

[0028] In a second aspect, the present invention provides a method for preparing the viscose aerogel fiber as described in the first aspect, and the preparation method includes the following steps:

[0029] (1) Dissolve viscose and a borate-based organosilicon crosslinking agent in an aqueous sodium hydroxide solution to obtain a spinning solution;

[0030] (2) Spin the spinning solution described in step (1), perform multi-fold stretching in a coagulation bath, and obtain the viscose aerogel fiber through freeze-drying.

[0031] Preferably, the mass percentage content of viscose fiber in the spinning solution in step (1) is 5 - 10%, such as 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5% or 10%, etc., and more preferably 7 - 10%.

[0032] Preferably, the pH value of the aqueous sodium hydroxide solution in step (1) is 11 - 13, such as 11, 11.2, 11.4, 11.6, 11.8, 12, 12.2, 12.4, 12.6, 12.8 or 13, etc.

[0033] Preferably, the spinning in step (2) is carried out in a wet spinning device.

[0034] Preferably, the coagulation bath in step (2) is a mixed solution of sulfuric acid, sodium sulfate and water.

[0035] Preferably, the mass ratio of sulfuric acid, sodium sulfate and water is (5 - 10):(5 - 10):(80 - 90), such as 5:5:90, 6:10:84, 7:9:84, 8:8:84, 9:7:84 or 10:6:84, etc.

[0036] Preferably, the draft ratio of the multi-step draft in step (2) is 1 to 1.5 times, such as 1 time, 1.05 times, 1.1 times, 1.15 times, 1.2 times, 1.25 times, 1.3 times, 1.35 times, 1.4 times, 1.45 times or 1.5 times, etc.

[0037] In a third aspect, the present invention provides an application of the viscose aerogel fiber as described in the first aspect in cold-proof and warm-keeping clothing or fire-fighting safety equipment.

[0038] Compared with the prior art, the present invention has the following beneficial effects:

[0039] (1) The raw materials of the viscose aerogel fiber provided by the present invention include viscose and a borate-based organosilicon cross-linking agent. The borate-based organosilicon cross-linking agent can in-situ generate mesoporous organosilicon, effectively improving the heat insulation performance of the obtained viscose aerogel fiber, and reducing its thermal conductivity to 0.018 W·m -1 ·K -1 .

[0040] (2) The borate-based organosilicon cross-linking agent in the viscose aerogel fiber provided by the present invention also plays the role of catalyzing char formation of the boron-based flame retardant and surface covering flame retardancy of organosilicon, improving the flame retardancy of the viscose aerogel fiber, and significantly reducing the peak value of the heat release rate (reduced by about 40% or more) compared with the ordinary viscose aerogel fiber.

[0041] (3) The preparation method of the viscose aerogel fiber provided by the present invention is simple, efficient, controllable and repeatable. The aerogel fiber components are green and environmentally friendly, which is beneficial to the development of functional aerogel fiber textiles and has a wide range of application scenarios in the fields of vehicle interiors, clothing and furniture. Description of the Drawings

[0042] Figure 1 The infrared spectrum of the borate-based organosilicon cross-linking agent provided for Preparation Example 1;

[0043] Figure 2 The nuclear magnetic resonance hydrogen spectrum of the borate-based organosilicon cross-linking agent provided for Preparation Example 1;

[0044] Figure 3 The infrared spectra of the viscose aerogel fibers provided for Example 1 and Comparative Example 1;

[0045] Figure 4 The heat release rate curves of the viscose aerogel fibers provided for Example 1 and Comparative Example 1;

[0046] Figure 5 The heating curve of the viscose aerogel fiber provided for Example 1;

[0047] Figure 6Thermal infrared imaging diagram of the viscose aerogel fiber provided for Example 1. Detailed implementation mode

[0048] The technical solution of the present invention will be further described below through specific implementation modes. Those skilled in the art should understand that the embodiments are only for helping to understand the present invention and should not be regarded as specific limitations to the present invention.

[0049] The raw materials involved in the specific implementation mode of the present invention are all conventional materials in the art without special instructions and can be obtained by purchasing commercially available products.

