Preparation method of instant sodium carboxymethyl cellulose

Abstract

The invention discloses a preparation method of instant sodium carboxymethyl cellulose, which belongs to the technical field of high polymer material modification, and comprises the following steps: firstly, preparing sodium carboxymethyl cellulose basic powder by taking refined cotton as a raw material by adopting a conventional alkalization etherification process; the core of the material is that an inorganic heterostructure material is adopted for modification, the material takes a zinc oxide nanorod synthesized by a hydrothermal method as a template, a silicon dioxide shell layer is coated through tetraethoxysilane hydrolysis, a fluoride buffer solution is utilized for controllable etching to construct gradient mesopores, and then temperature programming calcination is performed to prepare the material. A trace amount of the modified material is dispersed and then sprayed to the surface of sodium carboxymethyl cellulose basic powder, and a final product is obtained through low-temperature drying. By introducing the modifier with a gradient mesoporous structure, on the premise of not changing the main chemical structure of the sodium carboxymethyl cellulose, the surface gel barrier in the dissolution process of the sodium carboxymethyl cellulose is remarkably destroyed, so that the rapid dissolution of the product is realized, and meanwhile, the whole modification process is simple and efficient, and is suitable for large-scale production.

Description

Technical Field

[0001] This invention relates to the field of polymer materials and inorganic nanocomposite materials, specifically to a method for preparing fast-dissolving sodium carboxymethyl cellulose. Background Technology

[0002] Sodium carboxymethyl cellulose (CMC), as a crucial water-soluble cellulose ether derivative, is widely and deeply applied in key fields such as the food industry, daily chemical industry, pharmaceutical industry, ceramic manufacturing, and the rapidly developing new energy battery industry, due to its excellent thickening, film-forming, binding, moisture retention, and biocompatibility properties. Particularly in lithium-ion battery manufacturing, it serves as a core binder and thickener in aqueous electrode slurries, and its performance directly affects the uniformity of electrode coating, the stability of the slurry, and the final electrochemical performance of the battery. Traditionally, CMC is mainly prepared by etherification of cellulose raw materials with chloroacetic acid or its salts under alkaline conditions. Although this process is mature, the conventional products obtained have significant inherent defects in solubility. Upon contact with water, the surface of these products rapidly hydrates, forming a dense, high-viscosity gel layer. This gel layer severely hinders further water penetration into the particle interior, resulting in complete dissolution requiring several hours, and easily forming difficult-to-disperse "fish-eye" shaped clumps during the process. This slow dissolution rate not only significantly reduces production and mixing efficiency and increases energy consumption, but also becomes a prominent bottleneck restricting production efficiency and product consistency in application scenarios with extremely high requirements for process timeliness, such as the production of battery electrodes that require rapid slurry preparation.

[0003] To overcome the poor solubility of sodium carboxymethyl cellulose (CMC), various physical and chemical modification approaches have been proposed by the industry and research fields. Physical methods mainly involve special puffing treatments of the finished powder, such as freeze-drying or instantaneous high-temperature treatment, aiming to increase the porosity and specific surface area of ​​the particles, thereby accelerating the initial hydration rate. Chemical methods focus on optimizing synthesis process parameters, such as exploring different catalysts, controlling the solvent composition of the reaction system, adjusting the order and temperature curves of alkalization and etherification, and even attempting graft copolymerization with other polymers to increase the degree of substitution or change its hydrophilic-lipophilic balance. However, these existing technologies all have their limitations. Physical puffing methods often have specific equipment requirements, and the treated products are prone to rehydration and clumping during storage, resulting in unstable solubility. While complex chemical modifications may improve solubility to some extent, they are often accompanied by increased side reactions, decreased product purity, wider molecular weight distribution, or adverse changes in inherent viscosity. They may even introduce chemicals that do not comply with safety regulations, limiting their application in sensitive fields such as food or medicine. More importantly, most of these methods fail to fundamentally overcome the core kinetic barrier of "surface gelation" that hinders dissolution, thus resulting in limited improvement or excessive cost.

[0004] Therefore, developing a novel rapid dissolution technology that can effectively overcome the dissolution kinetic barrier in principle, is simple in process, cost-controllable, and does not change the main safety and application characteristics of sodium carboxymethyl cellulose has become an urgent and important issue in this field. This invention proposes a novel solution against this backdrop. The core of this solution lies in designing and introducing an inorganic composite modifier with a special microstructure. This material does not alter the cellulose molecular chain itself through complex chemical reactions, but rather acts as a highly efficient "physical promoter," playing a key role in the microscopic process of sodium carboxymethyl cellulose dissolution. Through its unique design, this modifier can effectively interfere with and disrupt the formation of a dense gel layer on the particle surface, while simultaneously creating a permeation channel for water molecules to quickly enter the particle interior. This achieves a significant increase in dissolution rate while ensuring that the original chemical indicators and functional properties of the product remain essentially unchanged. Furthermore, the subsequent modification process is simple and mild, easily integrated with existing production processes, and has significant industrialization prospects and application value. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing fast-dissolving sodium carboxymethyl cellulose, which solves the technical problem of overcoming the defects of traditional sodium carboxymethyl cellulose, such as slow dissolution and easy agglomeration to form a gel barrier.

[0006] The present invention achieves the above objectives through the following technical solutions:

[0007] A method for preparing fast-dissolving sodium carboxymethyl cellulose includes the following steps:

[0008] S1, by weight, 80-120 parts of refined cotton are added to a reactor, and an ethanol solution containing 20-35 parts of sodium hydroxide is added to carry out an alkalization reaction at 30-35℃; 18-25 parts of chloroacetic acid are added, and the temperature is raised to 70-75℃ and maintained; after the reaction is completed, the mixture is cooled to room temperature, the pH is adjusted to 6.5-7.5, and centrifuged to obtain the product; the product is repeatedly washed with an ethanol-water mixture to obtain the washed product; finally, the washed product is dried at 80-95℃, pulverized, and sieved to obtain sodium carboxymethyl cellulose;

[0009] S2, add 0.1-0.5 parts of gradient mesoporous silica core-shell heterostructure modified material based on ZnO nanorod template to 50-100 parts of deionized water, and disperse by ultrasonication to obtain a suspension;

[0010] S3, Place the sodium carboxymethyl cellulose obtained in step S1 into a mixer, spray the suspension onto the surface of the sodium carboxymethyl cellulose, and continue mixing after spraying to obtain a mixture;

[0011] S4. Transfer the mixture to a pan, place the pan in a circulating air drying oven at 35-45℃ to dry, and obtain the product; cool the product to room temperature.

