Preparation method of regenerated cellulose fiber with phase change temperature control based on silica aerogel

Abstract

The application belongs to the technical field of functional fiber materials, and particularly relates to a preparation method of silica aerogel-based phase change temperature control regenerated cellulose fibers, which comprises preparation of amino-modified silica aerogel, preparation of a phase change material solution, vacuum impregnation, preparation of a blended spinning solution, spinning forming and post-treatment. In the vacuum impregnation process, the phase change material, isophorone diisocyanate and dibutyltin dilaurate in the phase change material solution are fully adsorbed and diffused into the pore structure of the amino-modified silica aerogel, and after suction filtration, a surface enhancer is added to make the amino-modified silica aerogel fully contact with the isophorone diisocyanate and the dibutyltin dilaurate, heat preservation and solidification are performed, the amino groups on the surface and in the interior of the aerogel are crosslinked with the isophorone diisocyanate, and after solidification, the crosslinked structure on the surface and in the pores plays a certain binding role on the phase change material, so that the melting loss caused by the excessively high temperature of a coagulation bath is avoided.

Description

Technical Field

[0001] This invention belongs to the field of functional fiber materials technology, specifically relating to a method for preparing silica aerogel-based phase change temperature-controlled regenerated cellulose fiber. Background Technology

[0002] The rapid development of science and technology has provided favorable conditions for the textile industry to develop high-tech textile raw materials. With the improvement of people's living standards, differentiated and functional textiles have been widely used in various sectors of the national economy. Fiber materials with temperature control functions are highly favored due to their alignment with green, low-carbon, and environmentally friendly consumption concepts. Phase change energy storage temperature-regulating fibers absorb or release heat during the phase change process through internal phase change materials, achieving bidirectional automatic temperature regulation. This is a new type of intelligent temperature-controlled textile material that can spontaneously absorb and release heat within a specific ambient temperature range. In 2006, Outlast Inc. of the United States collaborated with Kelheim Fibers of Germany to successfully combine phase change microcapsule technology with viscose fiber production technology to produce Outlast phase change temperature-regulating fibers. Domestically, many research institutes and enterprises have also carried out microcapsule-encapsulated phase change materials such as paraffin to develop phase change energy storage fibers. Limited by the low mechanical properties of viscose fiber and the limited amount of phase change microcapsule components added during the production process, the enthalpy value of the prepared fiber is low. At the same time, during subsequent dyeing, finishing, and weaving processes, factors such as high temperature, friction, or extrusion may cause capsule breakage and loss of phase change materials.

[0003] Aerogels possess excellent structural properties, making them suitable as carriers for the adsorption, control, and regulation of reagents and drugs. SiO2 aerogels exhibit a porosity exceeding 80%, and their three-dimensional network structure results in a specific surface area of ​​800-1000 m². 2With a pore size of approximately 15 nm, silica aerogel micropowder exhibits great potential in the adsorption field, capable of efficiently adsorbing a variety of substances. Patent CN202411262371.7 discloses the preparation of phase change materials by vacuum adsorption of octadecane, a liquid phase change material, from silica aerogel micropowder. CN202411069874.2 discloses the addition of 3-aminopropyltriethoxysilane and deionized water to a mixed solution of terephthalaldehyde, octadecyl alcohol, and anhydrous ethanol, followed by stirring, high-pressure reactor reaction, and drying to obtain octadecyl alcohol / silica aerogel phase change material. CN202410506374.4 discloses a method for preparing modified silica-encapsulated paraffin phase change nanocapsules. CN201710740613.2 discloses the use of trimethylmethoxysilane as a novel precursor to prepare flexible silica aerogel, followed by the selection of a suitable phase change core material and a vacuum impregnation method to obtain a silica aerogel-based phase change composite material. Patent CN202210214589.X discloses a process in which organically bridging groups and end-group-functionalized silane monomers are uniformly mixed in a mixed solvent of ethanol and water. A phase change material (phase change temperature around 80-90℃, enthalpy 220-250 J / g) and inorganic fibers are then added. The mixture is transferred to a stainless steel high-pressure reactor for high-temperature reaction, and the product is then dried at 60-70℃ to obtain a fiber-reinforced silica aerogel-based composite phase change insulation material. This invention demonstrates that silica aerogel can serve as a carrier for phase change materials and can be applied to the preparation of phase change materials.

[0004] However, in practical applications, adding silica aerogel as a carrier for phase change materials to cellulose fibers has the following drawbacks: silica aerogel is brittle and has poor compatibility with cellulose macromolecules, which can easily affect the mechanical properties of cellulose fibers; the coagulation bath temperature is high, and the phase change material is easily melted and lost from the carrier; the viscose spinning solution is highly alkaline, which can cause corrosion and collapse of the pore structure of silica aerogel, affecting the loading effect on the phase change material. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention proposes a method for preparing silica aerogel-based phase change temperature-controlled regenerated cellulose fibers. This method solves the problem of decreased fiber mechanical properties caused by silica aerogel, improves the defect of easy loss of phase change materials in the coagulation bath, and further enhances the temperature control capability of phase change fibers by utilizing the excellent heat insulation and heat preservation effect of silica aerogel.