[0050] Preparation Example 1

[0051] A kind of viscose, its preparation method includes: soaking cellulose powder in a sodium hydroxide solution with a mass fraction of 20% for 25 min, filtering to remove the solvent, standing for 20 h, transferring it to a closed yellowing kettle, dropping carbon disulfide (the mass ratio of cellulose to carbon disulfide is 1:0.4), stirring under vacuum for 2 h, removing the solvent, and obtaining orange-yellow cellulose xanthate, which is viscose.

[0052] Preparation Example 2

[0053] A kind of borate-based organosilicon crosslinking agent, its preparation method includes: weighing 13.79 g (0.1 mol) of 4-hydroxybenzeneboronic acid and dissolving it in 50 mL of dimethyl sulfoxide, dropping 19.87 g (0.1 mol) of (3-chloropropyl)trimethoxysilane, and stirring and reacting at 70 °C for 5 h under the protection of an inert gas. The reaction formula is as follows; after the reaction is completed, filter to remove the solvent, wash the product with ethanol, and then place the product in a vacuum drying oven for drying to obtain a white powdery solid, which is the borate-based organosilicon crosslinking agent;

[0054]

[0055] Structure characterization:

[0056] (1) Fourier transform infrared spectroscopy test: Using a Fourier transform infrared instrument to test the borate-based organosilicon crosslinking agent obtained in Preparation Example 2, and the infrared spectrum diagram of the borate-based organosilicon crosslinking agent provided in Preparation Example 2 obtained by the test is as Figure 1 shown;

[0057] From Figure 1 it can be seen that: an -OH characteristic peak appears at 3187 cm -1 , a -CH3 characteristic peak appears at 2983 cm -1 , a B-O characteristic peak appears at 1438 cm -1 , a C-O-C characteristic peak appears at 1191 cm -1 , and a C-O-C characteristic peak appears at 1041 cm -1A Si-O-Si characteristic peak appeared at [specific position], and a Si-C characteristic peak appeared at 691 cm -1 , which is in line with the molecular bond structure of the target product.

[0058] (2) Nuclear magnetic resonance hydrogen spectrum test: The borate-based organosilicon crosslinking agent obtained in Preparation Example 2 was tested using a nuclear magnetic resonance hydrogen spectrometer, and the nuclear magnetic resonance hydrogen spectrum of the borate-based organosilicon crosslinking agent provided in Preparation Example 2 is as shown in Figure 2 ;

[0059] It can be seen from Figure 2 that: 1.58 - 1.80 ppm (Si-C H 2), 2.53 - 2.62 ppm (Si-CH2C H 2), 2.75 ppm (Si-CH2CH2C H 2), 2.81 - 3.03 ppm (Si-OC H 3), 7.79 - 7.85 ppm is the characteristic peak of the benzene ring. The H element at the above "_" position has a corresponding relationship with the spectrum, which is in line with the molecular structure characteristics of the target product.

[0060] In summary, it can be proved that the target product was successfully prepared in Preparation Example 2.

[0061] Preparation Example 3

[0062] A borate-based organosilicon crosslinking agent, which is different from Preparation Example 2 only in that (3-chloropropyl)triethoxysilane is used to replace (3-chloropropyl)trimethoxysilane, and other substances, dosages and preparation methods are the same as those in Preparation Example 2.

[0063] Preparation Example 4

[0064] A borate-based organosilicon crosslinking agent, which is different from Preparation Example 2 only in that 4-bromobutoxy-terminated polydimethylsiloxane is used to replace (3-chloropropyl)trimethoxysilane, and other substances, dosages and preparation methods are the same as those in Preparation Example 2.

[0065] Preparation Example 5

[0066] A borate-based organosilicon crosslinking agent, which is different from Preparation Example 2 only in that chloromethyldimethylchlorosilane is used to replace (3-chloropropyl)trimethoxysilane, and other substances, dosages and preparation methods are the same as those in Preparation Example 2.