[0012] In this invention, the gradient mesoporous silica core-shell heterostructure modified material based on ZnO nanorod templates is applied to the rapid dissolution modification of sodium carboxymethyl cellulose. Its mechanism essentially utilizes the unique physicochemical properties of this inorganic heterostructure to function as both a "gel barrier disruptor" and a "water transport accelerator" during the dynamic interface process of sodium carboxymethyl cellulose dissolution, rather than reacting chemically with cellulose molecules. When the modified material is uniformly attached to the surface of sodium carboxymethyl cellulose particles at the nanoscale, its hydrophilic silica shell and abundant gradient mesopores enable ultra-fast water molecule adsorption and capillary wetting, far exceeding that of cellulose itself, in the initial instant of water dissolution. This first establishes multiple highly hydrophilic "bridgeheads" on the surface of the sodium carboxymethyl cellulose particles. More importantly, these inorganic particles with nanoscale hardness, embedded in the initially hydrated and swollen flexible gel layer of sodium carboxymethyl cellulose, effectively physically block and tear apart the dense, viscous gel film that would otherwise form continuously, disrupting its integrity and forming microscopic cracks and defects. Meanwhile, the pre-designed gradient mesoporous channel network within the modified material begins to play a crucial role, mimicking a highly efficient water transport system: driven by surface energy and capillary forces, external water is rapidly drawn into the larger pores and quickly conducted along channels that gradually narrow inwards to the particle surface and even the shallow interior. This directional and rapid transport mechanism is equivalent to constructing countless microscopic "water channels" on and near the surface of sodium carboxymethyl cellulose particles, greatly accelerating the rate of water molecule penetration into the particle matrix. This prompts the sodium carboxymethyl cellulose molecular chains to rapidly hydrate, swell, and untangle from the inside, achieving a synergistic dissolution mode combining inside-out and outside-in processes. This mode completely overturns the traditional slow dissolution kinetics of sodium carboxymethyl cellulose, which can only dissolve from the surface inwards and is severely hindered by the gel layer. Therefore, the entire modification process is achieved at the physical level by controlling the interfacial properties and water mass transfer pathways, without altering the molecular chain chemical structure, degree of substitution, and degree of polymerization of sodium carboxymethyl cellulose. Thus, while achieving amazing rapid dissolution performance, it perfectly retains all its inherent bulk application properties such as thickening, adhesion, and safety.

[0013] According to a preferred embodiment of the present invention, in step S1, the time for holding the temperature at 70-75°C is 1.5-2 hours.

[0014] According to a preferred embodiment of the present invention, in step S2, the ultrasonic dispersion time is 30-50 min.

[0015] According to a preferred embodiment of the present invention, in step S3, the mixing time is 20-40 minutes.

[0016] According to a preferred embodiment of the present invention, in step S4, the tray is placed in a circulating air drying oven at 35-45°C for 2-4 hours to dry.

[0017] According to a preferred embodiment of the present invention, the preparation steps of the gradient mesoporous silica core-shell heterostructure modified material based on ZnO nanorod template include:

[0018] A1, by weight, dissolve 10-15 parts of zinc nitrate hexahydrate in 200-300 parts of deionized water. While stirring, add dropwise an aqueous solution containing 8-12 parts of sodium hydroxide to obtain a mixed solution. Transfer the mixed solution to a high-pressure reactor and perform a hydrothermal reaction in a forced-air drying oven at 115-125℃. After the reaction is complete, allow it to cool naturally to room temperature to obtain a reaction mixture. Separate the reaction mixture by centrifugation, collect the product, and wash the product with deionized water and anhydrous ethanol to obtain the washed product. Dry the washed product in a vacuum drying oven at 58-62℃ to obtain ZnO nanorods.

[0019] A2, the ZnO nanorods obtained in step A1 are ultrasonically dispersed in a mixed solution of 80-120 parts anhydrous ethanol, 20-30 parts deionized water, and 1.5-2.5 parts ammonia. At 34-36℃ with stirring, 1.0-2.0 parts of tetraethyl orthosilicate dissolved in anhydrous ethanol are added, along with 0.4-0.8 parts of hexadecyltrimethylammonium bromide dissolved in a mixture of anhydrous ethanol and deionized water. After the addition is complete, the reaction continues at 34-36℃. After the reaction is complete, the product is collected by centrifugation and washed with ethanol to obtain the washed product.

[0020] A3. The washed product is redispersed in deionized water; the mixture is stirred at 38-42℃, and 10-20 parts of a buffer solution of ammonium fluoride and hydrochloric acid with a pH of 4.5-5.0 are added to react. The solid is collected by centrifugation and washed with deionized water to obtain the washed solid.

[0021] A4. Place the washed solid in a tube furnace and perform programmed calcination in an air atmosphere: heat to 345-355℃ and hold; then continue heating to 400-420℃ and hold; after calcination, cool the furnace to room temperature.

