Preparation method of special precipitated silicon dioxide for high-silicon tire formula

Abstract

The application discloses a preparation method of precipitated silicon dioxide special for high-silicon tire formula, and the preparation method comprises the following steps: S1, raw material preparation, preparing water glass solution and dilute sulfuric acid for standby; S2, parallel flow reaction, adding deionized water into a reaction kettle as bottom water, and adding the water glass solution and the dilute sulfuric acid solution into the bottom water in parallel flow; S3, silicon source supplement, stopping the parallel flow dropping, and only continuing to drop the water glass solution; S4, acidification, stopping dropping the water glass solution, and replacing the water glass solution with the dilute sulfuric acid solution; S5, aging, aging the system after acidification at constant temperature; and S6, post-treatment. Through the process optimization of adding deionized water, parallel flow growth, separately supplementing a silicon source and precise acidification, the product prepared by the application has a dispersion grade greater than or equal to 9.8, the high structure characteristic can significantly improve the tensile strength and tear strength of rubber, the low surface hydroxyl group density can reduce the hysteresis loss of rubber, reduce the rolling resistance of a tire, and meanwhile improve the wet skid resistance.

Description

Technical Field

[0001] This invention relates to the field of silica preparation technology, and in particular to a method for preparing precipitated silica for high-silica formulations. Background Technology

[0002] Precipitated silica plays a crucial role as a reinforcing filler in rubber, particularly in the formulations of "green tires" and "high-silica tires." By forming a stable three-dimensional network structure within a polymer network, it significantly improves the tensile strength, tear strength, and abrasion resistance of rubber products. With the increasing demands for driving range from new energy vehicles, the market is placing more stringent requirements on tires, demanding lower rolling resistance, higher wet grip, and longer service life. This necessitates that reinforcing silica possess superior dispersibility, a higher degree of structure, and more suitable interfacial properties.

[0003] Traditional precipitation-based silica preparation processes typically employ a precipitation reaction of sodium silicate and acid, controlling the particle size, specific surface area, and structure of silica by manipulating reaction conditions. However, conventional one-step precipitation or simple co-flow processes often fail to achieve precise and synergistic control over particle nucleation, growth, aggregation, and surface properties. During synthesis, particles are prone to uncontrolled agglomeration, forming hard aggregates that are difficult to effectively disperse and uniformly disperse during rubber compounding, creating reinforcement "dead zones." This not only weakens the reinforcement effect but also becomes stress concentration points, accelerating rubber fatigue damage. Furthermore, while a high specific surface area and abundant surface silanol groups are beneficial for interaction with rubber molecules, providing good reinforcement, excessive surface hydroxyl groups can also lead to increased friction in rubber molecular chains during dynamic deformation, resulting in significant hysteresis loss and increased tire rolling resistance. Conversely, excessively reducing surface active sites to reduce hysteresis sacrifices reinforcement performance. Therefore, this paper proposes a method for preparing precipitated silica specifically for high-silica tire formulations to address the aforementioned problems. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing precipitated silica specifically for high-silica formulations, so as to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a method for preparing precipitated silica for high-silica formulations, the preparation method comprising the following steps:

[0006] S1, Raw material preparation: Solid sodium silicate is used to prepare a water glass solution for later use, and dilute sulfuric acid is prepared for later use; S2, co-current reaction: Deionized water is added to the reactor as bottom water, and the temperature is kept constant by heating. Water glass solution and dilute sulfuric acid solution are added dropwise to the bottom water in a co-current manner while stirring. S3, add silicon source, stop parallel dropwise addition, and continue to add water glass solution dropwise to adjust the pH of the reaction system to 8.0-8.5. After the addition is completed, continue stirring for 5-10 min. S4, acidification: stop adding water glass solution and instead add dilute sulfuric acid solution to adjust the pH of the reaction system to 4.5-6.5. After stopping the addition of acid, continue stirring for 5-10 minutes. S5, Aging: Maintain the temperature and stirring speed at the end of acidification, and perform isothermal aging on the acidified system for 10-20 minutes to obtain silica precipitate slurry. S6, Post-processing: The aged silica precipitate slurry is filtered, washed and pulped to make a thick slurry, and then dried, crushed and classified to obtain the highly dispersed precipitated hydrated silica.

[0007] Preferably, the solid sodium silicate has a modulus of 3.0-3.5, the water glass solution has a concentration of 18-20 wt%, and the dilute sulfuric acid has a concentration of 15-20 wt%.