[0067] Example 1

[0068] A viscose aerogel fiber, the raw materials of which include viscose (Preparation Example 1) and a borate-based organosilicon crosslinking agent (Preparation Example 2) with a mass ratio of 1:0.25;

[0069] The preparation method of the viscose aerogel fiber provided in this embodiment includes the following steps:

[0070] (1) Dissolve the viscose obtained in Preparation Example 1 in an aqueous sodium hydroxide solution with a pH value of 12 to obtain a viscose solution with a mass percentage content of 8%;

[0071] (2) Add 2 g of the borate-based organosilicon crosslinking agent obtained in Preparation Example 2 to 100 g of the viscose solution obtained in step (1) to obtain a spinning solution;

[0072] (3) Place the spinning solution obtained in step (2) in a wet spinning device for spinning. The spinning parameters are as follows: the extrusion rate is 30 μL / min, the inner diameter of the spinning needle is 0.52 mm, the coagulation bath is a mixed solution of H2SO4, Na2SO4, and H2O with a mass ratio of 0.5:0.5:9. The wet fiber obtained by spinning is drawn by a drawing winder, and the drawing ratio is 1.5 times. After the drawn wet fiber is frozen in liquid nitrogen for 3 min, it is dried in a freeze dryer for 24 h to obtain the viscose aerogel fiber.

[0073] Example 2

[0074] A viscose aerogel fiber, which is different from that in Example 1 in that the amount of the borate-based organosilicon crosslinking agent in step (2) of the preparation method is adjusted to 0.5 g, so that the mass ratio of viscose to the borate-based organosilicon crosslinking agent in the raw materials of the viscose aerogel fiber is 1:0.0625, and other substances, amounts, and steps are the same as those in Example 1.

[0075] Example 3

[0076] A viscose aerogel fiber, which is different from that in Example 1 in that the amount of the borate-based organosilicon crosslinking agent in step (2) of the preparation method is adjusted to 1 g, so that the mass ratio of viscose to the borate-based organosilicon crosslinking agent in the raw materials of the viscose aerogel fiber is 1:0.125, and other substances, amounts, and steps are the same as those in Example 1.

[0077] Example 4

[0078] A viscose aerogel fiber, which is different from that in Example 1 in that the amount of the borate-based organosilicon crosslinking agent in step (2) of the preparation method is adjusted to 1.5 g, so that the mass ratio of viscose to the borate-based organosilicon crosslinking agent in the raw materials of the viscose aerogel fiber is 1:0.188, and other substances, amounts, and steps are the same as those in Example 1.

[0079] Example 5

[0080] A viscose aerogel fiber, which is different from Example 1 in that the amount of the borate-based organosilicon crosslinking agent in step (2) of the preparation method is adjusted to 2.5 g, so that the mass ratio of viscose to the borate-based organosilicon crosslinking agent in the raw materials of the viscose aerogel fiber is 1:0.313, and other substances, amounts and steps are the same as those in Example 1.

[0081] Example 6

[0082] A viscose aerogel fiber, which is different from Example 1 in that the amount of the borate-based organosilicon crosslinking agent in step (2) of the preparation method is adjusted to 3 g, so that the mass ratio of viscose to the borate-based organosilicon crosslinking agent in the raw materials of the viscose aerogel fiber is 1:0.375, and other substances, amounts and steps are the same as those in Example 1.

[0083] Example 7

[0084] A viscose aerogel fiber, which is different from Example 1 in that the mass percentage content of viscose in the viscose solution in step (1) of the preparation method is adjusted to 6%, and the addition amount of the borate-based organosilicon crosslinking agent in step (2) of the preparation method is adjusted to 1.5 g, so that the mass ratio of viscose to the borate-based organosilicon crosslinking agent in the raw materials of the viscose aerogel fiber remains 1:0.25, and other substances, amounts and steps are the same as those in Example 1.

[0085] Example 8

[0086] A viscose aerogel fiber, which is different from Example 1 in that the mass percentage content of viscose in the viscose solution in step (1) of the preparation method is adjusted to 7%, and the addition amount of the borate-based organosilicon crosslinking agent in step (2) of the preparation method is adjusted to 1.75 g, so that the mass ratio of viscose to the borate-based organosilicon crosslinking agent in the raw materials of the viscose aerogel fiber remains 1:0.25, and other substances, amounts and steps are the same as those in Example 1.

[0087] Example 9

[0088] A viscose aerogel fiber, which is different from Example 1 in that the mass percentage content of viscose in the viscose solution in step (1) of the preparation method is adjusted to 9%, and the addition amount of the borate-based organosilicon crosslinking agent in step (2) of the preparation method is adjusted to 2.25 g, so that the mass ratio of viscose to the borate-based organosilicon crosslinking agent in the raw materials of the viscose aerogel fiber remains 1:0.25, and other substances, amounts and steps are the same as those in Example 1.