[0022] In this invention, the gradient mesoporous silica core-shell heterostructure modified material based on ZnO nanorod templates embodies an innovative approach from microstructure design to macroscopic performance regulation in its preparation and functional mechanism. The synthesis of this material is a multi-step, precise construction process. Its core mechanism lies in the phased realization of "structural template construction," "mesoporous shell coating and guidance," "gradient channel etching," and "final structural thermal stabilization." First, zinc oxide nanorods are synthesized via a hydrothermal method. This process utilizes a high-temperature, high-pressure hydrothermal environment to promote the hydrolysis and directional crystallization growth of zinc salt precursors under alkaline conditions, thereby obtaining a one-dimensional nanostructure with a high aspect ratio and regular morphology. This structure provides an ideal rigid template and morphological basis for subsequent core-shell assembly. Subsequently, under the catalysis of ammonia, tetraethyl orthosilicate undergoes controlled hydrolysis and condensation reactions on the surface of the nanorods, uniformly depositing to form an amorphous silica layer. Simultaneously, cetyltrimethylammonium bromide surfactant molecules present in the system self-assemble into micelles. These micelles act as soft templates, in situ encapsulating the silica matrix, thus introducing an ordered mesoporous structure within the shell. The most crucial step is controlled etching using a fluoride buffer solution. Fluoride ions possess a unique and mild dissolving ability for silica; the reaction mechanism involves fluoride ions combining with silicon-oxygen bonds to form soluble fluorosilicate ions. By precisely controlling the pH and reaction time of the etching solution, a gradient etching process, gradually decreasing in intensity, can be achieved from the outer surface of the shell to near the zinc oxide core region. This creates a three-dimensional, interconnected gradient channel network within the mesoporous framework, with pore sizes gradually decreasing from the surface inwards, rather than uniformly sized channels. The final temperature-calcination process has a dual mechanism: first, it completely decomposes and removes the organic surfactant template embedded in the shell, purifying and solidifying the mesopores; second, it promotes the further condensation and densification of the silica amorphous network through appropriate thermal stress, while ensuring the formation of a stable heterogeneous interface between the zinc oxide core and the silica shell, thereby ultimately obtaining an inorganic composite nanomaterial with a stable structure and unique gradient mesoporous channels.

[0023] According to a preferred embodiment of the present invention, in step A1, the hydrothermal reaction time in a forced-air drying oven at 115-125°C is 12-14 hours.

[0024] According to a preferred embodiment of the present invention, in step A2, the reaction is continued at 34-36°C for 24-30 hours; the mass concentration of the ammonia water is 26-30%.

[0025] According to a preferred embodiment of the present invention, in step A3, the reaction time is 2-3 hours.

[0026] According to a preferred embodiment of the present invention, in step A4, the temperature is further increased to 400-420°C and held for 2-3 hours.

[0027] The beneficial effects of this invention are as follows:

[0028] The method for preparing fast-dissolving sodium carboxymethyl cellulose provided by this invention introduces a carefully designed inorganic heterogeneous composite modified material and adopts a simple subsequent physical mixing process, which produces significant and multifaceted beneficial technical effects and fundamentally overcomes the core drawback of slow dissolution of traditional products.

[0029] Firstly, regarding the final performance of the product, the sodium carboxymethyl cellulose prepared by this method achieves a breakthrough improvement in dissolution speed. The product treated with this invention, upon contact with water, can be wetted and dispersed almost instantaneously, and under conventional stirring conditions, can completely dissolve within minutes to form a homogeneous and transparent solution, completely eliminating visible "fish eyes" or clumps. This contrasts sharply with traditional products that require several hours to completely dissolve, and is even significantly superior to products treated with existing improved technologies such as physical expansion. More importantly, this leap in rapid solubility is achieved while completely preserving the main chemical structure of sodium carboxymethyl cellulose. Key indicators of the product, such as intrinsic viscosity, degree of substitution, solution transmittance, and thermal storage stability, are essentially consistent with those of the unmodified high-quality raw material. This means that its core functional attributes, upon which it relies in various applications, are fully preserved, without sacrificing its basic performance as a thickener, binder, or stabilizer in pursuit of dissolution speed, thus meeting the stringent requirements of high-end applications for a comprehensive balance of material performance.

[0030] Secondly, this method demonstrates significant advantages and industrialization potential in terms of production technology and cost control. The entire modification process is characterized by mild conditions and simple operation. The core rapid dissolution steps involve only liquid-phase dispersion of the modified material, surface spraying, and low-temperature drying. These are all conventional physical processing unit operations, requiring no complex chemical reaction vessels or demanding temperature and pressure control equipment. This results in low energy consumption, a short production process, minimal safety risks, and easy integration with existing sodium carboxymethyl cellulose production lines, making it suitable for large-scale, stable production. Furthermore, the highly efficient modified material requires only a low dosage, making the modification cost negligible and avoiding the problems of decreased product purity or introduction of impurities caused by adding large amounts of additives. It also ensures that the dominant component of cellulose ether in the final product remains unaffected. This method provides a highly efficient path to product performance upgrades through a simplified process and minimal amounts of highly efficient additives, offering outstanding economic benefits.

[0031] Finally, at the level of technical principles and innovation, this method provides a novel approach to solving the bottleneck of polysaccharide dissolution kinetics. Its effectiveness stems from the unique inorganic heterostructure-modified material, which, by mimicking efficient transport mechanisms in nature, plays a dual role at the microscale as both a "fast water molecule channel" and a "gel layer disruptor." When attached to the surface of sodium carboxymethyl cellulose particles, it not only physically hinders the formation of a dense, continuous gel film, but its unique gradient mesoporous channels also actively adsorb and rapidly transfer water molecules to the particle interior, triggering synergistic swelling from the inside out. This overturns the slow, layer-by-layer blockage pattern of traditional dissolution processes. This strategy of regulating the dissolution interface process of polymer materials by externally introducing nanomaterials with specific physical structures is not only novel and unique, but also opens up new research directions for the performance improvement of other types of water-soluble polymers or poorly soluble functional materials, possessing significant inspirational value and broad application prospects. Detailed Implementation

[0032] The following detailed embodiments are only used to further illustrate this application and should not be construed as limiting the scope of protection of this application. Those skilled in the art can make some non-essential improvements and adjustments to this application based on the above application content.

