Method for preparing precipitated silica for non-slip shoe soles

Abstract

The application discloses a preparation method of precipitated silicon dioxide for antiskid shoe soles, and comprises the following steps: S1, configuring water glass solution and sulfuric acid solution; S2, adding the sulfuric acid solution and the water glass solution into deionized water to react, controlling the adding amount and the reaction temperature with time change, forming a three-stage reaction process, and respectively performing initial aging operation; S3, adjusting the pH value to 4.5-6.5; S4, continuously stirring to perform later aging; S5, after the later aging is completed, the reaction liquid is prepared into slurry after pressure filtration and washing; and S6, the slurry is spray dried to obtain silicon dioxide particles, and the silicon dioxide particles are smashed and packed. In the adding reaction process of the sulfuric acid solution and the water glass solution, the reaction is controlled into three stages, and the pH value is adjusted in different stages, so that the generated precipitated primary particle size and aggregate structure can be adjusted and controlled, and meanwhile, the initial aging operation is additionally arranged in each stage, and the reaction in each stage is further stabilized.

Description

Technical Field

[0001] This invention relates to the field of silica preparation, and in particular to a method for preparing precipitated silica for anti-slip shoe soles. Background Technology

[0002] Shoes play multiple important roles in daily life and work. Their primary function is protection, effectively isolating the feet from direct contact with the outside world, preventing accidental injuries from stones and glass shards, and reducing the risk of bacterial and viral infections. Different groups have diverse needs when choosing shoes based on age, activity level, and health conditions. These needs primarily focus on comfort, functionality, safety, and durability. Children and adolescents, as a growing and developing group, require shoes with breathable and cushioning materials to reduce the risk of sports injuries. Adult sports enthusiasts prioritize versatility and adaptability, including balanced cushioning, support, slip resistance, and breathability in athletic shoes. The elderly prioritize slip resistance, lightweight design, and foot support, with shoes featuring soles that enhance traction to prevent slipping indoors or in the rain.

[0003] Precipitated silica is currently the mainstream choice for sports shoes and casual shoes due to its low cost and balanced reinforcement effect, offering numerous performance advantages. However, existing precipitation methods for preparing silica often employ single or stepwise pH control during the reaction stage. In actual preparation, the precipitation effect varies under different pH conditions due to the fusion reaction of raw materials. This single or stepwise pH control method makes it impossible to regulate the primary particle size, aggregate structure, and surface silanol distribution of the resulting product particles during the fusion reaction, leading to a decrease in the elasticity and anti-slip properties of the obtained silica product. Therefore, this paper proposes a method for preparing precipitated silica for anti-slip shoe soles to solve the above problems. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing precipitated silica for anti-slip shoe soles, 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 anti-slip shoe soles, comprising the following steps:

[0006] S1, First, prepare a water glass solution and select sulfuric acid solution as the acidifying agent; S2, add the sulfuric acid solution and water glass solution prepared in S1 to heated deionized water and stir to react. During the stirring process, control the amount of sulfuric acid solution and water glass solution added and the reaction temperature over time to form a three-stage reaction process, and perform initial aging operations in the corresponding stages. S3, after the stirring reaction is complete, stop adding water glass solution, then continue adding sulfuric acid solution to adjust the pH value to 4.5-6.5, and then stop adding sulfuric acid solution; S4, continue stirring for later aging; S5, after the later aging process, the reaction solution is filtered and washed to make a slurry; S6. After spray drying the slurry, silica particles are obtained, which are then crushed and packaged.

[0007] Preferably, the concentration of the water glass solution is 20-25 wt%, and the acidifying agent is prepared by diluting 98% sulfuric acid solution to a 10%-20% sulfuric acid solution.

[0008] Preferably, the operation steps of S2 are as follows: first, add one-sixth to one-fifth of the volume of deionized water to the reactor; then heat the deionized water with steam; then add the prepared water glass solution and sulfuric acid solution and stir; and continue the three-stage addition reaction until the reaction solution reaches two-thirds to three-quarters of the reactor volume.

[0009] Preferably, the temperature of the steam-heated deionized water is 95℃-100℃, and the three-stage reaction intervals are respectively controlled as the first stage 0-10min interval, the second stage 10-30min interval, and the third stage 30-55min interval, and the stirring speed during each stage of the reaction is controlled at 100-200r / min.

[0010] Preferably, the reaction time after adding water glass solution and sulfuric acid solution in the first stage is controlled within the range of 0-8 min of the total reaction time, and the initial aging time of the first stage is within the range of 8-10 min of the total reaction time. The reaction time after adding water glass solution and sulfuric acid solution in the second stage is controlled within the range of 10-25 min of the total reaction time, and the initial aging time of the first stage is within the range of 25-30 min of the total reaction time. The reaction time after adding water glass solution and sulfuric acid solution in the third stage is controlled within the range of 30-45 minutes of the total reaction time, while the initial aging time of the first stage is within the range of 45-55 minutes of the total reaction time.