[0089] Example 10

[0090] A viscose aerogel fiber, which is different from that of Example 1 in that the mass percentage of viscose in the viscose solution in step (1) of the preparation method is adjusted to 10%, and the addition amount of the borate-based organosilicon crosslinking agent in step (2) of the preparation method is adjusted to 2.5 g, so that the mass ratio of the raw viscose and the borate-based organosilicon crosslinking agent of the viscose aerogel fiber is maintained at 1:0.25, and other substances, dosages and steps are the same as those in Example 1.

[0091] Example 11

[0092] A viscose aerogel fiber, which is different from that of Example 1 in that the borate-based organosilicon crosslinking agent obtained in Preparation Example 3 is used to replace the borate-based organosilicon crosslinking agent obtained in Preparation Example 2, and other substances, dosages and steps are the same as those in Example 1.

[0093] Example 12

[0094] A viscose aerogel fiber, which is different from that of Example 1 in that the borate-based organosilicon crosslinking agent obtained in Preparation Example 4 is used to replace the borate-based organosilicon crosslinking agent obtained in Preparation Example 2, and other substances, dosages and steps are the same as those in Example 1.

[0095] Example 13

[0096] A viscose aerogel fiber, which is different from that of Example 1 in that the borate-based organosilicon crosslinking agent obtained in Preparation Example 5 is used to replace the borate-based organosilicon crosslinking agent obtained in Preparation Example 2, and other substances, dosages and steps are the same as those in Example 1.

[0097] Comparative Example 1

[0098] A viscose aerogel fiber, the raw materials of which include viscose;

[0099] The preparation method of the viscose aerogel fiber provided in this comparative example includes the following steps:

[0100] (1) Dissolve the viscose obtained in Preparation Example 1 in an aqueous sodium hydroxide solution with a pH value of 12 to obtain a viscose solution with a mass percentage of 8%;

[0101] (2) Use the viscose solution obtained in step (1) as a spinning solution and place it in a wet spinning device for spinning. The spinning parameters are as follows: the extrusion rate is 30 μL / min, the inner diameter of the spinning needle is 0.52 mm, the coagulation bath is a mixed solution of H2SO4, NaSO4 and H2O with a mass ratio of 0.5:0.5:9. The wet fiber obtained by spinning is drawn by a draw-winding machine, and the draw ratio is 1.5 times. After the drawn wet fiber is frozen in liquid nitrogen for 3 min, it is dried in a freeze dryer for 24 h to obtain the viscose aerogel fiber.

[0102] (I) Structural characterization

[0103] Fourier transform infrared spectroscopy test: The viscose aerogel fibers provided in Example 1 and the viscose aerogel fibers provided in Comparative Example 1 were tested using a Fourier transform infrared spectrometer. The infrared spectra of the viscose aerogel fibers provided in Example 1 and Comparative Example 1 are as shown in Figure 3 the following figure;

[0104] As can be seen from Figure 3 the figure: The viscose aerogel fibers provided in Example 1 showed typical absorption peaks of ordinary viscose aerogel fibers (Comparative Example 1): at 3338 (-OH str ) cm -1 , 2892 (-CH 2str ) cm -1 , 1314 (-OH bend ) cm -1 , 1157 (C-O str ) cm -1 and 1020 (C-C str ) cm -1 respectively. Moreover, an absorption peak of the B-O bond appeared at 1438 cm -1 in the infrared absorption curve of the viscose aerogel fibers provided in Example 1, indicating that the borate-based organosilicon crosslinking agent had been successfully dispersed inside the aerogel fibers.

[0105] (II) Performance test

[0106] (1) The viscose aerogel fibers provided in Example 1 and the viscose aerogel fibers provided in Comparative Example 1 were tested using a microcalorimeter with a heating rate of 1 °C / s, a test temperature range of 100 - 800 °C, and a sample mass of 5 - 10 mg. The heat release rate curves of the viscose aerogel fibers provided in Example 1 and Comparative Example 1 are as shown in Figure 4 the following figure;

[0107] As can be seen from Figure 4 the figure: The peak heat release rate of the viscose aerogel fibers provided in Example 1 was reduced by approximately 41.9% compared to the peak heat release rate of the viscose aerogel fibers provided in Comparative Example 1, indicating that the viscose aerogel fibers provided in Example 1 had more excellent flame retardant performance compared to the viscose aerogel fibers provided in Comparative Example 1.