[0006] A method for preparing silica aerogel-based phase change temperature-controlled regenerated cellulose fiber, the method comprising the following steps:

[0007] S1. Preparation of amino-modified silica aerogel

[0008] Tetraethyl orthosilicate, anhydrous ethanol, and deionized water were mixed and stirred until homogeneous. Nitric acid solution was added to adjust the pH to 2-4, and hydrolysis was carried out for 2-3 hours to form a sol. Ammonia solution was then added to adjust the pH to 6-7, and 3-aminopropyltrihydroxysilane was added to carry out a condensation reaction until a wet gel was formed. After aging, solvent replacement, and supercritical CO2 drying, amino-modified silica aerogel was obtained with an average pore size of 21-27 nm and a porosity of over 90%.

[0009] Preferably, the molar ratio of tetraethyl orthosilicate, anhydrous ethanol, and deionized water is 1:12 to 15:4 to 6.

[0010] Preferably, the concentration of the nitric acid solution is 0.5–1 mol / L, and the concentration of the ammonia solution is 0.1–0.2 mol / L.

[0011] Preferably, the molar ratio of 3-aminopropyltrihydroxysilane to tetraethyl orthosilicate is 1:1.5 to 2.

[0012] Preferably, the aging process is carried out at room temperature for 36 to 48 hours.

[0013] Preferably, the solvent replacement uses anhydrous ethanol or n-hexane, and the solvent is replaced once every 10 to 14 hours, for a total of 3 to 5 times.

[0014] S2, Preparation of phase change material solutions

[0015] Phase change material, isophorone diisocyanate, and dibutyltin dilaurate are added to anhydrous n-hexane, heated to 60-65°C, and stirred for 50-60 minutes to dissolve, thus obtaining a phase change material solution.

[0016] Preferably, the phase change material is n-octadecane and paraffin, wherein the amount of paraffin added is 5 to 10% of the mass of n-octadecane.

[0017] Preferably, the paraffin wax used is 48#, 50#, 52# or a mixture thereof. The melting point of paraffin wax is usually between 47℃ and 64℃, while the melting point of n-octadecane is usually around 28℃. The addition of paraffin wax can prevent the phase change mixture from easily crystallizing under supercooled conditions.

[0018] Preferably, the mass ratio of the phase change material to the amino-modified silica aerogel in the phase change material solution is 1 to 1.5:1.

[0019] Preferably, the molar ratio of isophorone diisocyanate in the phase change material solution to amino group in the amino-modified silica aerogel is 0.4 to 0.5:1.

[0020] Preferably, the amount of dibutyltin dilaurate added is 0.1 to 0.2% of the mass of isophorone diisocyanate.

[0021] S3, Vacuum Impregnation

[0022] Amino-modified silica aerogel was added to a reaction vessel, heated, stirred, and evacuated. Then, a phase change material solution was added, and the mixture was vacuum impregnated for 2–3 hours. After impregnation, the mixture was cooled at 10–15°C for 40–60 minutes and filtered to obtain a composite aerogel. The composite aerogel was then added to a surface reinforcing agent and impregnated for another 20–30 minutes before being filtered. The mixture was then kept at 40–50°C for 4–6 hours to ensure complete surface and internal cross-linking, thus obtaining silica aerogel-based phase change energy storage microparticles.

[0023] Preferably, the heating temperature is 60-70℃, the stirring speed is 200-300 r / min, and the vacuum degree is ≤-0.08MPa.

[0024] Preferably, the concentration of isophorone diisocyanate in the surface enhancer is 7-12 g / L, the concentration of dibutyltin dilaurate is 0.01-0.02 g / L, and the solvent is anhydrous ethanol.

[0025] Preferably, the ratio of the composite aerogel to the surface enhancer is 1:3 to 5.

[0026] Isophorone diisocyanate and dibutyltin dilaurate were added to the phase change material solution, where dibutyltin dilaurate activated the -NCO in isophorone diisocyanate. The surface and porous structure of the amino-modified silica aerogel were modified with a large number of amino groups by 3-aminopropyltrihydroxysilane, which laid the foundation for subsequent surface and pore crosslinking. During vacuum impregnation, the phase change material, isophorone diisocyanate, and dibutyltin dilaurate in the phase change material solution are fully adsorbed and diffused into the porous structure of the amino-modified silica aerogel. After filtration, a surface reinforcing agent is added to ensure full contact between the amino-modified silica aerogel and the isophorone diisocyanate and dibutyltin dilaurate. The aerogel is then cured at 40–50°C. At this temperature, the phase change material is in a semi-solid state, which simultaneously accelerates the cross-linking and curing rate of the amino groups and isophorone diisocyanate on the aerogel surface and inside. After curing, the cross-linked structure on the surface and in the pores provides a certain degree of constraint for the phase change material, preventing melting and loss due to excessive temperature, and reducing the corrosive effect of the alkaline spinning solution on the aerogel pores, thus better loading the phase change material. The cross-linked structure on the surface of the silica aerogel-based phase change energy storage microparticles improves the compatibility between the aerogel and cellulose macromolecules. Simultaneously, the cross-linked structure formed inside the aerogel acts as a filler, significantly improving the aerogel's brittleness.