[0008] Preferably, during the co-current reaction, the reactor is heated to 45-50°C and kept at a constant temperature, and the pH value of the reaction system is 6.5-7.5 during the co-current droplet addition process, until the volume of the reaction system reaches two-thirds of the reactor volume.

[0009] Preferably, during the co-current dripping process, the stirring speed is controlled at 100-120 r / min, and the reaction time of the entire co-current dripping process is controlled within 40-60 min.

[0010] Preferably, when adding the silicon source, the stirring speed is adjusted to 120-140 r / min, and the reaction temperature of the reactor is controlled at 50-55℃.

[0011] Preferably, after the water glass solution is added dropwise when replenishing the silicon source, the mixture is stirred at a speed of 120-140 r / min for 5-10 min. After stirring, a sample is taken to observe the state of the reaction system.

[0012] Preferably, during the acidification process, the dropping rate is controlled at 6-10 mL / min, the stirring speed is 120-140 r / min, and the reaction temperature is controlled at 50-55℃.

[0013] Preferably, the filtration time is controlled at 20-30 min, and is adjusted appropriately according to the viscosity of the silica precipitate slurry to separate a silica filter cake with a solid content of 20-25%.

[0014] Preferably, the filter cake is continuously stirred during the washing process until the conductivity of the filter cake is <100μS / cm, and the sodium sulfate content in the filter cake is determined by the conductivity of the washing water. The washing continues until the sodium sulfate content of the final product is less than 2%.

[0015] Preferably, the slurry is fed into an airflow dryer to dry it, and then the dried slurry is pulverized by an airflow pulverizer.

[0016] The technical effects and advantages of this invention are as follows: This invention optimizes the process by adding deionized water, co-current growth, separate addition of silicon source, and precise acidification. Combined with gradient heating, staged pH control, and sufficient aging, the prepared product has a dispersion grade of ≥9.8, which can be fully mixed and blended with rubber. Its high structural properties significantly improve the tensile strength and tear strength of rubber, enhancing tire wear resistance. The low surface hydroxyl density reduces rubber hysteresis loss, lowers tire rolling resistance, and improves wet skid resistance, meeting the high-performance requirements of high-silica tires. This invention solves the pain points of traditional products, such as low activity and poor reinforcing effect. Attached Figure Description