[0011] Preferably, the first stage reaction has a pH of 10-11 and a reaction temperature of 95℃-100℃, the second stage reaction has a pH of 8-9 and a reaction temperature of 85℃-90℃, and the third stage reaction has a pH of 10-11 and a reaction temperature of 95℃-100℃.

[0012] Preferably, the sulfuric acid solution is added in step S3 for 10-15 minutes, and the mixture is stirred at a speed of 100-200 r / min during the addition of the sulfuric acid solution, while the pH is monitored in real time. At the same time, the temperature is controlled at 85℃-95℃ by steam heating during the pH adjustment process.

[0013] Preferably, the time for the later aging operation in step S4 is 10-20 minutes, and the stirring speed is controlled at 100-200 r / min during the aging process.

[0014] Preferably, after the late-stage aging in step S5, a reactive hydraulic filtration is first performed at 0.4-0.8 MPa; During the pressure filtration process, deionized water at a temperature of 50℃-70℃ is used for washing. When the conductivity of the washed water is measured to be 200-800 μS / cm during the washing process, the sodium sulfate content in the finished product is less than 2%. After washing, the resulting filter cake is fed into a pulping machine, and deionized water is added to make a slurry. The solid content of the slurry is adjusted to 20%-25%.

[0015] Preferably, the operation of step S6 is as follows: the slurry prepared in S5 is spray-dried at an inlet air temperature of 450℃-550℃ and an outlet air temperature of 110℃-130℃ to obtain silica particles, and the water content of the silica particles is 5%-7%; then the obtained silica particles are crushed by airflow and then screened and packaged.

[0016] The technical effects and advantages of this invention are as follows: In this invention, the reaction process involving the addition of sulfuric acid solution and water glass solution is controlled in three stages. Different pH values ​​are adjusted at different stages by controlling the amount of raw materials added. This allows for the adjustment and control of the initial particle size and aggregate structure of the generated precipitate. In addition, an initial aging operation is added at each stage to further stabilize the reaction at each stage, ensuring that the final product has a good surface silanol distribution, thereby improving the anti-slip performance of the final product. Attached Figure Description

[0017] Figure 1 This is a flowchart illustrating the operation 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 anti-slip shoe soles, as shown, includes the following steps: S1. First, prepare a water glass solution and select sulfuric acid solution as the acidifying agent. The concentration of the water glass solution is 20-25 wt%. The acidifying agent is prepared by diluting 98% sulfuric acid solution to 10%-20% sulfuric acid solution. The water glass solution is the silicon source in this scheme. In the actual preparation process, sodium silicate with a modulus of 3.1-3.4 is taken and diluted and adjusted with deionized water. Based on the SiO2 content, the concentration of the prepared water glass solution is 20-25 wt%. The concentration range of 20%-25% can ensure that there are enough silicate groups participating in the reaction system, and can also avoid excessive local viscosity or premature gelation due to excessive concentration, thus ensuring the fluid dynamic stability during the co-current reaction. In the actual operation and processing, in order to avoid the interference of impurities on the subsequent production process, the prepared water glass solution is filtered. The filtration can be carried out using a filter cartridge with a diameter of less than five micrometers to remove insoluble residues, gel particles and metal impurities from the prepared water glass solution. When preparing the acidifying agent, 98% concentrated sulfuric acid is slowly and gradually added to room-temperature deionized water while stirring. During the dilution process, the temperature is controlled at 60°C by heat dissipation. The final solution obtained is a sulfuric acid solution with a concentration of 10%–20%. This concentration range of sulfuric acid solution can provide stable H+. + The release rate was determined, and the reaction precipitation was carried out in accordance with the concentration of the prepared water glass solution.