[0027] S4. Preparation of blend spinning solution

[0028] Silica aerogel-based phase change energy storage microparticles and nonionic surfactants were added to deionized water and stirred to disperse them, thus obtaining a silica aerogel-based phase change energy storage microparticle dispersion.

[0029] A dissolving slurry with a degree of polymerization of 800-1000 was selected, and a cellulose viscose solution was prepared using the CS2 sulfonation process. A silica aerogel-based phase change energy storage microparticle dispersion was added to the cellulose viscose solution in proportion before spinning and mixed evenly to prepare a blended spinning solution.

[0030] Preferably, the nonionic surfactant is one or more of Tween-80, Span-60, Span-80, and OP50, and the amount added is 2 to 4% of the mass of the silica aerogel-based phase change energy storage microparticles.

[0031] Preferably, the dissolving pulp is one of cotton pulp, wood pulp, or bamboo pulp.

[0032] Preferably, the cellulose viscose solution has a viscosity of 80–90 s (falling ball method), a maturity of 30–40 mL (10% NH4Cl), a cellulose content of 6.8–8.0 wt%, and a sodium hydroxide content of 5.6–7.2 wt%. By selecting a high-viscosity cellulose viscose solution, the reduction in system viscosity caused by the addition of silica aerogel-based phase change energy storage microparticle dispersion is reduced, ensuring subsequent spinnability and fiber mechanical properties.

[0033] Preferably, the amount of silica aerogel-based phase change energy storage microparticle dispersion added is calculated as 18-25 wt% of the silica aerogel-based phase change energy storage microparticles in the silica aerogel-based phase change energy storage microparticle dispersion as the percentage of cellulose content in the cellulose viscose solution.

[0034] S5, spinning and forming

[0035] After the blended spinning solution is ejected from the spinneret, it is formed and drawn into nascent fiber bundles in the first coagulation bath. The bundles are further formed and drawn in the second bath, and then enter the third bath for plasticizing and drawing. The bundles are then bundled and drawn into the post-processing process.

[0036] Preferably, in the coagulation bath, the sulfuric acid is 15-20 g / L, the sodium sulfate is 65-85 g / L, the zinc sulfate is 0.1-0.5 g / L, the reaction temperature is 31-33°C, and the stretching in the coagulation bath is controlled at -20 to 0%.

[0037] Preferably, the sulfuric acid in the second bath is 40-50 g / L, the bath temperature is controlled at 40-50°C, and the stretching in the second bath is controlled at 60-80%.

[0038] Preferably, the sulfuric acid in the three baths is 10-15 g / L, the bath temperature is controlled at 95-100℃, and the stretching in the three baths is controlled at 8-12%.

[0039] Preferably, the spinning speed in the first, second, and third coagulation baths is 30–35 m / min.

[0040] The temperature, composition, and draw distribution of each coagulation bath are crucial to the formation of fiber bundles. Sulfuric acid can decompose cellulose sulfonate to generate regenerated cellulose, sodium sulfate promotes viscose coagulation and formation, and zinc sulfate reacts with sodium cellulose sulfonate to generate zinc cellulose sulfonate with a uniform and fine crystalline structure. A gentle spinning process reduces the rate of coagulation and decomposition within the viscose stream, delaying cellulose regeneration and resulting in a uniform and dense fiber structure. This also creates conditions for multi-stage high-ratio draw, which gives the regenerated fibers a highly oriented and low-side-order microcrystalline dense structure, improving fiber strength and reducing the impact of phase change material particles on fiber mechanical properties.

[0041] S6, Post-processing

[0042] After three baths of stretching, the fibers are washed, desulfurized, bleached, oiled, dried, and wound to obtain silica aerogel-based phase change temperature-controlled regenerated cellulose fibers.

[0043] By adopting the above technical solution, the technical effect achieved by this invention is as follows:

[0044] 1. The phase change temperature-controlled regenerated cellulose fiber prepared by this invention has a fineness of 1.33–3.33 dtex, a dry breaking strength of 2.3–2.61 cN / dtex, and a wet breaking strength of 1.19–1.36 cN / dtex; its enthalpy value is ≥16 J / g. The temperature rise and fall difference ΔT compared with ordinary viscose fiber is... max It has a temperature control performance of ≥4.0 ℃, and the enthalpy value does not change much after 50 water washes, indicating durable temperature control performance.

[0045] 2. The silica aerogel-based phase change energy storage microparticles prepared by this invention play a good protective role for phase change materials, and the loss rate during fiber preparation is less than 1.0%.

[0046] 3. This invention utilizes a three-stage coagulation bath, which makes the spinning process more gentle and achieves uniform encapsulation of silica aerogel-based phase change energy storage microparticles inside the fiber, thereby improving the bonding effect and compatibility between silica aerogel-based phase change energy storage microparticles and the fiber. Attached Figure Description

[0047] Figure 1 This is a graph showing the temperature control trend of the cellulose fibers prepared in Example 1;

[0048] Figure 2 This is a graph showing the temperature control trend of the cellulose fibers prepared in Example 2;

[0049] Figure 3 This is a graph showing the temperature control trend of the cellulose fibers prepared in Example 3. Detailed Implementation

[0050] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with the accompanying drawings and preferred embodiments, is provided below.