[0017] Figure 1 This is a flowchart illustrating the operational implementation of the preparation method of the present invention. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] This invention provides, for example Figure 1 The method for preparing precipitated silica for high-silica formulations, as shown, includes the following steps: S1, Raw material preparation: Solid sodium silicate is used to prepare a water glass solution for later use, and dilute sulfuric acid is prepared for later use; The solid sodium silicate has a modulus of 3.0-3.5, the water glass solution has a concentration of 18-20 wt%, and the dilute sulfuric acid has a concentration of 15-20 wt%. It should be noted that industrial-grade sodium silicate with a modulus of 3.0-3.5 should be selected. The modulus directly affects the structural integrity and activity of silica and is a key indicator for meeting the reinforcement requirements of high-silica substrates. A modulus that is too low will result in a loose product structure and insufficient reinforcement effect; a modulus that is too high will increase the reaction difficulty and easily lead to agglomeration. Industrial-grade sodium silicate is added to the reaction vessel, followed by slow addition of deionized water. The stirring device is turned on at a speed of 50-60 r / min and stirred uniformly for 30-40 min. The solution is then diluted to a concentration of 18-20 wt% water glass. After dilution, the solution is filtered using a precision filter with a pore size of 5 μm to remove mechanical impurities and insoluble residues. The solution is allowed to stand for 10-15 min until all bubbles have dissipated before use. This prevents residual bubbles from entering the subsequent reaction system, which could lead to uneven crystal nucleus formation and localized agglomeration. Industrial-grade concentrated sulfuric acid with a concentration of 98% is used. Using a safe operating method of "slow addition of acid while stirring", concentrated sulfuric acid is slowly added dropwise to deionized water at a rate of 5-8 mL / min. At the same time, the cooling device is turned on to strictly control the solution temperature at 25-30℃ to prevent local overheating that could lead to sulfuric acid decomposition and the generation of impurities. This also avoids the high-temperature solution from burning the equipment or causing safety hazards. Stir at a uniform speed for 20-30 min to dilute the sulfuric acid to a concentration of 15-20wt% as an acidifying agent. After dilution, allow it to cool to room temperature for later use to prevent the high-temperature solution from entering the subsequent reaction system, which could damage the reaction environment and affect crystal growth and product structure. S2, co-current reaction: Deionized water is added to the reactor as bottom water, and the temperature is kept constant by heating. Water glass solution and dilute sulfuric acid solution are added dropwise to the bottom water in a co-current manner while stirring. During the co-current reaction, the reactor is heated to 45-50℃ and kept at a constant temperature. During the co-current droplet addition, the pH value of the reaction system is 6.5-7.5 until the volume of the reaction system reaches two-thirds of the reactor volume. During the co-current dripping process, the stirring speed is controlled at 100-120 r / min, and the reaction time is controlled within 40-60 min. It should be noted that deionized water, filling 1 / 6 of the reactor's volume, should be added first. The amount of deionized water added is precisely calculated to provide sufficient reaction space for the subsequent co-current addition of raw materials, while avoiding the effects of too much deionized water leading to an excessively low reaction concentration and affecting reaction efficiency, or too little deionized water causing the system volume to reach its upper limit too quickly after the addition of raw materials, thus failing to ensure sufficient reaction. The added deionized water needs to be simply filtered beforehand to remove suspended impurities, ensuring water quality and preventing impurities from affecting crystal nucleation. The water temperature is controlled within the range of 45-50℃ by steam heating and stabilized for 10-15 minutes to ensure uniform temperature in the reaction system and provide a stable temperature environment for the subsequent co-current reaction. After temperature stabilization, water glass solution and dilute sulfuric acid solution are delivered using a dual peristaltic pump and added simultaneously and uniformly to the deionized water in the reactor using a co-current dropping method. The stirring speed is controlled at 100-120 r / min until the reaction solution reaches 2 / 3 of the reactor volume. The dropping rate of the water glass solution is controlled at 10-15. The dropping rate of the dilute sulfuric acid solution is dynamically adjusted in real time based on the online pH monitoring results. The pH of the reaction system is strictly controlled within the range of 6.5-7.5 throughout the process. Too high a pH will lead to excessively rapid crystal growth and agglomeration, affecting product dispersibility; too low a pH will inhibit crystal growth, resulting in a loose product structure and insufficient reinforcing properties. The co-current dropping process is controlled within 40-60 minutes, and the dropping rate needs to be adjusted reasonably according to the reaction time to ensure that the dropping is completed within the specified time and that the reaction proceeds fully. During the dropping process, the system state is observed in real time. If turbidity, unevenness, or precipitation / agglomeration occurs, it indicates insufficient mixing of raw materials, requiring an appropriate increase in stirring speed. If precipitation / agglomeration occurs, it indicates excessive local pH fluctuations or an unreasonable dropping rate, requiring immediate adjustment of the dilute sulfuric acid dropping rate, fine-tuning of the pH, and increasing the stirring speed to break up the agglomerates. If a large number of bubbles appear, it indicates that the reaction rate is too fast, requiring an appropriate reduction in the dropping rate of both raw materials to ensure a stable reaction. The entire process must avoid localized over-acidity or over-alkaliness to prevent product performance defects such as poor dispersibility, loose structure, or uneven particle size distribution. It is essential to ensure that the crystal nuclei are uniform and small, laying a good foundation for subsequent particle growth. This step is the core stage of silica crystal nucleus formation and initial growth. First, deionized water is