Preparation method of alumina spinning gel

Abstract

The invention relates to a preparation method of alumina spinning gel, and belongs to the technical field of colloidal materials. According to the technical scheme, an inorganic aluminum source is adopted to replace a traditional organic aluminum source, and the reaction ratio of aluminum sulfate to sodium bicarbonate is controlled under a low-temperature condition, so that the alumina hydrate with high activity is synthesized; furthermore, the temperature, time and material proportion of carboxylation, polymerization and aging processes are accurately controlled, so that the aluminum carboxylate is self-polymerized to form high-viscosity high-polymerization-state aluminum carboxylate, and a thickening agent and a spinning auxiliary agent do not need to be additionally added, so that the process complexity is simplified while the alumina spinning gel performance is guaranteed, and the production cost is reduced. And finally, low-cost and high-performance preparation of the alumina spinning gel is realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of colloidal materials, and particularly relates to a preparation method of an alumina spinning gel. BACKGROUND

[0002] Continuous alumina fiber is a kind of high-performance inorganic non-metallic material, which has been widely used in many high-tech fields such as aviation, aerospace, weapons, automobiles and the like due to its high strength, low thermal conductivity, low thermal expansion coefficient, excellent heat resistance, high-temperature oxidation resistance, good thermal shock resistance and excellent corrosion resistance. At present, the representative methods for producing continuous alumina fiber at home and abroad mainly include a sol-gel method developed by 3M Company, a melting method developed by DuPont Company and a prepolymerization method developed by Sumitomo Chemical of Japan. Among them, except for the melting method, the sol-gel method and the prepolymerization method both need to prepare a spinning gel, which is a key link in the production process of continuous alumina fiber.

[0003] Specifically, the sol-gel method developed by 3M Company adopts basic organic aluminum as an aluminum source, and corn syrup or polyvinyl alcohol (PVA) with a molecular weight of more than 600,000 as a thickening agent to prepare a spinning gel. Although this method can prepare a spinning gel with excellent performance, the use of organic aluminum source and thickening agent increases the production cost, and the process is relatively complex. On the other hand, the prepolymerization method developed by Sumitomo Chemical uses organic metal aluminum as an aluminum source to form a metal coordination compound through coordination and hydrolysis polymerization, and then a linear structure spinning gel is obtained. However, this method also has problems of harsh process conditions and high production cost. SUMMARY

[0004] The present application provides a preparation method of an alumina spinning gel to solve the technical problem of how to develop an alumina spinning gel preparation scheme with low cost and simple process. The present application provides a preparation method of an alumina spinning gel, which comprises the following steps: mixing and stirring an aluminum sulfate solution and a sodium bicarbonate solution under the condition that the temperature is not higher than 40 DEG C to obtain a mixed slurry; filtering the mixed slurry to obtain an alumina hydrate filter cake; washing, drying and crushing the alumina hydrate filter cake in sequence to obtain an alumina hydrate powder; mixing the alumina hydrate powder with deionized water to obtain an alumina hydrate slurry; carboxylating the alumina hydrate slurry to obtain an alkali carboxylate aluminum solution; sequentially performing polymerization treatment and dehydration treatment on the alkali carboxylate aluminum solution to obtain a high-polymerization carboxylate aluminum; A stabilizer was added to the highly polymerized aluminum carboxylate and the mixture was aged to obtain an alumina spinning gel.

[0005] Optionally, in the mixed slurry, the molar ratio of aluminum sulfate to sodium bicarbonate is 0.05 to 0.08.

[0006] Optionally, the carboxylic acid used in the carboxylation treatment is at least one of citric acid, lactic acid, malic acid, tartaric acid, and acetic acid.

[0007] Optionally, the mass of the carboxylic acid is 40% to 240% of the mass of the alumina hydrate powder.

[0008] Optionally, the carboxylation treatment temperature is 60℃~85℃, and the carboxylation treatment time is ≥0.5h.

[0009] Optionally, the polymerization treatment temperature is ≥85℃, and the polymerization treatment time is 2h to 8h.

[0010] Optionally, the aging treatment temperature is 25℃~50℃, and the aging treatment time is 4h~8h.

[0011] Optionally, the volume of water used in a single washing process is more than 500% of the volume of the mixed slurry.

[0012] Optionally, the drying temperature is 90℃~95℃.

[0013] Optionally, the mass of the deionized water is 150% to 300% of the mass of the alumina hydrate powder.

[0014] Optionally, the stabilizer is at least one selected from citric acid, lactic acid, malic acid, tartaric acid, and acetic acid.

[0015] Optionally, the mass of the stabilizer is 0.1% to 1% of the mass of the alumina hydrate powder.