[0051] Example 1: A method for preparing silica aerogel-based phase change temperature-controlled regenerated cellulose fiber, the preparation method comprising the following steps:

[0052] S1. Preparation of amino-modified silica aerogel

[0053] Tetraethyl orthosilicate, anhydrous ethanol, and deionized water were mixed and stirred until homogeneous. Nitric acid solution was added to adjust the pH to 3, and hydrolysis was carried out for 2.5 hours to form a sol. Ammonia solution was then added to adjust the pH to 6.5, and 3-aminopropyltrihydroxysilane was added to carry out a condensation reaction until a wet gel was formed. After aging, solvent replacement, and supercritical CO2, amino-modified silica aerogel was obtained with an average pore size of 23 nm and a porosity of 93%.

[0054] The molar ratio of tetraethyl orthosilicate, anhydrous ethanol, and deionized water is 1:13:5.

[0055] The concentration of the nitric acid solution is 0.7 mol / L, and the concentration of the ammonia solution is 0.15 mol / L.

[0056] The molar ratio of 3-aminopropyltrihydroxysilane to tetraethyl orthosilicate is 1:1.7.

[0057] The aging process was carried out at room temperature for 40 hours.

[0058] The solvent replacement was performed using n-hexane, with the solvent being replaced every 12 hours for a total of 5 times.

[0059] S2, Preparation of phase change material solutions

[0060] Phase change material, isophorone diisocyanate, and dibutyltin dilaurate were added to anhydrous n-hexane, heated to 65°C, and stirred for 60 minutes to dissolve, thus obtaining a phase change material solution.

[0061] The phase change material is n-octadecane and 48# paraffin, wherein the amount of 48# paraffin added is 8% of the mass of n-octadecane.

[0062] The mass ratio of the phase change material to anhydrous n-hexane is 1:4.

[0063] The mass ratio of the phase change material to the amino-modified silica aerogel in the phase change material solution is 1.2:1.

[0064] The molar ratio of isophorone diisocyanate in the phase change material solution to amino groups in the amino-modified silica aerogel is 0.45:1.

[0065] The amount of dibutyltin dilaurate added is 0.15% of the mass of isophorone diisocyanate.

[0066] S3, Vacuum Impregnation

[0067] Amino-modified silica aerogel was added to a reaction vessel, heated, stirred, and evacuated. Then, a phase change material solution was added, and the mixture was vacuum impregnated for 2.5 h. After impregnation, the mixture was cooled at 12 °C for 50 min and filtered to obtain a composite aerogel. The composite aerogel was then added to a surface reinforcing agent and impregnated for another 25 min before being filtered. The mixture was then kept at 45 °C for 5 h to obtain silica aerogel-based phase change energy storage microparticles.

[0068] The heating temperature is 65℃, the stirring speed is 250r / min, and the vacuum degree is -0.08MPa.

[0069] The surface enhancer contains isophorone diisocyanate at a concentration of 10 g / L, dibutyltin dilaurate at a concentration of 0.015 g / L, and anhydrous ethanol as the solvent.

[0070] The ratio of the composite aerogel to the surface enhancer is 1:4.

[0071] S4. Preparation of blend spinning solution

[0072] Silica aerogel-based phase change energy storage microparticles and nonionic surfactants were added to deionized water and stirred to disperse them, thus obtaining a silica aerogel-based phase change energy storage microparticle dispersion.

[0073] Wood pulp with a degree of polymerization of 900 was selected and cellulose viscose solution was prepared by CS2 sulfonation process. Silica aerogel-based phase change energy storage microparticle dispersion was added to the cellulose viscose solution in proportion before spinning and mixed evenly to prepare a blended spinning solution.

[0074] The nonionic surfactant is Tween-80, and the amount added is 3% of the mass of the silica aerogel-based phase change energy storage microparticles.

[0075] The cellulose viscose solution has a viscosity of 85s (falling ball method), a maturity of 35mL (10% NH4Cl), a cellulose content of 7.5wt%, and a sodium hydroxide content of 6.4wt%.

[0076] The amount of silica aerogel-based phase change energy storage microparticle dispersion added is calculated as 18 wt% of the silica aerogel-based phase change energy storage microparticles in the cellulose viscose solution.

[0077] S5, spinning and forming

[0078] After the blended spinning solution is ejected from the spinneret, it is formed and drawn into nascent fiber bundles in the first coagulation bath. The bundles are further formed and drawn in the second bath, and then enter the third bath for plasticizing and drawing. The bundles are then bundled and drawn into the post-processing process.

[0079] In the coagulation bath, the sulfuric acid concentration is 15 g / L, the sodium sulfate concentration is 65 g / L, the zinc sulfate concentration is 0.5 g / L, the reaction temperature is 32°C, and the stretching in the coagulation bath is controlled at -10%.