added to build the basic reaction system. Then, the reaction supersaturation is controlled by parallel drop addition to ensure uniform crystal nucleus formation and stable growth. This lays the foundation for the product's high dispersion and high structural characteristics. This method differs from the traditional bottom liquid preparation method and makes it easier to control the stability of the reaction system. S3, add silicon source, stop parallel dripping, and continue to add water glass solution dropwise to adjust the pH of the reaction system to 8.0-8.5. After the addition is complete, continue stirring for 5-10 minutes. When adding silicon source, adjust the stirring speed to 120-140 r / min and control the reaction temperature of the reactor at 50-55℃. After the water glass solution is added dropwise when adding silicon source, stir at 120-140 r / min for 5-10 min. After stirring, take a sample to observe the state of the reaction system. It should be noted that after the reaction is complete, the parallel droplet addition operation should be stopped, the peristaltic pump for the dilute sulfuric acid solution should be turned off, and only the peristaltic pump for the water glass solution should be turned on. The remaining water glass solution should be added to the reaction system at a uniform rate, with the dropping rate controlled at 8-12 mL / min. At the same time, the stirring speed should be adjusted to 120-140 r / min. The purpose of appropriately increasing the stirring speed is to ensure that the added water glass solution diffuses quickly and evenly throughout the entire reaction system, reacts fully with the sulfuric acid in the system, avoids local silicon source aggregation, which would lead to particle agglomeration, and promotes further particle growth and aggregation to form a complete three-dimensional dendritic structure. The reaction temperature should be controlled within the range of 50-55℃. This temperature range can accelerate the reaction rate of sodium silicate with the remaining sulfuric acid in the system, promote particle growth, and at the same time avoid excessive temperature that would lead to particle agglomeration and structural damage. The pH value of the system is monitored in real time by an online pH monitoring device. By adjusting the drop rate of the water glass solution, the pH value of the reaction system is precisely adjusted within the range of 8.0-8.5. This pH environment can promote further particle growth, forming a more complete three-dimensional dendritic structure, improving the reinforcing performance and structural stability of the product. The entire silicon source replenishment reaction process is controlled within 25-30 minutes to ensure that the silicon source reacts fully and avoids excessive particle growth and agglomeration due to excessive reaction time, or incomplete conversion of silicon source due to insufficient reaction time, resulting in raw material waste. After the drop is added, the stirring device is not turned off, and the stirring is continued at a speed of 120-140 r / min for 5-10 minutes. The purpose is to ensure that the silicon source in the system reacts fully and that the silicon element is evenly distributed in the reaction system, avoiding local excessive silicon source that leads to particle agglomeration. At the same time, extending the stirring time can promote the complete conversion of unreacted sodium silicate into silicon dioxide, improve raw material utilization, reduce raw material waste, and lower production costs. After stirring, take a sample to observe the state of the reaction system to ensure that the system is uniform, without obvious lumps, and that the particles grow uniformly, in order to prepare for the subsequent acidification process. This step is to further optimize the structural characteristics of the product, improve the DBP oil absorption value of the product, enhance the product's reinforcing effect on rubber, and adapt to the core performance requirements of high silica tires for high wear resistance and high wet skid resistance. S4, acidification: stop adding water glass solution and instead add dilute sulfuric acid solution to adjust the pH of the reaction system to 4.5-6.5. After stopping the addition of acid, continue stirring for 5-10 minutes. During the acidification process, the dropping rate is controlled at 6-10 mL / min, and the mixture is stirred at a speed of 120-140 r / min, while the reaction temperature is controlled at 50-55℃. It should be noted that after the reaction is complete, stop adding water glass solution, turn off the water glass solution peristaltic pump, and restart the dilute sulfuric acid solution peristaltic pump. Add dilute sulfuric acid solution dropwise to the reaction system for acidification. During acidification, control the dropping rate to 6-10 mL / min, and maintain the stirring speed at 120-140 rpm throughout to ensure rapid diffusion of the dilute sulfuric acid solution, uniformly neutralizing excess sodium silicate in the system, avoiding localized over-acidity or over-alkaliness, and ensuring uniform pH changes in the system. Control the reaction temperature within the range of 50-55℃ to avoid temperature fluctuations that could affect the reaction rate, pH control, and particle structure stability. Precisely control the pH value throughout the process using an online pH monitoring device, accurately reducing the system pH to 4.5-6.5 within 15-20 minutes. Too low a pH will result in excessive hydroxyl groups on the product surface, affecting compatibility with rubber and increasing tire rolling resistance; too high a pH will fail to completely stop particle growth, leading to unstable product structure and large batch-to-batch performance fluctuations. After acidification, stop adding sulfuric acid and continue stirring for 5-10 minutes. This step ensures that the pH value of the system is uniform and stable, without any localized over-acid areas, in order to prepare for the subsequent aging process and avoid product structure damage caused by localized over-acidity. This step is to terminate particle growth, adjust the pH value of the system, activate the surface reaction in the subsequent aging process, reduce the hydroxyl content on the product surface, reduce tire rolling resistance, and ensure the compatibility of the product with rubber. It is a key process to ensure that the product is compatible with the low rolling resistance requirements of high-silicone tires. S5, Aging: Maintain the temperature and stirring speed at the end of acidification, and perform isothermal aging on the acidified system for 10-20 minutes to obtain silica precipitate slurry. It should be noted that after the acidification