[0033] Example 1

[0034] Preparation of Gradient Mesoporous Silica Core-Shell Heterostructure Modified Materials Based on ZnO Nanorod Templates

[0035] Step A1: Accurately weigh 12.0 g of zinc nitrate hexahydrate and place it in a 500 mL beaker. Add 250 mL of deionized water and stir at 500 rpm on a magnetic stirrer until completely dissolved. While continuously stirring, add 100 mL of sodium hydroxide aqueous solution (prepared by dissolving 10.0 g of NaOH solid in deionized water, concentration 2.0 mol / L) dropwise using a constant pressure dropping funnel, controlling the dropping rate to approximately 2 mL / min. After the addition is complete, continue stirring for 30 min to obtain a homogeneous milky white mixed solution. Transfer this mixed solution entirely to a 500 mL stainless steel high-pressure reactor lined with polytetrafluoroethylene, ensuring a filling degree of approximately 70%. Seal the reactor and place it in a forced-air drying oven. Start heating from room temperature, raise the temperature to 120 °C, and maintain this temperature for 13 h for hydrothermal reaction. After the reaction is complete, turn off the power to the drying oven and allow the reactor to cool naturally to room temperature (approximately 25 °C). Open the reaction vessel and transfer the entire reaction mixture to a 250 mL centrifuge tube. Centrifuge at 8000 rpm for 10 min and discard the supernatant. Wash the collected white precipitate with 200 mL of deionized water and centrifuge again, repeating this process three times. Then wash and centrifuge three times with 200 mL of anhydrous ethanol. Transfer the washed product to a petri dish and dry it in a vacuum drying oven at 60 °C for 6 h to obtain dry, loose zinc oxide nanorod powder.

[0036] Step A2: Accurately weigh 1.00 g of the ZnO nanorod powder prepared above and place it in a 250 mL three-necked flask. Add 100 mL of anhydrous ethanol, 25 mL of deionized water, and 2.0 mL of 28% concentrated ammonia solution to the flask. Place the flask in a 35°C constant temperature water bath, install a mechanical stirrer (paddle stirrer), and stir at a rate of 400 rpm. Simultaneously, turn on the ultrasonic probe connected to the flask (power 200 W, working for 2 seconds, then intermittent for 3 seconds) to assist dispersion for 30 min, obtaining a uniformly dispersed suspension. Prepare two 50 mL constant pressure dropping funnels. Add a mixture of 1.5 mL of tetraethyl orthosilicate (TEOS) and 20 mL of anhydrous ethanol to funnel A, and add a mixture of 0.60 g of hexadecyltrimethylammonium bromide (CTAB) dissolved in 20 mL of anhydrous ethanol and 10 mL of deionized water to funnel B. Simultaneously controlling the stopcocks of two funnels, the two solutions were added dropwise to a vigorously stirred ZnO suspension at a rate of approximately 0.5 mL / min, with a total adding time of about 1 h. After the addition was complete, the dropping funnels were removed, and the reaction was continued at a water bath temperature of 35 °C and a stirring rate of 400 rpm for 28 h. After the reaction was complete, the entire mixture was transferred to a centrifuge tube, and the product was collected by centrifugation at 8000 rpm for 10 min. The product was washed three times with 100 mL of anhydrous ethanol by centrifugation to obtain a preliminarily coated ZnO@SiO2 core-shell precursor.

[0037] Step A3: Transfer all the washed core-shell precursor to a 500 mL beaker, add 150 mL of deionized water, and redisperse evenly under a 40°C water bath and magnetic stirring. Prepare a buffer solution with a pH of 4.8 and an ammonium fluoride concentration of 0.10 mol / L using hydrochloric acid and ammonium fluoride. Measure 15.0 mL of this buffer solution and add it to the beaker all at once while stirring. Maintain the 40°C water bath temperature and stirring, allowing the etching reaction to continue for 2.5 h. After the reaction is complete, centrifuge the mixture (8000 rpm, 10 min) and collect the solid. Wash the solid with deionized water by centrifugation until no chloride ion precipitate is detected in the supernatant using silver nitrate solution (usually 5-6 times), obtaining the etched solid.

[0038] Step A4: Place the washed solid in an alumina ceramic boat and then place it in the isothermal zone of a tube furnace. Aeration is initiated at a flow rate of 100 mL / min, followed by a programmed temperature increase: first, the temperature is increased from room temperature to 350 °C at a rate of 2 °C / min and held at 350 °C for 2 hours; then, the temperature is increased to 410 °C at a rate of 2 °C / min and held at 410 °C for 2.5 hours. After the calcination program is complete, the heating power is turned off, and the tube furnace is allowed to cool naturally to below 80 °C while maintaining continuous air circulation. The sample is then removed, yielding a gradient mesoporous silica core-shell heterostructure modified material based on a ZnO nanorod template. This material is then ground and ready for use.

[0039] Preparation of Instantly Dissolving Sodium Carboxymethyl Cellulose

[0040] Step S1: In a 2L glass reactor equipped with a jacket and anchor stirrer, add 100g of refined cotton. Dissolve 30g of sodium hydroxide solid in 470mL of deionized water, then mix with 500mL of anhydrous ethanol to prepare an ethanol-alkali solution with a mass fraction of approximately 88%. Add this ethanol-alkali solution to the reactor all at once, start stirring (120rpm) and turn on the jacket circulating water, control the reaction system temperature at 32±2℃, and carry out the alkalization reaction for 80min. After alkalization, add 22g of chloroacetic acid solid to the reactor all at once. By adjusting the jacket circulating hot water, raise the reaction system temperature uniformly to 73℃ within 60min, and maintain this temperature for etherification reaction for 108min. After the reaction, cool the material rapidly to below 30℃ using cooling water. Use a 10% hydrochloric acid solution to slowly neutralize the reaction mixture to pH 7.0 with stirring. Transfer the neutralized slurry to a centrifuge and centrifuge at 4500rpm for 15min to separate the crude product filter cake. The filter cake was broken up again and washed with 500 mL of ethanol-water mixture (7:3 volume ratio) for 10 min, followed by centrifugation. This washing-centrifugation process was repeated four times. The final washed filter cake was spread on a stainless steel tray and dried in a 90°C forced-air drying oven for 8 h until constant weight was achieved. The dried lumps were first crushed using a coarse pulverizer, then pulverized using a universal pulverizer, and finally passed through an 80-mesh (180 μm aperture) standard sieve to obtain sodium carboxymethyl cellulose base powder.