[0016] The technical solutions provided in this application have the following advantages compared with the prior art: This application provides a method for preparing alumina spinning gel. The method includes: mixing and stirring an aluminum sulfate solution and a sodium bicarbonate solution at a temperature not exceeding 40°C to obtain a mixed slurry; filtering the mixed slurry to obtain an alumina hydrate filter cake; sequentially washing, drying, and crushing the alumina hydrate filter cake to obtain alumina hydrate powder; mixing the alumina hydrate powder with deionized water to obtain an alumina hydrate slurry; subjecting the alumina hydrate slurry to carboxylate treatment to obtain a basic aluminum carboxylate solution; sequentially polymerizing and dehydrating the basic aluminum carboxylate solution to obtain a highly polymerized aluminum carboxylate; and adding a stabilizer to the highly polymerized aluminum carboxylate for aging treatment to obtain alumina spinning gel. By using an inorganic aluminum source (aluminum sulfate) instead of an organic aluminum source, and reacting the aluminum sulfate solution with the sodium bicarbonate solution to generate alumina hydrate, the use of expensive organic aluminum sources is avoided, significantly reducing raw material costs. By controlling the reaction ratio of aluminum sulfate and sodium bicarbonate under low-temperature conditions, the generated alumina hydrate is ensured to have high activity, providing a high-quality precursor for subsequent steps. A carboxylation treatment is introduced, using carboxylic acid to modify the alumina hydrate, forming a basic aluminum carboxylate solution. This step not only enhances the chemical stability of the aluminum source but also provides a good reaction basis for subsequent polymerization. Then, through polymerization and dehydration treatments, the basic aluminum carboxylate is converted into a highly polymerized aluminum carboxylate. This process does not require the addition of thickeners such as PVA; the polymerization viscosity of the highly polymerized aluminum carboxylate itself is sufficient to meet spinning requirements, simplifying the process. Finally, a stabilizer is added for aging treatment to adjust the viscosity and stability of the alumina spinning gel, making it suitable for dry spinning. Precise control of aging temperature and time ensures the uniformity and stability of the alumina spinning gel quality. Through the precise control of the above steps, a direct conversion from an inorganic aluminum source to a high-alumina-content spinning gel is achieved without the need for additional thickeners and spinning aids, significantly simplifying the process. Attached Figure Description

[0017] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0018] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic flowchart illustrating a method for preparing alumina spinning gel according to an embodiment of this application. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0021] The range descriptions used herein, such as numerical ranges and proportional ranges, include all possible sub-ranges and single numerical values ​​within that range. For example, the range descriptions of "1 to 6" or "1~6" cover all sub-ranges (such as 1 to 3, 2 to 5, etc.) and single numbers (such as 1, 2, 3, 4, 5, 6) between 1 and 6. Unless otherwise specified, the terms "including" and "contains" as used herein mean "including but not limited to"; relational terms such as "first" and "second" are used only to distinguish different entities or operations and do not imply an actual order or relationship; "and / or" indicates that multiple situations can exist individually or simultaneously; expressions such as "at least one," "multiple," and "at least one" refer to any combination of the corresponding objects, including combinations of single or multiple objects. The proportional relationships mentioned herein, such as mass ratios and molar ratios, should be understood as the correspondence between the first and second terms of a proportional formula, according to the order of description. The raw materials, reagents, instruments, and equipment used herein can all be obtained through commercial purchase or prepared using existing methods.

[0022] Figure 1 This is a schematic flowchart illustrating a method for preparing alumina spinning gel according to an embodiment of this application.

[0023] Please see Figure 1 This application provides a method for preparing alumina spinning gel, the method comprising: S1. Under conditions where the temperature does not exceed 40℃, aluminum sulfate solution and sodium bicarbonate solution are mixed and stirred to obtain a mixed slurry; S2. Filter the mixed slurry to obtain alumina hydrate filter cake; S3. The alumina hydrate filter cake is washed, dried and crushed in sequence to obtain alumina hydrate powder. S4. The alumina hydrate powder is mixed with deionized water to obtain an alumina hydrate slurry. S5. The alumina hydrate slurry is subjected to carboxylation treatment to obtain a basic aluminum carboxylate solution. S6. The basic aluminum carboxylate solution is subjected to polymerization and dehydration treatments in sequence to obtain highly polymerized aluminum carboxylate. S7. Add a stabilizer to the highly polymerized aluminum carboxylate and age it to obtain alumina spinning gel.

[0024] The method for preparing alumina spinning gel provided in this application is a technical solution that uses an inorganic aluminum source as the core and prepares high-performance spinning gel by precisely controlling process parameters. Its core advantage lies in abandoning the traditional organic aluminum source and additional spinning aids (such as PVA), and forming a high-viscosity system through the self-polymerization of aluminum carboxylate salt, thereby simplifying the process, reducing costs, and improving the performance of the final fiber product.