reaction is completed, the stirring speed should be kept constant, and the temperature of the reaction system should not be adjusted. The reaction temperature should be maintained at 50-55℃ for isothermal aging. The aging time should be strictly controlled within 10-20 minutes. If the aging time is too long, the particles will agglomerate excessively, resulting in excessively large particle size and affecting the product's dispersibility. If the aging time is too short, the particle structure cannot be optimized, the surface hydroxyl content will be too high, resulting in poor compatibility with rubber and failing to meet the requirements of high-silicone tires. During the aging process, silica particles will further crystallize and agglomerate to optimize, forming a uniform particle size distribution and a stable three-dimensional dendritic structure. At the same time, the hydroxyl groups on the particle surface will undergo partial condensation reaction, reducing the surface hydroxyl density, reducing the product's hydrophilicity, improving compatibility with rubber, reducing agglomeration during tire compounding, and reducing rolling resistance. During the aging process, the system status should be observed regularly. If precipitation and stratification occur, the stirring speed should be increased appropriately to ensure uniform aging. After aging, a uniform and viscous silica precipitate slurry should be obtained. The slurry should be free of obvious lumps and stratification, and have a uniform texture to ensure that the subsequent filter press process can proceed smoothly. This avoids problems such as filter press blockage and uneven filter cake caused by slurry lumps. This step is one of the key processes to optimize particle structure, reduce surface hydroxyl content, improve product stability, ensure product compatibility with rubber, and further improve the high-structure characteristics of the product. It is also one of the key processes to meet the requirements of high-silica tires. S6, post-processing, involves pressing, washing, and pulping the aged silica precipitate slurry to produce a thick slurry, followed by drying, pulverizing, and grading to obtain highly dispersed precipitated hydrated silica. The filter press time is controlled at 20-30 min, and adjusted appropriately according to the viscosity of the silica precipitate slurry to separate a silica filter cake with a solid content of 20-25%. The filter cake is stirred during the washing process until its conductivity is <100μS / cm. The sodium sulfate content in the filter cake is determined by the conductivity of the washing water. The washing continues until the sodium sulfate content in the final product is less than 2%. The slurry is fed into an airflow dryer to dry it, and then the dried slurry is pulverized by an airflow pulverizer. It should be noted that when feeding the aged silica precipitate slurry into a diaphragm filter press for filtration, the filtration pressure must be strictly controlled at 0.3-0.5 MPa. Too low a pressure will result in incomplete filtration, a low solids content in the filter cake, increased energy consumption for subsequent drying, and difficulty in completely removing impurities. Too high a pressure will cause the filter cake to clump and become too hard, making subsequent pulping difficult and potentially damaging the filter cloth of the filter press. The filtration time should be controlled at 20-30 seconds. The concentration of silica filter cake is adjusted according to the viscosity of the slurry to ensure thorough filtration. The solid content of the separated silica filter cake is strictly controlled between 20-25%. Excessive solid content will result in a hard filter cake that is difficult to disperse during pulping and prone to secondary agglomeration; insufficient solid content will increase energy consumption in subsequent drying processes and reduce production efficiency. After filtration, the filter cake is washed countercurrently with deionized water, continuously agitated to ensure uniform washing, until the conductivity of the filter cake is <100μS / cm. The sodium sulfate content in the filter cake is determined by the conductivity of the washing water, and the final product's sodium sulfate content is controlled to be less than 2%, meeting the impurity requirements for high-silica silica. After washing, the filter cake is sent to a pulper, where an appropriate amount of deionized water is added and the mixture is stirred and pulped to adjust the solid content to 15-25%, producing a uniform, lump-free thick slurry. The thick slurry is then sent to an airflow dryer. The airflow dryer uses hot air generated by natural gas combustion as a heat source. During the drying process, the hot air temperature and drying time are strictly controlled to ensure that the moisture content of the dried granular silica product is controlled at 5-7%. The dried powder is then fed into an airflow pulverizer, with the pulverizing pressure adjusted to 0.6-0.8 MPa. By adjusting the pulverizing pressure, the powder is pulverized to a particle size D50 of 8-12 μm. After pulverization, the powder is sieved through a precision sieving device with a filter screen aperture of 20 μm to remove large particle impurities, resulting in a uniform and fine high-silica precipitated hydrated silica product. The finished product is sealed in packaging and stored in a dry, ventilated warehouse to prevent moisture absorption and clumping, ensuring stable product performance. The BET of the high-silica precipitated hydrated silica product is 175-190 m² / g, and the DBP oil absorption value is 2.0-3.0. The product exhibits the following characteristics: loss on heating 5.0-7.0%, silica content ≥95-98%, loss on ignition ≤7.0%, pH 5.0-8.0, soluble dissociated salts ≤2.0%, dispersion grade ≥9.8, tanδ@60℃ ≤0.15, tanδ@0℃ ≥0.35. This method, through process optimization involving the addition of deionized water, co-current growth, separate addition of silicon source, and precise acidification, combined with gradient heating, staged pH control, and thorough aging, produces a product with a dispersion grade ≥9.8, capable of thorough mixing and integration with rubber, and a DBP oil absorption value of 2.0-3.0. It can significantly improve the tensile strength and tear strength of rubber, and enhance the wear resistance of tires; low surface hydroxyl density <4.0 It can reduce rubber hysteresis loss and lower tire rolling resistance by 15-20% compared to traditional products, while improving wet skid resistance and meeting the high-performance requirements of high-silicone tires. It solves the pain points of low activity and poor reinforcement effect of traditional products.