[0041] Step S2: Accurately weigh 0.20 g of the self-made gradient mesoporous silica core-shell heterostructure modified material based on ZnO nanorod template and place it in a 100 mL beaker. Add 80 mL of deionized water, then place the beaker in an ultrasonic cleaner (300 W power, 40 kHz frequency) and ultrasonically disperse for 40 min until a uniform, stable, milky white suspension with no obvious sedimentation is obtained.

[0042] Step S3: Weigh 100g of the sodium carboxymethyl cellulose base powder obtained in Step S1 and place it in a 10L three-dimensional motion mixer. With the mixer running at 20rpm, use a 0.5mm nozzle atomizing spray gun to evenly spray the entire suspension prepared in Step S2 into a mist onto the continuously churning powder surface. During the spraying process, control the inlet air temperature to approximately 50℃ to ensure rapid evaporation of moisture. After spraying, continue mixing for 30 minutes to further homogenize the material.

[0043] Step S4: Spread the mixed material evenly on multiple stainless steel trays, controlling the material layer thickness to 1.5cm. Place the trays in a 40℃ circulating air drying oven and dry for 3 hours. After drying, move the material to room temperature (25℃) to cool down, then seal and package to obtain the instant carboxymethyl cellulose sodium product.

[0044] Example 2

[0045] The specific implementation method is the same as in Example 1, except that the modified material is a gradient mesoporous silica core-shell heterostructure based on ZnO nanorod templates.

[0046] Step A1: Accurately weigh 10.0 g of zinc nitrate hexahydrate and dissolve it in 200 mL of deionized water. While stirring, add 80 mL of an aqueous solution containing 8.0 g of sodium hydroxide dropwise at a rate of 2 mL / min to obtain a mixed solution. Transfer this solution to a 500 mL high-pressure reactor and carry out a hydrothermal reaction at 118 °C for 12 h. After natural cooling, centrifuge the reaction mixture at 8000 rpm for 10 min to collect the precipitate, and wash it three times each with deionized water and anhydrous ethanol. Dry the product in a vacuum drying oven at 60 °C for 6 h to obtain zinc oxide nanorod powder.

[0047] Step A2: Weigh 1.00 g of the above ZnO nanorods and disperse them in a mixed solution consisting of 80 mL of anhydrous ethanol, 20 mL of deionized water, and 1.8 mL of 28% ammonia solution. Under a 34°C water bath and mechanical stirring at 400 rpm, simultaneously add 1.0 mL of tetraethyl orthosilicate dissolved in 15 mL of anhydrous ethanol, and a mixture of 0.40 g of hexadecyltrimethylammonium bromide dissolved in 15 mL of anhydrous ethanol and 8 mL of deionized water, controlling the total adding time to approximately 50 min. After the addition is complete, continue the reaction at 34°C for 24 h. After the reaction is complete, collect the product by centrifugation and wash it three times with anhydrous ethanol.

[0048] Step A3: Redisperse the above product in 120 mL of deionized water and stir at 38 °C. Add 10.0 mL of a buffer solution with pH 4.5 and an ammonium fluoride concentration of 0.10 mol / L, and react for 2.0 h. After the reaction, collect the solid by centrifugation and wash with deionized water until neutral.

[0049] Step A4: The solid was placed in a tube furnace and heated to 350℃ at a rate of 2℃ / min under air atmosphere, and held for 2 hours. Then, the temperature was increased to 400℃ at the same rate and held for 2.0 hours. After furnace cooling, a gradient mesoporous silica core-shell heterostructure modified material based on a ZnO nanorod template was obtained.

[0050] Preparation of Instantly Dissolving Sodium Carboxymethyl Cellulose

[0051] Step S1: Add 80g of refined cotton to the reactor, along with an alkaline solution prepared from 20g of sodium hydroxide and 380mL of 88% ethanol. Incubate the reaction at 30℃ for 60min. Add 18g of chloroacetic acid, heat to 70℃ and maintain the temperature for 90min. After cooling, neutralize to pH 7.0 and centrifuge. Wash the product four times with a 7:3 volume ratio of ethanol-water solution, dry to constant weight at 85℃, and pulverize through an 80-mesh sieve to obtain the basic powder.

[0052] Step S2: Weigh 0.08g of the gradient mesoporous silica core-shell heterostructure modified material based on ZnO nanorod template, add 50mL of deionized water, and ultrasonically disperse for 30min to obtain a suspension.

[0053] Step S3: Weigh 80g of base powder and place it in a mixer. Spray the entire suspension while the mixer is running. Continue mixing for 20 minutes after spraying.

[0054] Step S4: Spread the mixture evenly in a tray, dry it in a 35°C circulating air drying oven for 2 hours, and cool it to room temperature to obtain the finished product.

[0055] Example 3

[0056] The specific implementation method is the same as in Example 1, except that the modified material is a gradient mesoporous silica core-shell heterostructure based on ZnO nanorod templates.

[0057] Step A1: Accurately weigh 15.0 g of zinc nitrate hexahydrate and dissolve it in 300 mL of deionized water. While stirring, add 120 mL of an aqueous solution containing 12.0 g of sodium hydroxide dropwise at a rate of 2 mL / min to obtain a mixed solution. Transfer this solution to a 500 mL high-pressure reactor and carry out a hydrothermal reaction at 125 °C for 14 h. After natural cooling, centrifuge the reaction mixture at 8000 rpm for 10 min to collect the precipitate, and wash it three times each with deionized water and anhydrous ethanol. Dry the product in a vacuum drying oven at 60 °C for 6 h to obtain zinc oxide nanorod powder.