[0025] Carboxylation treatment involves mixing alumina hydrate slurry with carboxylic acids (such as citric acid and lactic acid) and reacting them at a specific temperature. This causes carboxylic acid molecules to adsorb onto the surface of the alumina hydrate, forming aluminum carboxylate salts. This step not only increases the activity of the alumina hydrate but also provides conditions for subsequent polymerization reactions. The aluminum carboxylate salts polymerize at high temperatures to form highly polymerized aluminum carboxylate. In this step, the intermolecular bonds of the aluminum carboxylate salt increase, forming a three-dimensional network structure, thus generating sufficient viscosity for spinning without the need for additional thickeners. Adding stabilizers (such as citric acid and lactic acid) to the highly polymerized aluminum carboxylate and aging it at a specific temperature further stabilizes its structure, which is beneficial for subsequent spinning and calcination processes. By implementing the technical solution of this application, the problems of high cost, complex process, and harsh conditions in the preparation of spinning gels during continuous alumina fiber production have been successfully solved, providing strong support for the large-scale production and application of alumina fibers.

[0026] In some embodiments, the ratio of the amount of aluminum sulfate to the amount of sodium bicarbonate in the mixed slurry is 0.05 to 0.08.

[0027] In the preparation of alumina spinning gel, aluminum sulfate and sodium bicarbonate are key raw materials. They react chemically to form alumina hydrate, which is the basis for subsequent alumina spinning gel preparation. Setting the molar ratio of aluminum sulfate to sodium bicarbonate in the slurry to 0.05–0.08 helps maintain the slurry within a suitable pH range, ensuring the effective formation of alumina hydrate. When the molar ratio of aluminum sulfate to sodium bicarbonate is below 0.05, the pH value of the slurry will be relatively high, which may cause the alumina hydrate to undergo a crystal phase transformation and become deactivated, thus affecting the formation of alumina hydrate and the subsequent processing effect. Conversely, when the molar ratio of aluminum sulfate to sodium bicarbonate is above 0.08, the pH value of the slurry will be relatively low, which may hinder the complete hydrolysis and precipitation of aluminum ions, resulting in the inability to form the target alumina hydrate, thereby affecting the quality and performance of the alumina spinning gel.

[0028] In some embodiments, the volume of water used in a single washing process is more than 500% of the volume of the mixed slurry.

[0029] The main purpose of the washing process is to remove impurities from the alumina hydrate filter cake, especially soluble salts such as sodium sulfate. If these impurities remain in the alumina hydrate filter cake, they will affect subsequent carboxylation treatments, polymerization reactions, and ultimately the quality and performance of the final alumina spinning gel. Using a sufficient amount of washing water ensures that impurities are fully dissolved and carried away, thereby improving the purity of the alumina hydrate. In this embodiment, the volume of water used in a single washing process should not be less than 500% of the volume of the mixed slurry. This means that if the volume of the mixed slurry is 1 liter, then the amount of water used in a single washing should be at least 5 liters. This water volume ensures the washing effect and reduces impurity residue. If the volume of water used in a single washing is less than 500% of the volume of the mixed slurry, it will result in excessive impurity residue, affecting subsequent reactions and the quality of the alumina spinning gel. For example, excessive sulfate ion residue will reduce the degree of polymerization during the polymerization stage, resulting in a low molecular weight of highly polymerized aluminum carboxylate, thus affecting the spinning effect of the alumina spinning gel.

[0030] In some embodiments, the drying temperature is 90°C to 95°C.

[0031] Drying is a crucial step in the preparation of alumina hydrate powder. Its purpose is to remove moisture from the alumina hydrate filter cake, facilitating subsequent crushing, sieving, and carboxylation processes. A drying temperature of 90℃ to 95℃ effectively evaporates moisture from the alumina hydrate filter cake while preventing excessive temperature from causing agglomeration or altering the properties of the alumina hydrate powder. Furthermore, the activity of alumina hydrate significantly impacts subsequent carboxylation and polymerization reactions. Excessively high drying temperatures may lead to alumina hydrate deactivation, affecting its reactivity. Maintaining the drying temperature within the 90℃ to 95℃ range ensures that the alumina hydrate retains a certain level of activity, providing favorable conditions for subsequent reactions. 90℃ to 95℃ is a temperature range that is relatively easy to control and maintain in practice. Most drying equipment can precisely operate within this temperature range, ensuring the stability and consistency of the drying effect.

[0032] In some embodiments, the mass of the deionized water is 150% to 300% of the mass of the alumina hydrate powder.

[0033] The main function of deionized water is to mix with alumina hydrate powder to form a homogeneous alumina hydrate slurry. The mass of deionized water should be 150%–300% of the mass of the alumina hydrate powder to ensure sufficient wetting and dispersion, thus forming a stable slurry system. If the mass of deionized water is less than 150% of the mass of the alumina hydrate powder, the powder may not be completely slurried, leading to agglomeration or precipitation, affecting subsequent carboxylation and polymerization reactions. The mass of deionized water also directly affects the viscosity of the alumina hydrate slurry. Appropriate viscosity is crucial for subsequent pumping, mixing, and reaction processes. If the viscosity of the alumina hydrate slurry is too high, it may cause pumping difficulties and uneven mixing; if the viscosity is too low, it may affect reaction efficiency. A deionized water mass of 150%–300% of the mass of the alumina hydrate powder helps control the viscosity of the alumina hydrate slurry within a suitable range. Finally, while the amount of deionized water needs to be sufficient for proper slurry preparation, excessive water can also cause problems. If the amount of deionized water exceeds 300% of the mass of alumina hydrate powder, more water needs to be removed in subsequent polymerization stages. This not only increases energy consumption but may also affect the efficiency of the polymerization reaction and the performance of the product.