[0020] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing precipitated silica specifically for high-silica formulations, characterized in that, The preparation method includes the following steps: S1, Raw material preparation: Solid sodium silicate is used to prepare a water glass solution for later use, and dilute sulfuric acid is prepared for later use; S2, co-current reaction: Deionized water is added to the reactor as bottom water, and the temperature is kept constant by heating. Water glass solution and dilute sulfuric acid solution are added dropwise to the bottom water in a co-current manner while stirring. S3, add silicon source, stop parallel dripping, and continue to add water glass solution dropwise to adjust the pH of the reaction system to 8.0-8.

5. After the addition is complete, continue stirring for 5-10 minutes. S4, acidify, stop adding water glass solution dropwise, and instead add dilute sulfuric acid solution dropwise to adjust the pH of the reaction system to 4.5-6.

5. After stopping the addition of acid, continue stirring for 5-10 minutes. S5, Aging: Maintain the temperature and stirring speed at the end of acidification, and perform isothermal aging on the acidified system for 10-20 minutes to obtain silica precipitate slurry. S6, post-processing: The aged silica precipitate slurry is filtered, washed and pulped to make a thick slurry, and then dried, crushed and classified to obtain highly dispersed precipitated hydrated silica.

2. The method for preparing precipitated silica for high-silica formulations according to claim 1, characterized in that, The solid sodium silicate has a modulus of 3.0-3.5, the water glass solution has a concentration of 18-20 wt%, and the dilute sulfuric acid has a concentration of 15-20 wt%.

3. The method for preparing precipitated silica for high-silica formulations according to claim 1, characterized in that, During the co-current reaction, the reactor is heated to 45-50°C and kept at a constant temperature. During the co-current droplet addition process, the pH value of the reaction system is 6.5-7.5 until the volume of the reaction system reaches two-thirds of the reactor volume.

4. The method for preparing precipitated silica for high-silica formulations according to claim 3, characterized in that, During the parallel-flow dripping process, the stirring speed is controlled at 100-120 r / min, and the reaction time of the parallel-flow dripping process is controlled within 40-60 min.

5. The method for preparing precipitated silica for high-silica formulations according to claim 1, characterized in that, When adding the silicon source, the stirring speed is adjusted to 120-140 r / min, and the reaction temperature of the reactor is controlled at 50-55℃.

6. The method for preparing precipitated silica for high-silica formulations according to claim 1, characterized in that, After the water glass solution is added dropwise during the replenishment of the silicon source, the mixture is stirred at a speed of 120-140 r / min for 5-10 min. After stirring, a sample is taken to observe the state of the reaction system.

7. The method for preparing precipitated silica for high-silica formulations according to claim 1, characterized in that, During the acidification process, the dropping rate is controlled at 6-10 mL / min, and the stirring is carried out at a speed of 120-140 r / min, while the reaction temperature is controlled at 50-55℃.

8. The method for preparing precipitated silica for high-silica formulations according to claim 1, characterized in that, The filtration time is controlled at 20-30 min and adjusted appropriately according to the viscosity of the silica precipitate slurry to separate a silica filter cake with a solid content of 20-25%.

9. The method for preparing precipitated silica for high-silica formulations according to claim 1, characterized in that, The filter cake is stirred during the washing process until the conductivity of the filter cake is <100μS / cm, and the sodium sulfate content in the filter cake is determined by the conductivity of the washing water. The washing continues until the sodium sulfate content of the final product is less than 2%.

10. The method for preparing precipitated silica for high-silica formulations according to claim 1, characterized in that, The slurry is fed into an airflow dryer to dry it, and then the dried slurry is pulverized by an airflow pulverizer.

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