[0058] Step A2: Weigh 1.00 g of the above ZnO nanorods and disperse them in a mixed solution consisting of 120 mL of anhydrous ethanol, 30 mL of deionized water, and 2.2 mL of 28% ammonia solution. Under a 36°C water bath and mechanical stirring at 400 rpm, simultaneously add 2.0 mL of tetraethyl orthosilicate dissolved in 25 mL of anhydrous ethanol, and a mixture of 0.80 g of hexadecyltrimethylammonium bromide dissolved in 25 mL of anhydrous ethanol and 12 mL of deionized water, controlling the total adding time to approximately 70 min. After the addition is complete, continue the reaction at 36°C for 30 h. After the reaction is complete, collect the product by centrifugation and wash it three times with anhydrous ethanol.

[0059] Step A3: Redisperse the above product in 180 mL of deionized water and stir at 42 °C. Add 20.0 mL of a buffer solution with pH 5.0 and an ammonium fluoride concentration of 0.10 mol / L, and react for 3.0 h. After the reaction, collect the solid by centrifugation and wash with deionized water until neutral.

[0060] Step A4: The solid was placed in a tube furnace and heated to 350℃ at a rate of 2℃ / min under air atmosphere, and held for 2 hours. Then, the temperature was increased to 420℃ at the same rate and held for 3.0 hours. After furnace cooling, a gradient mesoporous silica core-shell heterostructure modified material based on a ZnO nanorod template was obtained.

[0061] Preparation of Instantly Dissolving Sodium Carboxymethyl Cellulose

[0062] Step S1: Add 120g of refined cotton to the reactor, along with an alkaline solution prepared from 35g of sodium hydroxide and 565mL of 88% ethanol. Incubate the reaction at 35℃ for 90min. Add 25g of chloroacetic acid, raise the temperature to 75℃ and maintain the temperature for 120min. After cooling, neutralize to pH 7.0 and centrifuge. Wash the product four times with a 7:3 volume ratio of ethanol-water solution, dry at 95℃ to constant weight, and pulverize through an 80-mesh sieve to obtain the basic powder.

[0063] Step S2: Weigh 0.60g of the gradient mesoporous silica core-shell heterostructure modified material based on ZnO nanorod template, add 100mL of deionized water, and ultrasonically disperse for 50min to obtain a suspension.

[0064] Step S3: Weigh 120g of base powder and place it in a mixer. Spray the entire suspension while the mixer is running. Continue mixing for 40 minutes after spraying.

[0065] Step S4: Spread the mixture evenly in a tray and dry it in a 45°C circulating air drying oven for 4 hours. Cool it to room temperature to obtain the finished product.

[0066] Comparative Example 1

[0067] The specific implementation method is the same as in Example 1, except that this comparative example does not add the gradient mesoporous silica core-shell heterostructure modification material based on ZnO nanorod templates. The preparation process of sodium carboxymethyl cellulose base powder is exactly the same as in Example 1, yielding 100g of base powder. In the modification step, only 80mL of deionized water (without the gradient mesoporous silica core-shell heterostructure modification material based on ZnO nanorod templates) is placed in a beaker and treated in an ultrasonic cleaner under the same conditions (300W, 40kHz) for 40min. Subsequently, in a three-dimensional motion mixer, 100g of base powder and this 80mL of pure water are treated with the same spraying, mixing, drying, and cooling process as in Example 1 to obtain the comparative sample.

[0068] Comparative Example 2

[0069] The specific implementation method is the same as in Example 1, except that ordinary fumed silica nanoparticles (particle size approximately 20 nm, specific surface area approximately 200 m² / g) are used instead of the gradient mesoporous silica core-shell heterostructure modified material based on ZnO nanorod templates. 0.20 g of the silica was weighed and added to 80 mL of deionized water, and ultrasonically dispersed in an ultrasonic cleaner under the same conditions for 40 min to obtain a suspension. The preparation of sodium carboxymethyl cellulose base powder was the same as in Example 1, yielding 100 g of base powder. This base powder and the aforementioned silica suspension were treated using the same spraying, mixing, drying, and cooling process as in Example 1 to obtain the comparative sample.

[0070] Comparative Example 3

[0071] The specific implementation method is the same as in Example 1, except that the etching process with ammonium fluoride buffer solution is omitted when preparing the gradient mesoporous silica core-shell heterostructure modified material based on ZnO nanorod templates in this comparative example. The preliminary steps (A1 and A2) for preparing the gradient mesoporous silica core-shell heterostructure modified material based on ZnO nanorod templates are exactly the same as in Example 1, until the ZnO@SiO2 core-shell precursor is obtained. Afterwards, the etching reaction in step A3 is not performed; instead, the washed core-shell precursor is directly subjected to the programmed temperature calcination in step A4. The calcination conditions (increasing to 350℃ at 2℃ / min and holding for 2h, then increasing to 410℃ and holding for 2.5h) are exactly the same as in Example 1, resulting in an unetched core-shell material with uniform mesopores. Using 0.20g of this unetched material, sodium carboxymethyl cellulose comparative samples are prepared according to the same steps S2-S4 as in Example 1.

[0072] Performance testing

[0073] The instant carboxymethyl cellulose sodium prepared in Examples 1-3 and Comparative Examples 1-3 above was subjected to performance testing according to the following method, which included the following steps: performance testing was performed on the products obtained in the examples and comparative examples of the present invention. All tests were conducted in a constant temperature and humidity room with a temperature of 25±1℃ and a relative humidity of 50±5%.