[0034] In some embodiments, the carboxylic acid used in the carboxylation treatment is at least one of citric acid, lactic acid, malic acid, tartaric acid, and acetic acid.

[0035] The main purpose of carboxylation is to form a basic aluminum carboxylate solution through the reaction of carboxylic acid with alumina hydrate. This step is crucial for the successful execution of subsequent polymerization reactions and the optimization of alumina spinning gel properties. In carboxylation, at least one of citric acid, lactic acid, malic acid, tartaric acid, and acetic acid can be selected.

[0036] In some embodiments, the mass of the carboxylic acid is 40% to 240% of the mass of the alumina hydrate powder.

[0037] The quality of carboxylic acid needs to be controlled within a certain range to ensure the sufficiency of the carboxylation reaction. If the carboxylic acid quality is too low (below 40% of the alumina hydrate powder mass), the carboxylation reaction may be incomplete, and the residual alumina hydrate powder will affect the subsequent polymerization process, thus affecting the performance of the alumina spinning gel. On the other hand, if the carboxylic acid quality is too high (exceeding 240% of the alumina hydrate powder mass), the alumina hydrate powder may be over-converted into aluminum carboxylate salts, making the subsequent polymerization process difficult, or the resulting highly polymerized aluminum carboxylate may have an excessively wide molecular weight distribution, affecting the spinning effect of the alumina spinning gel. Over-reaction may also lead to increased production costs because more carboxylic acid raw materials are required.

[0038] In some embodiments, the carboxylation treatment is performed at a temperature of 60°C to 85°C for a duration of ≥0.5 h.

[0039] In the preparation of alumina spinning gel, carboxylation primarily converts alumina hydrate into a basic aluminum carboxylate solution, providing a reactive intermediate for subsequent polymerization steps. Within a temperature range of 60℃ to 85℃, the reactivity of carboxylic acids and alumina hydrate is high, facilitating the effective reaction of carboxylic acid molecules with alumina hydrate to form a stable basic aluminum carboxylate structure. Temperatures below 60℃ may slow the reaction rate or even prevent complete carboxylation; temperatures above 85℃ may cause partial decomposition of the carboxylic acid or other side reactions, affecting the quality of the basic aluminum carboxylate solution. An appropriate temperature range also contributes to the formation of a stable basic aluminum carboxylate solution. Within this range, the reaction products are less prone to decomposition or deterioration, ensuring the smooth progress of subsequent polymerization and dehydration processes. The 60℃–85℃ temperature range is relatively easy to control and has high feasibility in industrial production. Precise temperature control can achieve stability and repeatability of the carboxylation process, improving production efficiency and product quality.

[0040] In practice, the following measures can be taken to ensure that the carboxylation treatment temperature is between 60℃ and 85℃: Use temperature-controlled equipment, such as a constant temperature water bath or oil bath, to maintain the temperature stability of the reaction system through heating and circulation systems.

[0041] Real-time monitoring and adjustment: During the carboxylation process, a temperature sensor is used to monitor the temperature of the reaction system in real time, and the heating power or cooling rate is adjusted as needed to keep the temperature within the set range.

[0042] The carboxylation process requires sufficient time to ensure that the carboxylic acid reacts fully with the alumina hydrate to generate enough basic aluminum carboxylate. If the carboxylation time is less than 0.5 hours, the reaction between the carboxylic acid and the alumina hydrate may be incomplete, resulting in some alumina hydrate remaining uncarboxylated. This will affect the formation of highly polymerized aluminum carboxylate in subsequent polymerization steps, and consequently, the performance of the alumina spinning gel.

[0043] In practice, the reaction time for carboxylation can be determined by monitoring the reaction progress (such as pH changes and solution viscosity). Once the carboxylation reaction reaches the desired level, it can be stopped to avoid unnecessary energy consumption and time waste. The temperature and time of the carboxylation treatment need to be controlled in a coordinated manner to obtain the optimal basic aluminum carboxylate solution. Appropriate temperature and sufficient time can ensure that the reaction proceeds smoothly and produces high-quality basic aluminum carboxylate.

[0044] In some embodiments, the polymerization treatment temperature is ≥85°C, and the polymerization treatment time is 2h to 8h.

[0045] In the preparation method of alumina spinning gel, the main role of polymerization treatment is to convert basic aluminum carboxylate into highly polymerized aluminum carboxylate, achieving a molecular weight of over 1 million. This eliminates the need for additional spinning aids such as PVA and corn syrup, simplifying the process, reducing production costs, and decreasing degassing and glue removal during subsequent calcination, thereby improving the density and spinning effect of continuous alumina fibers. At temperatures ≥85℃, basic aluminum carboxylate molecules can acquire sufficient energy to interconnect, forming long-chain or network-structured polymers. Below 85℃, molecular motion slows down, making effective polymerization difficult. By controlling the polymerization treatment temperature at 85℃ or higher, the basic aluminum carboxylate molecules can be fully polymerized to form an alumina spinning gel with sufficient molecular weight and viscosity. This alumina spinning gel maintains a stable morphology during subsequent spinning and ultimately transforms into high-performance continuous alumina fibers.