[0020] S2, add the sulfuric acid solution and water glass solution prepared in S1 to heated deionized water and stir to react. During the stirring process, control the amount of sulfuric acid solution and water glass solution added and the reaction temperature over time to form a three-stage reaction process, and perform initial aging operations in the corresponding stages. Specifically, the S2 operation steps are as follows: First, add one-sixth to one-fifth of the reactor volume of deionized water as the base liquid; then heat the deionized water with steam, and then add the prepared water glass solution and sulfuric acid solution and stir. The reaction is carried out in three stages until the reaction liquid reaches two-thirds to three-quarters of the reactor volume and then it is stopped. The temperature of the deionized water is heated by steam to 95℃-100℃. The three-stage reaction time is controlled in the following intervals: the first stage is 0-10 min, the second stage is 10-30 min, and the third stage is 30-55 min. The stirring speed during each stage of the reaction is controlled at 100-200 r / min. The stirring is carried out by a slanted blade turbine or propeller impeller to ensure that the fluid in the reactor forms turbulence and prevent local overheating or over-acidification. Under the stirring in this speed range, the bubbles and vortices generated by the reaction of raw materials in the reactor are eliminated, ensuring that the newly added sulfuric acid solution and water glass solution can be dispersed in the shortest possible time. Furthermore, in the first stage reaction, the reaction time after adding water glass solution and sulfuric acid solution is controlled within the 0-8 min range of the total reaction time. The initial aging time of the first stage is within the 8-10 min range of the total reaction time. The pH value of the first stage reaction is 10-11, and the reaction temperature is 95℃-100℃. Under strong alkalinity and high temperature, silicate ions rapidly polymerize to form a large number of uniform initial crystal nuclei, resulting in a product with a high specific surface area. In the first stage aging treatment, feeding is stopped, and only stirring and temperature are maintained to allow the surface of the initial crystal nuclei generated in the first stage to condense and rearrange, eliminating surface defects and preventing abnormally large particles from appearing in subsequent growth. In an environment with pH > 10, silicic acid ions ionize... The presence of silicate ions in the form of nuclei increases the concentration of silicate ions per unit volume. At temperatures above 95°C, the thermodynamic energy required for nucleation is provided, allowing silicate to aggregate in a short time, forming a large number of initial crystal nuclei. Due to the short-term aggregation, the silicon resources that can be combined by a large number of initial crystal nuclei are limited, which in turn limits the growth of individual particles and ultimately leads to a high specific surface area of ​​the product. During the feeding reaction stage, crystal nuclei may develop surface defects or form amorphous agglomerates due to collisions or rapid growth. When feeding is stopped and the aging process begins, small particles with high surface energy and sharp edges in the reaction will dissolve, and silicon resources will be redeposited on the surface of large and stable crystal nuclei. This prevents the silicon resources deposited on the crystal nuclei from becoming abnormally large particles too quickly, ensuring the uniformity of subsequent growth.

[0021] The second-stage reaction, after adding water glass and sulfuric acid solutions, was controlled within the total reaction time range of 10-25 minutes. The initial aging period of the first stage was within the total reaction time range of 25-30 minutes. The pH value of the second-stage reaction was 8-9, and the reaction temperature was 85℃-90℃. Under the conditions of the second stage, the particles generated in the first stage no longer focused on formation but on connection, constructing chain aggregates through surface condensation reactions. In the second-stage reaction, as the pH and temperature decreased and approached the isoelectric point, the electrostatic repulsion between particles weakened, and primary particles formed chain aggregates through surface silanol condensation. The aggregates form chain-like and branched structures to enhance the anti-slip properties of the final product. In the second-stage aging process, the aggregates are kept at a constant temperature to strengthen the Si-O-Si bonds within them, resulting in a more stable network structure that is less prone to breakage during post-processing. During the second-stage reaction, while the isoelectric point of silica is between pH 2 and 3, in a water glass solution containing sodium ions, controlling the pH to 8 and 9 reduces the surface charge of the crystal nuclei generated in the first stage, weakening the electrostatic repulsion between particles. This causes the crystal nuclei generated in the first stage to attract, collide, and adhere to each other, forming chain-like structures. The aggregates are dendritic or three-dimensional network-like. In the second stage, the temperature is lowered to reduce the molecular thermal energy and prevent particles from violently colliding and bouncing apart, thus facilitating crystal nucleation and chain formation. The lowering temperature also slows down the condensation reaction rate, allowing the crystal nuclei time to find suitable connection sites and form a more stable bonded structure. The second stage employs aging treatment because the connection points between particles are fragile immediately after aggregation. Aging allows the silanol groups at the connection points to undergo dehydration condensation, forming stable siloxane bonds. After aging, the aggregates are then subjected to further filtration, drying, and air jet milling processes. In the first stage, the product resists shear forces and retains high structural integrity, thus ensuring that the produced product provides beneficial tear resistance and elasticity in rubber products, thereby providing a basis for anti-slip. Based on this operation, the generated rubber product forms a three-dimensional network support, increasing the deformation resistance and hysteresis loss when the sole contacts the ground, and improving anti-slip performance. In the second stage of feeding, the addition rate of sulfuric acid solution exceeds that of water glass solution, and by controlling the acidification rate, the pH is effectively reduced while avoiding local over-acidification and the formation of silica lumps. Therefore, the stirring rate should be maintained at 100-200 r / min in the second stage.