[0074] Complete Dissolution Time Test: Accurately weigh 1.00 g of the sample powder using an analytical balance. Pour 99 mL of deionized water into a clean 250 mL low-profile beaker and place it on a magnetic stirrer with a 40 mm long PTFE stir bar. Start the magnetic stirrer and pre-adjust and fix the speed at 500 rpm. Spread the weighed sample evenly and evenly over the center of the rapidly rotating liquid surface in one go, and immediately start timing with a stopwatch. Subsequently, briefly turn off the stirrer for 2 seconds every 15 seconds to visually observe the bottom of the beaker and the solution for any undissolved particles or "fish eyes". Stop timing when the solution is completely homogeneous and transparent, and there are no visible undissolved substances at the bottom or on the surface. The time recorded in this process is the complete dissolution time. Each sample is tested in parallel three times, and the arithmetic mean is taken as the final result.

[0075] Initial wetting time test: Accurately weigh 0.10 g of the sample powder using an analytical balance. Pour 100 mL of deionized water into a 150 mL crystallizing dish and allow it to stand until the liquid surface is completely stable. Prepare a 100-mesh standard sieve and place the weighed sample in the sieve. Hold the sieve with its lower edge 10 cm above the still liquid surface and gently and evenly vibrate it, allowing the powder to fall naturally to the liquid surface within approximately 5 seconds. Start timing with a stopwatch from the moment the first powder particle touches the liquid surface, continuously observe, and record the time taken until all powder is completely submerged in water and no more particles are floating on the liquid surface. This time is the initial wetting time. Each sample is tested in parallel five times, and the arithmetic mean is taken as the final result.

[0076] 1% Solution Viscosity Test: Prepare 100g of a completely dissolved and homogeneous 1% concentration sample solution according to the "Complete Dissolution Time Test" method described above. Let the solution stand for 30 minutes to eliminate air bubbles introduced by stirring. Select a suitable rotor and inject approximately 20mL of the solution into the measuring cup of the rotational viscometer. Under the control of a 25℃ constant temperature water bath, set the rotor speed to 60rpm and start the measurement. After the instrument reading stabilizes, read and record the apparent viscosity value. Test each sample three times and take the arithmetic mean.

[0077] Solution transparency test: Use the 1% concentration sample solution prepared above and allowed to stand. First, rinse the quartz cuvette with deionized water for 1 cm optical path, then rinse three times with the test solution. Pour the solution into the cuvette to about 3 / 4 of its height, ensuring the outer wall is clean and free of liquid and the interior is free of air bubbles. Using deionized water as a 100% transmittance reference, measure the transmittance of the sample at a wavelength of 660 nm using a UV-Vis spectrophotometer. Test each sample three times and take the arithmetic mean.

[0078] Simulated battery slurry dispersion time test: 2.00 g of the sample powder was accurately weighed using an analytical balance. 98 g of deionized water was added to a 500 mL plastic beaker, which was then placed under a high-speed disperser. A 50 mm serrated dispersion disc was installed, and the disc was adjusted to be immersed approximately 1 / 3 of the way below the liquid surface. The disperser was started, and the speed was set to 500 rpm. The sample powder was slowly added to the center of the vortex. After the addition was complete, the mixture was stirred at this speed until the solution was completely homogeneous and transparent, yielding a 2% sodium carboxymethyl cellulose stock solution. Subsequently, while maintaining a stirring speed of 500 rpm, 50 g of artificial graphite anode material was added to the stock solution in three portions, with a 2-minute interval between each addition to ensure the powder was basically wetted. After all the graphite was added, the stirring speed was increased to 2000 rpm, and a stopwatch was started from this point. Dispersion was continued at 2000 rpm, during which time the adhering material on the beaker wall was scraped off with a spatula every 1 minute. Observe the state of the slurry. Stop timing when it becomes uniform, smooth, and fine like lacquer, with no particle accumulation on the disc and no visible hard particle clumps when checked with a scraper. The time recorded in this process is the simulated slurry dispersion time.

[0079] Test results:

[0080] Table 1: Test results of each embodiment and comparative example

[0081] Test Project Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Complete dissolution time (min) 4.8 5.5 5.0 >60 (Incomplete) 28.5 18.2 Initial wetting time (s) <3 4 3 >30 12 8 Viscosity of 1% solution (mPa·s) 1480 1510 1450 1520 1485 1495 Solution transparency (%T, 660nm) 95.2 94.8 94.5 93.8 94.2 94.9 Simulated slurry dispersion time (min) 15 17 16 45 26 22

[0082] As can be seen from Table 1, Examples 1-3, compared with Comparative Examples 1-3, significantly and consistently demonstrate that the present invention has successfully overcome the core defects of traditional sodium carboxymethyl cellulose, such as slow dissolution rate and easy agglomeration to form a gel barrier.

[0083] Specifically, the products in the examples achieved a breakthrough improvement in complete dissolution time, dissolving completely in just about 5 minutes. In contrast, the product in Comparative Example 1, without any modifier, failed to dissolve completely after 60 minutes, forming stubborn gel clumps. This directly confirms the existence of dissolution kinetic barriers in traditional products. The initial wetting time of the products in the examples was extremely short, all within 4 seconds, far shorter than the wetting time of Comparative Example 1, which exceeded 30 seconds. This indicates that the modified material greatly enhances the hydrophilicity of the powder particle surface, disrupts the hydrophobic or electrostatic interactions that lead to clumping, and allows moisture to instantly contact and encapsulate each particle, fundamentally preventing the formation of surface gel clumps due to uneven wetting.

[0084] Comparative Example 2 uses ordinary SiO2 nanoparticles, and although its solubility and wetting properties are better than those of the unmodified Comparative Example 1, they are still far inferior to those of the examples. This clearly reveals the essential functional difference between ordinary physical mixing and the core-shell heterostructure with a specific gradient mesoporous structure used in this invention. The unique structural design of the latter is the key to producing excellent rapid dissolution.