[0108] (2) The heating rate of the viscose aerogel fibers provided in Example 1 was tested using a probe thermometer. The test method was as follows: The viscose aerogel fibers provided in Example 1 were woven into a plain fabric, stacked in multiple layers to a height of 0.5 cm, placed on the surface of a 90 °C hot stage, and the test time was 30 s. The heating curve of the viscose aerogel fibers provided in Example 1 is as shown in Figure 5 the following figure;

[0109] As can be seen fromFigure 5 It can be seen that: the viscose aerogel fiber provided in Example 1 has a slow heating rate after being heated at 90 °C for 30 s, indicating that the viscose aerogel fiber provided in Example 1 has excellent heat insulation performance.

[0110] (3) Use an infrared thermal imager to perform surface infrared radiation testing on the viscose aerogel fiber provided in Example 1. The testing method is as follows: weave the viscose aerogel fiber provided in Example 1 into a plain weave fabric, stack multiple layers to a height of 0.5 cm, place it on the surface of a 90 °C hot stage, and take an infrared thermal imaging picture after heating for 30 s. The thermal infrared imaging diagram of the viscose aerogel fiber provided in Example 1 obtained by testing is as Figure 6 shown;

[0111] From Figure 6 it can be seen that: the viscose aerogel fiber provided in Example 1 has excellent heat insulation performance.

[0112] (4) Test the viscose aerogel fibers provided in Examples 1 to 13 and Comparative Example 1 according to the following test methods ① to ④, and the test data are statistically shown in Table 1;

[0113] ① Thermal conductivity: Use a thermal conductivity meter to test the thermal conductivity of the sample. The test temperature range is from room temperature to 100 °C, and each temperature point is tested in parallel 4 times. The test atmosphere is air. The aerogel fiber is woven into a plain weave fabric and tested after being stacked to a thickness of 0.5 cm;

[0114] ② Maximum heat release rate: Use a microcalorimeter to test the viscose aerogel fiber. The heating rate is 1 °C / s, the test temperature range is 100 to 800 °C, and the sample mass is 5 to 10 mg;

[0115] ③ Temperature difference under a 90 °C background and temperature difference under a -100 °C background: Use a probe thermometer to test the heating rate of the viscose aerogel fiber. The test method is as follows: weave the viscose aerogel fiber into a plain weave fabric, stack multiple layers to a height of 0.5 cm, place it on the surface of a 90 °C hot stage and the surface of an ice stage at -100 °C after being cooled by liquid nitrogen, and the test time is 30 s;

[0116] ④ Mechanical strength: Use an electronic universal testing machine to test the mechanical properties of the sample. The test spacing is 20 mm and the tensile speed is 2 mm / s.

[0117] Table 1

[0118]

[0119]

[0120] It can be seen from the data in Table 1 that:

[0121] ① Compared with the ordinary viscose aerogel fiber without borate-based silicone crosslinking agent provided in Comparative Example 1, the thermal conductivities of the viscose aerogel fibers provided in Examples 1 to 13 are all reduced, indicating a significant increase in heat insulation performance, and the maximum heat release rate is reduced, indicating more excellent flame retardant performance. In addition, the temperature difference under different temperature backgrounds is also significantly increased, which also indicates more excellent heat insulation performance.

[0122] ② By comparing the data of Examples 1 to 6, it can be seen that with other conditions unchanged, as the addition amount of borate-based silicone crosslinking agent increases, the thermal conductivity of the obtained viscose aerogel fiber first decreases and then increases, indicating that the heat insulation effect first improves and then decreases. This is because the addition of excessive borate-based silicone crosslinking agent may damage the internal skeleton structure of the viscose aerogel fiber, resulting in the collapse of the internal structure of the obtained viscose aerogel fiber, indicating that the addition amount of borate-based silicone crosslinking agent should not be too high or too low.