[0046] The duration of polymerization treatment directly affects the molecular weight and structure of highly polymerized aluminum carboxylate. Treatment times shorter than 2 hours may result in incomplete polymerization, leading to insufficient molecular weight of the highly polymerized aluminum carboxylate and affecting the performance of the alumina spinning gel. Treatment times longer than 8 hours may cause over-polymerization of the highly polymerized aluminum carboxylate molecular chains, forming an overly viscous or excessively cross-linked alumina spinning gel, which is also detrimental to the spinning process. By controlling the polymerization treatment time between 2 and 8 hours, the molecular weight and structure of the highly polymerized aluminum carboxylate can be optimized. The optimized highly polymerized aluminum carboxylate possesses sufficient viscosity to support the spinning process without being too viscous to be difficult to handle. Furthermore, the optimized alumina spinning gel can reduce degassing and glue removal during calcination, improving the density of continuous alumina fibers and thus ensuring the performance of continuous alumina fibers.

[0047] In some embodiments, the stabilizer is at least one selected from citric acid, lactic acid, malic acid, tartaric acid, and acetic acid.

[0048] In the preparation of alumina spinning gel, stabilizers can maintain the stability and uniformity of the alumina spinning gel structure during its formation and aging process, preventing precipitation or stratification, thereby ensuring the quality and performance of the alumina spinning gel. In the embodiments of this application, the stabilizer can be at least one selected from citric acid, lactic acid, malic acid, tartaric acid, and acetic acid. These organic acids have the following advantages as stabilizers: Forming stable complexes with aluminum ions: The carboxyl groups (-COOH) in these organic acid molecules can react with aluminum ions (Al). 3+A complexation reaction occurs, forming a stable complex, thereby enhancing the structural stability of the alumina spinning gel.

[0049] Adjusting the pH value of the system: Organic acids, as weak acids, can adjust the pH value of the alumina spinning gel system to a certain extent, keeping the alumina spinning gel system within a suitable pH range, which is conducive to the formation and stability of alumina spinning gel.

[0050] Improving the processing properties of alumina spinning gel: By adding an appropriate amount of organic acid as a stabilizer, the flowability and spinnability of alumina spinning gel can be improved, making it easier for alumina spinning gel to undergo subsequent spinning processes.

[0051] In some embodiments, the mass of the stabilizer is 0.1% to 1% of the mass of the alumina hydrate powder.

[0052] In the preparation of alumina spinning gel, stabilizers can form a stable structure in highly polymerized aluminum carboxylate, preventing the breakage of its polymeric bonds and thus ensuring the quality and performance of the alumina spinning gel. If the stabilizer mass is less than 0.1% of the alumina hydrate powder mass, a stable polymeric structure may not be effectively formed. During aging, the polymeric bonds of the highly polymerized aluminum carboxylate are prone to breakage, leading to a decline in the performance of the alumina spinning gel, specifically manifested as easy breakage of the alumina spinning gel during spinning and localized damage to the fiber preform. If the stabilizer mass exceeds 1% of the alumina hydrate powder mass, the pH value of the alumina spinning gel system may decrease, thereby disrupting the stability of the polymeric bonds of the highly polymerized aluminum carboxylate, leading to bond breakage, and consequently affecting the quality and spinning effect of the alumina spinning gel. Finally, in practical applications, cost-effectiveness needs to be considered when selecting the stabilizer mass. Excessive stabilizer addition will increase production costs, while excessively low addition may not achieve the expected stabilization effect. A stabilizer mass of 0.1% to 1% of the alumina hydrate powder mass is an economical and effective choice.

[0053] In some embodiments, the aging treatment temperature is 25°C to 50°C, and the aging treatment time is 4 hours to 8 hours.

[0054] Aging treatment allows for full diffusion and interaction of the components in the alumina spinning gel system, achieving a more uniform and stable state. This prevents fiber breakage or performance inconsistencies caused by localized compositional or structural differences during subsequent spinning. Within a temperature range of 25℃ to 50℃, alumina spinning gel molecules gain sufficient energy for ordered arrangement and structural adjustment, resulting in a more stable and uniform alumina spinning gel network. This temperature range is neither too high, causing excessive molecular movement and structural damage, nor too low, preventing insufficient molecular movement and the formation of a stable structure. During aging, some slow chemical reactions or physical changes may occur within the alumina spinning gel. The 25℃–50℃ temperature range allows for control of these reaction rates, ensuring they complete within a reasonable timeframe, thus yielding a high-performance alumina spinning gel. Aging within this range also improves production efficiency while maintaining alumina spinning gel quality, as this temperature range is relatively easy to control and does not require excessive energy consumption. If the aging temperature is below 25°C, the movement of alumina spinning gel molecules will be restricted, leading to an unstable alumina spinning gel structure and decreased performance. Simultaneously, low temperatures may prolong the aging time, reducing production efficiency. If the aging temperature is above 50°C, alumina spinning gel molecules may gain excessive energy and undergo excessive movement, resulting in structural damage or unstable performance. Furthermore, high temperatures may trigger unwanted side reactions, affecting the purity of the alumina spinning gel.