[0080] The sulfuric acid in the second bath is 40 g / L, the bath temperature is controlled at 40-50 ℃, and the stretching in the second bath is controlled at 80%.

[0081] The sulfuric acid concentration in the three baths is 10 g / L, the bath temperature is controlled at 97 ℃, and the stretching within the three baths is controlled at 12%.

[0082] The spinning speed in the first, second, and third coagulation baths is 30 m / min.

[0083] S6, Post-processing

[0084] After three baths of stretching, the fibers are washed, desulfurized, bleached, oiled, dried, and wound to obtain silica aerogel-based phase change temperature-controlled regenerated cellulose fibers.

[0085] Example 2: A method for preparing silica aerogel-based phase change temperature-controlled regenerated cellulose fiber, the preparation method comprising the following steps:

[0086] S1. Preparation of amino-modified silica aerogel

[0087] Tetraethyl orthosilicate, anhydrous ethanol, and deionized water were mixed and stirred until homogeneous. Nitric acid solution was added to adjust the pH to 2, and hydrolysis was carried out for 2 hours to form a sol. Ammonia solution was then added to adjust the pH to 6, and 3-aminopropyltrihydroxysilane was added to carry out a condensation reaction to form a wet gel. After aging, solvent replacement, and supercritical CO2, amino-modified silica aerogel was obtained with an average pore size of 27 nm and a porosity of 91%.

[0088] The molar ratio of tetraethyl orthosilicate, anhydrous ethanol, and deionized water is 1:12:4.

[0089] The concentration of the nitric acid solution is 0.5 mol / L, and the concentration of the ammonia solution is 0.1 mol / L.

[0090] The molar ratio of 3-aminopropyltrihydroxysilane to tetraethyl orthosilicate is 1:1.5.

[0091] The aging process was carried out at room temperature for 36 hours.

[0092] The solvent replacement was performed using n-hexane, with the solvent being replaced every 14 hours for a total of 3 times.

[0093] S2, Preparation of phase change material solutions

[0094] Phase change material, isophorone diisocyanate, and dibutyltin dilaurate were added to anhydrous n-hexane, heated to 60°C, and stirred for 60 min to dissolve, thus obtaining a phase change material solution.

[0095] The phase change material is n-octadecane and 48# paraffin, wherein the amount of 48# paraffin added is 5% of the mass of n-octadecane.

[0096] The mass ratio of the phase change material to anhydrous n-hexane is 1:4.

[0097] The mass ratio of the phase change material to the amino-modified silica aerogel in the phase change material solution is 1:1.

[0098] The molar ratio of isophorone diisocyanate in the phase change material solution to amino groups in the amino-modified silica aerogel is 0.4:1.

[0099] The amount of dibutyltin dilaurate added is 0.1% of the mass of isophorone diisocyanate.

[0100] S3, Vacuum Impregnation

[0101] Amino-modified silica aerogel was added to a reaction vessel, heated, stirred, and evacuated. Then, a phase change material solution was added, and the mixture was vacuum impregnated for 2 hours. After impregnation, the mixture was cooled at 15°C for 60 minutes and filtered to obtain a composite aerogel. The composite aerogel was then added to a surface reinforcing agent and impregnated for another 20 minutes before being filtered. The mixture was then kept at 40°C for 6 hours to obtain silica aerogel-based phase change energy storage microparticles.

[0102] The heating temperature is 60℃, the stirring speed is 200r / min, and the vacuum degree is -0.08MPa.

[0103] The surface enhancer contains isophorone diisocyanate at a concentration of 7 g / L, dibutyltin dilaurate at a concentration of 0.01 g / L, and anhydrous ethanol as the solvent.

[0104] Preferably, the ratio of the composite aerogel to the surface enhancer is 1:5.

[0105] S4. Preparation of blend spinning solution

[0106] Silica aerogel-based phase change energy storage microparticles and nonionic surfactants were added to deionized water and stirred to disperse them, thus obtaining a silica aerogel-based phase change energy storage microparticle dispersion.

[0107] Wood pulp with a degree of polymerization of 800 was selected and cellulose viscose solution was prepared by CS2 sulfonation process. Silica aerogel-based phase change energy storage microparticle dispersion was added to the cellulose viscose solution in proportion before spinning and mixed evenly to prepare a blend spinning solution.

[0108] The nonionic surfactant is Tween-80, and the amount added is 2% of the mass of the silica aerogel-based phase change energy storage microparticles.

[0109] The cellulose viscose solution has a viscosity of 80s (falling ball method), a maturity of 30mL (10% NH4Cl), a cellulose content of 6.8wt%, and a sodium hydroxide content of 5.6wt%.

[0110] The amount of silica aerogel-based phase change energy storage microparticle dispersion added is calculated as 20 wt% of the silica aerogel-based phase change energy storage microparticles in the cellulose viscose solution.

[0111] S5, spinning and forming

[0112] After the blended spinning solution is ejected from the spinneret, it is formed and drawn into nascent fiber bundles in the first coagulation bath. The bundles are further formed and drawn in the second bath, and then enter the third bath for plasticizing and drawing. The bundles are then bundled and drawn into the post-processing process.