[0123] ③ By comparing the data of Example 1 and Examples 7 to 10 again, it can be seen that with other conditions unchanged, as the concentration of viscose in the spinning solution increases, the thermal conductivity of the obtained viscose aerogel fiber also first decreases and then increases, indicating that the heat insulation effect first improves and then decreases. This may be due to the excessive increase in the concentration of the spinning solution reducing the porosity inside the viscose aerogel fiber, resulting in a decrease in the internal pore structure.

[0124] ④ Finally, by comparing the data of Example 1 and Examples 11 to 13, it can also be seen that with other conditions unchanged, changing the type of borate-based organic crosslinking agent, the thermal conductivities of the prepared viscose aerogel fibers are not exactly the same; among them, the mechanical properties of the viscose aerogel fiber obtained in Example 12 are relatively poor, which may be due to the fact that 4-bromobutoxy-terminated polydimethylsiloxane is a polymer with a relatively large molecular weight, resulting in a poor crosslinking effect under the same mass addition amount.

[0125] The applicant declares that the present invention illustrates a viscose aerogel fiber and its preparation method and application through the above examples, but the present invention is not limited to the above process steps, that is, it does not mean that the present invention must rely on the above process steps to be implemented. Those skilled in the art should understand that any improvement to the present invention, the equivalent substitution of the raw materials selected for the present invention, the addition of auxiliary components, and the selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A viscose aerogel fiber, characterized in that, The raw materials of the viscose aerogel fiber include viscose and a borate-based organosilicon crosslinking agent.

2. The viscose aerogel fiber according to claim 1, wherein The mass ratio of the viscose to the borate-based organosilicon crosslinking agent is 1:(0.05 - 0.5), preferably 1:(0.1 - 0.35).

3. The viscose aerogel fiber according to claim 1 or 2, characterized in that, The borate-based organosilicon crosslinking agent is prepared by the following method, which includes: dissolving 4-hydroxybenzeneboronic acid in an organic solvent, adding a halogenated silane for reaction, and removing the organic solvent after the reaction is completed to obtain the borate-based organosilicon crosslinking agent; Preferably, the molar ratio of the 4-hydroxybenzeneboronic acid to the halogenated silane is 1:(0.5 - 1); Preferably, the halogenated silane includes any one or a combination of at least two of (3-chloropropyl)triethoxysilane, (3-chloropropyl)trimethoxysilane, trimethoxychlorosilane, triethoxychlorosilane, 4-bromobutoxy-terminated polydimethylsiloxane, or chloromethyldimethylchlorosilane, and further preferably any one or a combination of at least two of (3-chloropropyl)triethoxysilane, (3-chloropropyl)trimethoxysilane, or chloromethyldimethylchlorosilane; Preferably, the temperature of the reaction is 50 - 90 °C and the time is 8 - 12 h.

4. A method for preparing the viscose aerogel fiber according to any one of claims 1 to 3, characterized in that, The preparation method includes the following steps: (1) Dissolve the viscose and the borate-based organosilicon crosslinking agent in an aqueous sodium hydroxide solution to obtain a spinning solution; (2) Spin the spinning solution obtained in step (1), perform multiple stretching in a coagulation bath, and obtain the viscose aerogel fiber after freeze-drying.

5. The preparation method according to claim 4, wherein The mass percentage content of the viscose fiber in the spinning solution in step (1) is 5 - 10%, preferably 7 - 10%.

6. The preparation method according to claim 4 or 5, characterized in that, The pH value of the aqueous sodium hydroxide solution in step (1) is 11 - 13.

7. The preparation method according to any one of claims 4 to 6, characterized in that, The spinning in step (2) is carried out in a wet spinning device.

8. The preparation method according to any one of claims 4 to 7, characterized in that The coagulation bath in step (2) is a mixed solution of sulfuric acid, sodium sulfate, and water; Preferably, the mass ratio of the sulfuric acid, sodium sulfate, and water is (5 - 10):(5 - 10):(80 - 90).

9. The preparation method according to any one of claims 4 to 8, characterized in that, The stretching ratio of the multiple stretching in step (2) is 1 - 1.5 times.

10. Application of the viscose aerogel fiber according to any one of claims 1 - 3 in cold-proof and warm-keeping clothing or fire-fighting safety equipment.

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