[0055] Besides temperature, aging time is also a crucial factor affecting the performance of alumina spinning gel. Within the temperature range of 25℃ to 50℃, a suitable aging time needs to be determined to ensure the stabilization of the alumina spinning gel structure and the optimization of its performance. An aging time of 4 to 8 hours ensures sufficient cross-linking and stabilization of molecules in the alumina spinning gel system, thereby improving the mechanical properties and thermal stability of the alumina spinning gel. An aging time of less than 4 hours may lead to poor uniformity of the alumina spinning gel system, resulting in localized damage or breakage of the fiber preform after spinning; an aging time of more than 8 hours may cause the breakage of the polymer bonds in the highly polymerized aluminum carboxylate, similarly affecting the performance of the alumina spinning gel.

[0056] Example 1 At 35°C, aluminum sulfate solution and sodium bicarbonate solution were mixed and stirred, with the molar ratio of aluminum sulfate to sodium bicarbonate controlled at 0.06. The mixture was reacted for 30 minutes to obtain a slurry.

[0057] The mixed slurry is filtered to obtain an alumina hydrate filter cake. The filter cake is washed with deionized water, with a single wash volume of 600% of the mixed slurry volume, to ensure the removal of impurities such as sodium sulfate.

[0058] The washed filter cake was dried at 92°C for 4 hours, then crushed and sieved (200 mesh) to obtain highly active alumina hydrate powder.

[0059] Take 100 g of alumina hydrate powder and mix it with 200 g of deionized water (200% of the powder mass). Stir mechanically for 30 minutes to form a uniform alumina hydrate slurry.

[0060] Add 100 g of citric acid (100% of the powder mass) to the slurry and stir at 70°C for 1 hour to obtain a clear basic aluminum carboxylate solution.

[0061] The basic aluminum carboxylate solution was polymerized at 90°C for 4 hours, and then excess water was removed by dehydration under reduced pressure to obtain high-viscosity, highly polymerized aluminum carboxylate.

[0062] Add 0.5 g of citric acid as a stabilizer (0.5% of the powder mass) to highly polymerized aluminum carboxylate and age at 35°C for 6 hours to obtain a uniform and stable alumina spinning gel.

[0063] Example 2 At 30°C, aluminum sulfate solution and sodium bicarbonate solution were mixed and stirred, with the molar ratio of aluminum sulfate to sodium bicarbonate controlled at 0.07. The mixture was reacted for 30 minutes to obtain a slurry.

[0064] The mixed slurry is filtered to obtain an alumina hydrate filter cake. The filter cake is washed with deionized water, with a single wash volume of 600% of the mixed slurry volume, to ensure the removal of impurities such as sodium sulfate.

[0065] The washed filter cake was dried at 90°C for 4 hours, then crushed and sieved (200 mesh) to obtain highly active alumina hydrate powder.

[0066] Take 100 g of alumina hydrate powder and mix it with 200 g of deionized water (200% of the powder mass). Stir mechanically for 30 minutes to form a uniform alumina hydrate slurry.

[0067] Add 120 g of lactic acid (120% of the powder mass) to the slurry and stir at 80°C for 1 hour to obtain a clear basic aluminum carboxylate solution.

[0068] The basic aluminum carboxylate solution was polymerized at 95°C for 4 hours, and then excess water was removed by dehydration under reduced pressure to obtain high-viscosity, highly polymerized aluminum carboxylate.

[0069] Add 0.5 g of citric acid as a stabilizer (0.5% of the powder mass) to highly polymerized aluminum carboxylate and age at 30°C for 7 hours to obtain a uniform and stable alumina spinning gel.

[0070] Example 3 At 25°C, aluminum sulfate solution and sodium bicarbonate solution were mixed and stirred, with the molar ratio of aluminum sulfate to sodium bicarbonate controlled at 0.05. The mixture was reacted for 30 minutes to obtain a slurry.

[0071] The mixed slurry is filtered to obtain an alumina hydrate filter cake. The filter cake is washed with deionized water, with a single wash volume of 700% of the mixed slurry volume, to ensure the removal of impurities such as sodium sulfate.

[0072] The washed filter cake was dried at 90°C for 4 hours, then crushed and sieved (200 mesh) to obtain highly active alumina hydrate powder.

[0073] Take 100 g of alumina hydrate powder and mix it with 200 g of deionized water (200% of the powder mass). Stir mechanically for 30 minutes to form a uniform alumina hydrate slurry.

[0074] Add 80 g of acetic acid (120% of the powder mass) to the slurry and stir at 70°C for 1 hour to obtain a clear basic aluminum carboxylate solution.