[0113] In the coagulation bath, the sulfuric acid concentration is 20 g / L, the sodium sulfate concentration is 85 g / L, the zinc sulfate concentration is 0.1 g / L, the reaction temperature is 33°C, and the stretching in the coagulation bath is controlled at -20%.

[0114] The sulfuric acid concentration in the second bath is 50 g / L, the bath temperature is controlled at 50℃, and the stretching in the second bath is controlled at 70%.

[0115] The sulfuric acid concentration in the three baths is 15 g / L, the bath temperature is controlled at 100℃, and the stretching within the three baths is controlled at 10%.

[0116] The spinning speed in the first, second, and third coagulation baths is 35 m / min.

[0117] S6, Post-processing

[0118] After three baths of stretching, the fibers are washed, desulfurized, bleached, oiled, dried, and wound to obtain silica aerogel-based phase change temperature-controlled regenerated cellulose fibers.

[0119] Example 3: A method for preparing silica aerogel-based phase change temperature-controlled regenerated cellulose fiber, the preparation method comprising the following steps:

[0120] S1. Preparation of amino-modified silica aerogel

[0121] Tetraethyl orthosilicate, anhydrous ethanol, and deionized water were mixed and stirred until homogeneous. Nitric acid solution was added to adjust the pH to 4, and hydrolysis was carried out for 3 hours to form a sol. Ammonia solution was then added to adjust the pH to 7, and 3-aminopropyltrihydroxysilane was added to carry out a condensation reaction to form a wet gel. After aging, solvent replacement, and supercritical CO2, amino-modified silica aerogel was obtained with an average pore size of 21 nm and a porosity of 94%.

[0122] The molar ratio of tetraethyl orthosilicate, anhydrous ethanol, and deionized water is 1:12:4.

[0123] The concentration of the nitric acid solution is 1 mol / L, and the concentration of the ammonia solution is 0.2 mol / L.

[0124] The molar ratio of 3-aminopropyltrihydroxysilane to tetraethyl orthosilicate is 1:2.

[0125] The aging process was carried out at room temperature for 48 hours.

[0126] The solvent replacement was performed using n-hexane, with the solvent being replaced every 14 hours for a total of 4 replacements.

[0127] S2, Preparation of phase change material solutions

[0128] Phase change material, isophorone diisocyanate, and dibutyltin dilaurate were added to anhydrous n-hexane, heated to 63°C, and stirred for 50 minutes to dissolve, thus obtaining a phase change material solution.

[0129] The phase change material is n-octadecane and 48# paraffin, wherein the amount of 48# paraffin added is 10% of the mass of n-octadecane.

[0130] The mass ratio of the phase change material to anhydrous n-hexane is 1:4.

[0131] The mass ratio of the phase change material to the amino-modified silica aerogel in the phase change material solution is 1.5:1.

[0132] The molar ratio of isophorone diisocyanate in the phase change material solution to amino groups in the amino-modified silica aerogel is 0.5:1.

[0133] The amount of dibutyltin dilaurate added is 0.2% of the mass of isophorone diisocyanate.

[0134] S3, Vacuum Impregnation

[0135] Amino-modified silica aerogel was added to a reaction vessel, heated, stirred, and evacuated. Then, a phase change material solution was added, and the mixture was vacuum impregnated for 3 hours. After impregnation, the mixture was cooled at 10°C for 40 minutes and filtered to obtain a composite aerogel. The composite aerogel was then added to a surface reinforcing agent and impregnated for another 30 minutes before being filtered. The mixture was then kept at 50°C for 4 hours to obtain silica aerogel-based phase change energy storage microparticles.

[0136] The heating temperature is 70℃, the stirring speed is 300r / min, and the vacuum degree is -0.08MPa.

[0137] The surface enhancer contains isophorone diisocyanate at a concentration of 12 g / L, dibutyltin dilaurate at a concentration of 0.02 g / L, and anhydrous ethanol as the solvent.

[0138] The ratio of the composite aerogel to the surface enhancer is 1:3.

[0139] S4. Preparation of blend spinning solution

[0140] Silica aerogel-based phase change energy storage microparticles and nonionic surfactants were added to deionized water and stirred to disperse them, thus obtaining a silica aerogel-based phase change energy storage microparticle dispersion.

[0141] Wood pulp with a degree of polymerization of 1000 was selected and cellulose viscose solution was prepared by CS2 sulfonation process. Silica aerogel-based phase change energy storage microparticle dispersion was added to the cellulose viscose solution in proportion before spinning and mixed evenly to prepare a blended spinning solution.

[0142] The nonionic surfactant is Tween-80, and the amount added is 4% of the mass of the silica aerogel-based phase change energy storage microparticles.

[0143] The cellulose viscose solution has a viscosity of 90s (falling ball method), a maturity of 40mL (10% NH4Cl), a cellulose content of 8.0wt%, and a sodium hydroxide content of 7.2wt%.