[0085] Comparative Example 3 uses a core-shell material that has not been fluorinated and its performance is between that of Comparative Example 2 and the Example. This particularly demonstrates the indispensability of the "gradient mesoporous" structure. Although the unetched material has a core-shell morphology, it lacks a channel network with gradually changing pore sizes from the surface to the inside. Its water transport efficiency is limited, resulting in a dissolution rate that is only about 1 / 3 of that of the Example. This strongly confirms the decisive role of gradient mesoporous structures in breaking down the gel barrier and constructing rapid water molecule transport channels.

[0086] Furthermore, all embodiments achieved rapid dissolution while maintaining the same excellent viscosity and transparency as the comparative products. This definitively demonstrates that the modification of this invention is a purely physical interfacial process that does not impair the chemical structure and application performance of sodium carboxymethyl cellulose molecules. Thus, while solving the dissolution rate problem, it fully preserves its value as a functional material. Therefore, comprehensive analysis of the test data shows that this invention, by introducing a unique gradient mesoporous inorganic heterostructure material, effectively solves a series of chain problems such as poor initial wetting, surface gelation inhibition, and slow water penetration, achieving highly efficient rapid dissolution while maintaining the bulk properties.

[0087] The embodiments described above are merely examples of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

Claims

1. A method for preparing fast-dissolving sodium carboxymethyl cellulose, characterized in that, Includes the following steps: S1, by weight, 80-120 parts of refined cotton are added to a reactor, and an ethanol solution containing 20-35 parts of sodium hydroxide is added to carry out an alkalization reaction at 30-35℃; 18-25 parts of chloroacetic acid are added, and the temperature is raised to 70-75℃ and kept at that temperature; after the reaction is completed, the mixture is cooled to room temperature, the pH is adjusted to 6.5-7.5, and the mixture is centrifuged to obtain the product; The product was repeatedly washed with an ethanol-water mixture to obtain the washed product. Finally, the washed product was dried at 80-95℃, pulverized, and sieved to obtain sodium carboxymethyl cellulose. S2, add 0.1-0.5 parts of gradient mesoporous silica core-shell heterostructure modified material based on ZnO nanorod template to 50-100 parts of deionized water, and disperse by ultrasonication to obtain a suspension; S3, Place the sodium carboxymethyl cellulose obtained in step S1 into a mixer, spray the suspension onto the surface of the sodium carboxymethyl cellulose, and continue mixing after spraying to obtain a mixture; S4. Transfer the mixture to a pan, place the pan in a circulating air drying oven at 35-45℃ to dry, and obtain the product; cool the product to room temperature.

2. The method for preparing fast-dissolving sodium carboxymethyl cellulose according to claim 1, characterized in that, In step S1, the temperature is raised to 70-75℃ and held for 1.5-2 hours.

3. The method for preparing fast-dissolving sodium carboxymethyl cellulose according to claim 1, characterized in that, In step S2, the ultrasonic dispersion time is 30-50 minutes.

4. The method for preparing the fast-dissolving sodium carboxymethyl cellulose according to claim 1, characterized in that, In step S3, the mixing time continues for 20-40 minutes.

5. The method for preparing fast-dissolving sodium carboxymethyl cellulose according to claim 1, characterized in that, In step S4, the tray is placed in a circulating air drying oven at 35-45℃ for 2-4 hours to dry.

6. The method for preparing the fast-dissolving sodium carboxymethyl cellulose according to any one of claims 1-5, characterized in that, The preparation steps of the gradient mesoporous silica core-shell heterostructure modified material based on ZnO nanorod template include: A1, by weight, dissolve 10-15 parts of zinc nitrate hexahydrate in 200-300 parts of deionized water. While stirring, add dropwise an aqueous solution containing 8-12 parts of sodium hydroxide to obtain a mixed solution. Transfer the mixed solution to a high-pressure reactor and perform a hydrothermal reaction in a forced-air drying oven at 115-125℃. After the reaction is complete, allow it to cool naturally to room temperature to obtain a reaction mixture. Separate the reaction mixture by centrifugation, collect the product, and wash the product with deionized water and anhydrous ethanol to obtain the washed product. Dry the washed product in a vacuum drying oven at 58-62℃ to obtain ZnO nanorods. A2, the ZnO nanorods obtained in step A1 are ultrasonically dispersed in a mixed solution of 80-120 parts anhydrous ethanol, 20-30 parts deionized water, and 1.5-2.5 parts ammonia. At 34-36℃ with stirring, 1.0-2.0 parts of tetraethyl orthosilicate dissolved in anhydrous ethanol are added, along with 0.4-0.8 parts of hexadecyltrimethylammonium bromide dissolved in a mixture of anhydrous ethanol and deionized water. After the addition is complete, the reaction continues at 34-36℃. After the reaction is complete, the product is collected by centrifugation and washed with ethanol to obtain the washed product. A3. The washed product is redispersed in deionized water; the mixture is stirred at 38-42℃, and 10-20 parts of a buffer solution of ammonium fluoride and hydrochloric acid with a pH of 4.5-5.0 are added to react. The solid is collected by centrifugation and washed with deionized water to obtain the washed solid. A4. Place the washed solid in a tube furnace and perform programmed calcination in an air atmosphere: heat to 345-355℃ and hold; then continue heating to 400-420℃ and hold; after calcination, cool the furnace to room temperature.

7. The method for preparing the fast-dissolving sodium carboxymethyl cellulose according to claim 6, characterized in that, In step A1, the hydrothermal reaction time in a forced-air drying oven at 115-125℃ is 12-14 hours.

8. The method for preparing the fast-dissolving sodium carboxymethyl cellulose according to claim 6, characterized in that, In step A2, the reaction continues at 34-36℃ for 24-30 hours; the mass concentration of the ammonia water is 26-30%.

9. The method for preparing the fast-dissolving sodium carboxymethyl cellulose according to claim 6, characterized in that, In step A3, the reaction time is 2-3 hours.

10. The method for preparing the fast-dissolving sodium carboxymethyl cellulose according to claim 6, characterized in that, In step A4, the temperature is further increased to 400-420℃ and held for 2-3 hours.