[0075] The basic aluminum carboxylate solution was polymerized at 95°C for 6 hours, and then excess water was removed by dehydration under reduced pressure to obtain high-viscosity, highly polymerized aluminum carboxylate.

[0076] Add 0.5 g of citric acid as a stabilizer (0.5% of the powder mass) to highly polymerized aluminum carboxylate and age at 25°C for 8 hours to obtain a uniform and stable alumina spinning gel.

[0077] Comparative Example 1 At 35°C, aluminum sulfate solution and sodium bicarbonate solution were mixed and stirred, with the molar ratio of aluminum sulfate to sodium bicarbonate controlled at 0.06. The mixture was reacted for 30 minutes to obtain a slurry.

[0078] The mixed slurry is filtered to obtain an alumina hydrate filter cake. The filter cake is washed with deionized water, with a single wash volume of 600% of the mixed slurry volume, to ensure the removal of impurities such as sodium sulfate.

[0079] The washed filter cake was dried at 100°C for 4 hours, then crushed and sieved (200 mesh) to obtain highly active alumina hydrate powder.

[0080] Take 100 g of alumina hydrate powder and mix it with 200 g of deionized water (200% of the powder mass). Stir mechanically for 30 minutes to form a uniform alumina hydrate slurry.

[0081] Add 100 g of citric acid (100% of the powder mass) to the slurry and stir at 70°C for 1 hour to obtain a basic aluminum carboxylate solution.

[0082] The basic aluminum carboxylate solution was polymerized at 90°C for 4 hours, and then excess water was removed by dehydration under reduced pressure to obtain polymerized aluminum carboxylate.

[0083] Add 0.5 g of citric acid as a stabilizer (0.5% of the powder mass) to highly polymerized aluminum carboxylate and age at 35°C for 6 hours to obtain alumina spinning gel.

[0084] Comparative Example 2 At 35°C, aluminum sulfate solution and sodium bicarbonate solution were mixed and stirred, with the molar ratio of aluminum sulfate to sodium bicarbonate controlled at 0.06. The mixture was reacted for 30 minutes to obtain a slurry.

[0085] The mixed slurry is filtered to obtain an alumina hydrate filter cake. The filter cake is washed with deionized water, with a single wash volume of 600% of the mixed slurry volume, to ensure the removal of impurities such as sodium sulfate.

[0086] The washed filter cake was dried at 90°C for 4 hours, then crushed and sieved (200 mesh) to obtain highly active alumina hydrate powder.

[0087] Take 100 g of alumina hydrate powder and mix it with 200 g of deionized water (200% of the powder mass). Stir mechanically for 30 minutes to form a uniform alumina hydrate slurry.

[0088] Add 100 g of citric acid (100% of the powder mass) to the slurry and stir at 70°C for 1 hour to obtain a basic aluminum carboxylate solution.

[0089] The basic aluminum carboxylate solution was polymerized at 80°C for 4 hours, and then excess water was removed by dehydration under reduced pressure to obtain polymerized aluminum carboxylate.

[0090] Add 0.5 g of citric acid as a stabilizer (0.5% of the powder mass) to highly polymerized aluminum carboxylate and age at 35°C for 6 hours to obtain alumina spinning gel.

[0091] Comparative Example 3 At 35°C, aluminum sulfate solution and sodium bicarbonate solution were mixed and stirred, with the molar ratio of aluminum sulfate to sodium bicarbonate controlled at 0.06. The mixture was reacted for 30 minutes to obtain a slurry.

[0092] The mixed slurry is filtered to obtain an alumina hydrate filter cake. The filter cake is washed with deionized water, with a single wash volume of 600% of the mixed slurry volume, to ensure the removal of impurities such as sodium sulfate.

[0093] The washed filter cake was dried at 90°C for 4 hours, then crushed and sieved (200 mesh) to obtain highly active alumina hydrate powder.

[0094] Take 100 g of alumina hydrate powder and mix it with 200 g of deionized water (200% of the powder mass). Stir mechanically for 30 minutes to form a uniform alumina hydrate slurry.

[0095] Add 30 g of citric acid (30% of the powder mass) to the slurry and stir at 70°C for 1 hour to obtain a basic aluminum carboxylate solution.

[0096] The basic aluminum carboxylate solution was polymerized at 90°C for 4 hours, and then excess water was removed by dehydration under reduced pressure to obtain polymerized aluminum carboxylate.

[0097] Add 0.5 g of citric acid as a stabilizer (0.5% of the powder mass) to highly polymerized aluminum carboxylate and age at 35°C for 6 hours to obtain alumina spinning gel.

[0098] Comparative Example 4 At 35°C, aluminum sulfate solution and sodium bicarbonate solution were mixed and stirred, with the molar ratio of aluminum sulfate to sodium bicarbonate controlled at 0.06. The mixture was reacted for 30 minutes to obtain a slurry.

[0099] The mixed slurry is filtered to obtain an alumina hydrate filter cake. The filter cake is washed with deionized water, with a single wash volume of 600% of the mixed slurry volume, to ensure the removal of impurities such as sodium sulfate.