[0144] The amount of silica aerogel-based phase change energy storage microparticle dispersion added is calculated as follows: the silica aerogel-based phase change energy storage microparticles in the silica aerogel-based phase change energy storage microparticle dispersion account for 25 wt% of the cellulose content in the cellulose viscose solution.

[0145] S5, spinning and forming

[0146] After the blended spinning solution is ejected from the spinneret, it is formed and drawn into nascent fiber bundles in the first coagulation bath. The bundles are further formed and drawn in the second bath, and then enter the third bath for plasticizing and drawing. The bundles are then bundled and drawn into the post-processing process.

[0147] In the coagulation bath, the sulfuric acid concentration is 18 g / L, the sodium sulfate concentration is 75 g / L, the zinc sulfate concentration is 0.4 g / L, the reaction temperature is 32°C, and the stretching in the coagulation bath is controlled at 0%.

[0148] The sulfuric acid concentration in the second bath is 45 g / L, the bath temperature is controlled at 45°C, and the stretching in the second bath is controlled at 70%.

[0149] The sulfuric acid concentration in the three baths is 13 g / L, the bath temperature is controlled at 100℃, and the stretching within the three baths is controlled at 8%.

[0150] The spinning speed in the first, second, and third coagulation baths is 33 m / min.

[0151] S6, Post-processing

[0152] After three baths of stretching, the fibers are washed, desulfurized, bleached, oiled, dried, and wound to obtain silica aerogel-based phase change temperature-controlled regenerated cellulose fibers.

[0153] Comparative Example 1: A representative example 1 was selected, in which isophorone diisocyanate and dibutyltin dilaurate were removed in S2, and the surface enhancer treatment in S3 was removed. All other aspects were the same as in Example 1, and this was used as Comparative Example 1.

[0154] Comparative Example 2: A representative example, Example 1, was selected. The surface reinforcing agent in S3 was removed, and the composite aerogel was directly treated with heat preservation. All other aspects were the same as in Example 1. This was used as Comparative Example 2.

[0155] Comparative Example 3: A representative example, Example 1, was selected, but the isophorone diisocyanate and dibutyltin dilaurate were removed from the phase change solution. All other components were the same as in Example 1. This was used as Comparative Example 3.

[0156] The fibers prepared in Examples 1-3 and Comparative Example 1 were subjected to performance testing, as detailed in Table 1.

[0157] Table 1

[0158] Testing items Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Fineness (dtex) 1.33 1.72 2.21 1.25 1.30 1.31 Dry fracture strength (cN / dtex) 2.61 2.44 2.3 2.15 2.26 2.22 Wet fracture strength (cN / dtex) 1.36 1.28 1.19 1.02 1.12 1.07 <![CDATA[△T max升 (℃)]]> 4.4 4.7 10.1 3.3 3.8 3.9 <![CDATA[△T max降 (℃)]]> 4.1 4.4 8.9 3.0 3.4 3.5 Enthalpy (J / g) 19.2 21.5 28.8 16.1 17.5 17.9 Enthalpy value (J / g) after 50 water washes 18.6 20.6 27.9 12.3 13.6 14.2 Loss rate of phase change material during fiber preparation (%) 0.5 0.8 0.6 16.2 8.5 6.8

[0159] From Table 1 and Figure 1-3 As can be seen, the regenerated cellulose fibers prepared using Examples 1-3 have good mechanical properties and excellent temperature control performance compared with ordinary viscose fibers, and the temperature control effect is long-lasting after 50 washes.

[0160] Compared with Example 1, after removing isophorone diisocyanate and dibutyltin dilaurate, the amino-modified silica aerogel had no cross-linking binding effect in the pores, the aerogel had poor strength and was not resistant to alkaline corrosion, and the internal phase change material was easily lost at high temperatures. Therefore, the fiber strength was slightly lower, the loss rate of phase change material was higher, and the water washing temperature control effect was slightly less durable.

[0161] In Comparative Example 2, after removing the surface reinforcing agent S2, the resulting silica aerogel-based phase change energy storage microparticles were slightly corroded in the viscose spinning solution, causing partial structural damage, resulting in the loss of a small amount of phase change material and a decrease in fiber mechanical properties.

[0162] In Comparative Example 3, isophorone diisocyanate and dibutyltin dilaurate were removed from the phase change solution. Crosslinking only occurred on the surface of the amino-modified silica aerogel. The structural brittleness of the aerogel remained unchanged, and the internal binding of the phase change material was insufficient, resulting in the loss of a small amount of phase change material.

[0163] Unless otherwise specified, all proportions and percentages mentioned in this invention are mass proportions and mass percentages; all raw materials are commercially available.

[0164] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for preparing silica aerogel-based phase change temperature-controlled regenerated cellulose fibers, characterized in that, The preparation method includes the preparation of amino-modified silica aerogel, the preparation of phase change material solution, vacuum impregnation, the preparation of blended spinning solution, spinning and post-treatment. The amino-modified silica aerogel is prepared by mixing tetraethyl orthosilicate, anhydrous ethanol and deionized water evenly, adding nitric acid solution to adjust the pH to 2-4, hydrolyzing for 2-3 hours to form a sol, adding ammonia solution to adjust the pH to 6-7, adding 3-aminopropyltrihydroxysilane to carry out a condensation reaction to form a wet gel, and then aging, solvent replacement and supercritical CO2 drying to obtain amino-modified silica aerogel. The phase change material solution is prepared by adding the phase change material, isophorone diisocyanate, and dibutyltin dilaurate into anhydrous n-hexane, heating to 60-65°C, and stirring for 50-60 minutes to dissolve the material to obtain the phase change material solution. The vacuum impregnation process involves adding amino-modified silica aerogel to a reaction vessel, heating, stirring, and evacuating the vessel, then adding a phase change material solution and impregnating under vacuum for 2–3 hours. After impregnation, the mixture is cooled at 10–15°C for 40–60 minutes and filtered to obtain a composite aerogel. The composite aerogel is then added to a surface reinforcing agent and impregnated for another 20–30 minutes before being filtered. The mixture is then kept at 40–50°C for 4–6 hours to obtain silica aerogel-based phase change energy storage microparticles. The phase change material is n-octadecane and paraffin, wherein the amount of paraffin added is 5-10% of the mass of n-octadecane; The mass ratio of phase change material to amino-modified silica aerogel in the phase change material solution is 1 to 1.5:

1. The molar ratio of isophorone diisocyanate in the phase change material solution to amino groups in the amino-modified silica aerogel is 0.4–0.5:

1. The amount of dibutyltin dilaurate added is 0.1-0.2% of the mass of isophorone diisocyanate; During the vacuum impregnation process, the heating temperature is 60-70℃, the stirring speed is 200-300 r / min, and the vacuum degree is ≤-0.08MPa; The surface enhancer contains isophorone diisocyanate at a concentration of 7–12 g / L, dibutyltin dilaurate at a concentration of 0.01–0.02 g / L, and anhydrous ethanol as the solvent. The ratio of the composite aerogel to the surface enhancer is 1:3 to 5.

2. The method for preparing silica aerogel-based phase change temperature-controlled regenerated cellulose fiber according to claim 1, characterized in that, The molar ratio of tetraethyl orthosilicate, anhydrous ethanol and deionized water is 1:12-15:4-6; The concentration of the nitric acid solution is 0.5–1 mol / L, and the concentration of the ammonia solution is 0.1–0.2 mol / L. The molar ratio of 3-aminopropyltrihydroxysilane to tetraethyl orthosilicate is 1:1.5 to 2.

3. The method for preparing silica aerogel-based phase change temperature-controlled regenerated cellulose fiber according to claim 1, characterized in that, The preparation of the blended spinning solution involves adding silica aerogel-based phase change energy storage microparticles and nonionic surfactants to deionized water and stirring to disperse them, thereby obtaining a silica aerogel-based phase change energy storage microparticle dispersion. A dissolving slurry with a degree of polymerization of 800-1000 was selected, and a cellulose viscose solution was prepared using the CS2 sulfonation process. A silica aerogel-based phase change energy storage microparticle dispersion was added to the cellulose viscose solution in proportion before spinning and mixed evenly to prepare a blended spinning solution.

4. The method for preparing silica aerogel-based phase change temperature-controlled regenerated cellulose fiber according to claim 3, characterized in that, The nonionic surfactant is one or more of Tween-80, Span-60, Span-80, and OP50, and the amount added is 2-4% of the mass of the silica aerogel-based phase change energy storage microparticles; The amount of silica aerogel-based phase change energy storage microparticle dispersion added is calculated as 18-25 wt% of the silica aerogel-based phase change energy storage microparticles in the cellulose viscose solution.

5. The method for preparing silica aerogel-based phase change temperature-controlled regenerated cellulose fiber according to claim 1, characterized in that, The spinning process involves the blended spinning solution being ejected from the spinneret and then formed and drawn into nascent fiber bundles in a coagulation bath. The fiber bundles are further formed and drawn in a second bath, and then enter a third bath for plasticizing and drawing. Finally, they are bundled and drawn into the post-processing stage.

6. The method for preparing silica aerogel-based phase change temperature-controlled regenerated cellulose fiber according to claim 5, characterized in that, In the coagulation bath, the sulfuric acid concentration is 15–20 g / L, the sodium sulfate concentration is 65–85 g / L, and the zinc sulfate concentration is 0.1–0.5 g / L. The reaction temperature is 31–33 °C, and the stretching within the coagulation bath is controlled between -20% and 0%. The sulfuric acid concentration in the second bath is 40–50 g / L, the bath temperature is controlled at 40–50 °C, and the stretching in the second bath is controlled at 60–80%. The sulfuric acid concentration in the three baths is 10–15 g / L, the bath temperature is controlled at 95–100℃, and the stretching within the three baths is controlled at 8–12%. The spinning speed in the first, second, and third coagulation baths is 30–35 m / min.

7. The method for preparing silica aerogel-based phase change temperature-controlled regenerated cellulose fiber according to claim 1, characterized in that, The post-processing involves washing, desulfurizing, bleaching, oiling, drying, and winding the fibers after three-bath stretching to obtain silica aerogel-based phase change temperature-controlled regenerated cellulose fibers.

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