[0100] The washed filter cake was dried at 90°C for 4 hours, then crushed and sieved (200 mesh) to obtain highly active alumina hydrate powder.

[0101] Take 100 g of alumina hydrate powder and mix it with 200 g of deionized water (200% of the powder mass). Stir mechanically for 30 minutes to form a uniform alumina hydrate slurry.

[0102] Add 100 g of citric acid (100% of the powder mass) to the slurry and stir at 70°C for 1 hour to obtain a basic aluminum carboxylate solution.

[0103] The basic aluminum carboxylate solution was polymerized at 99°C for 1 hour, and then excess water was removed by dehydration under reduced pressure to obtain polymerized aluminum carboxylate.

[0104] Add 0.5 g of citric acid as a stabilizer (0.5% of the powder mass) to highly polymerized aluminum carboxylate and age at 35°C for 6 hours to obtain alumina spinning gel.

[0105] The alumina spinning gels obtained in Examples 1-3 and Comparative Examples 1-4 were tested, and the results are shown in Table 1.

[0106] Table 1

[0107] As shown in Table 1, the alumina spinning gel obtained by the preparation method provided by this invention can achieve an alumina content of over 28%, meeting the requirements for the preparation of continuous alumina ceramic fibers with high alumina content. The alumina spinning gels prepared in Examples 1-3 exhibit good spinning performance; the manually drawn fiber length can exceed 10 meters without breakage, making them suitable for dry spinning processes and capable of producing long fibers without breakage. SEM testing of the alumina fibers after calcination of the alumina spinning gels prepared in Examples 1-3 shows that the primary crystal size is between 100-300 nm. This fine grain structure helps to improve the fiber's strength and heat resistance.

[0108] Furthermore, one or more technical solutions in the embodiments of the present invention have at least the following technical effects or advantages: Cost-effectiveness: The method provided in this embodiment of the invention uses an inorganic aluminum source instead of a traditional organic aluminum source, which reduces the cost of raw materials.

[0109] Simplified process: The embodiments of the present invention do not introduce additional thickeners and spinning aids, thus simplifying the process flow.

[0110] Performance Improvement: By precisely controlling the reaction conditions, the alumina spinning gel prepared in this embodiment of the invention has a high alumina content and good fiber density.

[0111] Environmentally friendly: The method provided in this embodiment of the invention transforms the traditional organic aluminum source system into an inorganic aluminum source. It relies on the viscosity of aluminum carboxylate polymerization to replace spinning aids such as PVA, PVP, and PEO. The calcination process can effectively reduce the amount of exhaust gas and glue, which is beneficial to environmental protection.

[0112] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed in this application.

Claims

1. A method for preparing an alumina spinning gel, characterized in that, The method includes: Under conditions where the temperature does not exceed 40℃, aluminum sulfate solution and sodium bicarbonate solution are mixed and stirred to obtain a mixed slurry; The mixture slurry was filtered to obtain an alumina hydrate filter cake; The alumina hydrate filter cake was washed, dried and crushed in sequence to obtain alumina hydrate powder. The alumina hydrate powder is mixed with deionized water to obtain an alumina hydrate slurry. The alumina hydrate slurry was subjected to carboxylation treatment to obtain a basic aluminum carboxylate solution. The basic aluminum carboxylate solution was subjected to polymerization and dehydration treatments in sequence to obtain highly polymerized aluminum carboxylate. A stabilizer was added to the highly polymerized aluminum carboxylate and the mixture was aged to obtain an alumina spinning gel.

2. The method according to claim 1, characterized in that, In the mixed slurry, the molar ratio of aluminum sulfate to sodium bicarbonate is 0.05 to 0.

08.

3. The method according to claim 1, characterized in that, The carboxylic acid used in the carboxylation treatment is at least one of citric acid, lactic acid, malic acid, tartaric acid, and acetic acid.

4. The method according to claim 3, characterized in that, The mass of the carboxylic acid is 40% to 240% of the mass of the alumina hydrate powder.

5. The method according to claim 3, characterized in that, The carboxylation treatment is performed at a temperature of 60℃ to 85℃ for a duration of ≥0.5h.

6. The method according to claim 1, characterized in that, The polymerization treatment temperature is ≥85℃, and the polymerization treatment time is 2h to 8h.

7. The method according to claim 1, characterized in that, The aging process is carried out at a temperature of 25°C to 50°C for 4 hours to 8 hours.

8. The method according to claim 1, characterized in that, The volume of water used in a single washing process is more than 500% of the volume of the mixed slurry, and / or; The drying temperature is 90℃~95℃.

9. The method according to claim 1, characterized in that, The mass of the deionized water is 150% to 300% of the mass of the alumina hydrate powder.

10. The method according to claim 1, characterized in that, The stabilizer is at least one of citric acid, lactic acid, malic acid, tartaric acid, and acetic acid, and / or; The mass of the stabilizer is 0.1% to 1% of the mass of the alumina hydrate powder.

Images