[0022] The reaction time in the third stage, after adding water glass solution and sulfuric acid solution, is controlled within the total reaction time range of 30-45 minutes. The initial aging time in the first stage is within the total reaction time range of 45-55 minutes. The pH value of the third stage reaction is 10-11, and the reaction temperature is 95℃-100℃. By adjusting the pH and temperature, the surface of the aggregates is etched in an alkaline environment to increase the density of surface silanol groups and improve surface activity. In the aging treatment of the third stage, the final surface hydroxylation modification is completed, and the surface charge of the particles is homogenized, preparing the structure for subsequent acid washing and transformation. Because there are unstable and high-energy silicon-oxygen bonds on the surface of the aggregates formed in the second stage reaction, the silicon-oxygen bonds will undergo reversible hydrolysis in an alkaline and high-temperature environment. The reaction expression is as follows: During the hydrolysis process, irregular protrusions on the surface are continuously eroded away, leaving isolated silanol groups on the surface, which increases the surface hydroxyl density of silica. In the third stage of aging treatment, after the reactions of the first two stages, the charge states of different aggregates are different. Aging in an alkaline environment, the silanol groups on the particle surface undergo final rearrangement and ionization, making the surface charge of all particles tend to be consistent. At the same time, after the third stage of aging treatment, the uniform surface charge generates a strong electrostatic repulsion force, ensuring that the silica particles are stably suspended in the slurry and preventing irreversible hard agglomeration during subsequent acidification and washing.

[0023] In this scheme, the three-stage aging treatment in step S2 ensures that the reactions at each stage reach equilibrium, guaranteeing the continuous and stable reaction process. This also produces product particles with a narrow particle size distribution, improving the anti-slip properties of the manufactured rubber products. After the stirring reaction in step S3 is complete, stop adding water glass solution and then continue adding sulfuric acid solution to adjust the pH to 4.5-6.5. Stop adding sulfuric acid solution after this adjustment. The sulfuric acid solution should be added for 1-15 minutes, with stirring at 100-200 rpm and real-time pH monitoring. During pH adjustment, the temperature should be controlled at 85℃-95℃ using steam heating. After the third stage of reaction in step S2 is complete, the particle surface is uniformly coated with negative charges. In an alkaline environment, the particles are free in the solution due to electrostatic repulsion. When sulfuric acid solution is added in this step to lower the pH, the negative charges on the particle surface are gradually converted by H+. + Neutralization occurs when the surface properties of particles are uneven. After losing electrostatic repulsion, these particles will collide and stick together to form hard agglomerates. These hard agglomerates cannot be dispersed by stirring and can be granulated and crushed to form products. At the same time, in a weakly acidic environment, the residual sodium ions exist in ionic form, which are highly soluble in water, and the particle surface no longer adsorbs sodium ions, thus improving the efficiency of subsequent washing to remove sodium ions.

[0024] S4 involves continuous stirring for post-aging. The post-aging process in S4 lasts 1-20 minutes, with the stirring speed controlled at 100-200 rpm. After the acidification treatment in S3, under weak acid and high temperature conditions, small particles and irregular surface protrusions continue to dissolve, and the silicon source is further deposited on the surface of large particles, ensuring a narrower particle size distribution and a smoother particle surface. Furthermore, after S3, the particle surface is filled with newly formed, unstable Si-OH bonds. The heat-preserving aging in S4 promotes the dehydration and condensation between these groups, strengthening the skeletal strength within the aggregates and ensuring they are not broken during subsequent pressure filtration and pulverization. The post-aging process in S4 also helps the residual sodium ions encapsulated within the aggregates diffuse and release into the liquid phase, facilitating subsequent washing operations.

[0025] After the final aging stage (S5), the reaction solution is filtered and washed to form a slurry. In step S5, after the final aging stage, the reaction solution is first subjected to hydraulic filtration at a pressure of 0.4-0.8 MPa. Under a constant pressure of 0.4-0.8 MPa, the reaction solution is squeezed through the filter cloth, solid silica is trapped to form a filter cake, while the liquid byproduct sodium sulfate is discharged with the water. This pressure range is chosen to balance efficiency and quality: too low a pressure will result in slow filtration speed and low capacity; too high a pressure will over-compact the filter cake. During the filter press process, deionized water at a temperature of 50℃-70℃ is used for washing. Hot deionized water at 50-70℃ is used during washing because the increased temperature significantly reduces the viscosity of the water and increases the solubility of sodium sulfate, thereby greatly improving the mass transfer efficiency. Salt is washed away with less water and in a shorter time. When the conductivity of the washed water is 200-800μS / cm, the sodium sulfate content in the finished product is less than 2%. The conductivity of the solution is directly proportional to the concentration of ions in it. By monitoring the conductivity of the outflowing water online in real time, the residual salt content in the water can be known instantly. By controlling the conductivity at 200-800μS / cm, the sodium sulfate content in the filter cake is locked at less than 2%, which prevents the subsequent rubber products made from the product from blooming, water absorption slippage, or abnormal vulcanization caused by residual impurities. After washing, the resulting filter cake is fed into a pulping machine, where deionized water is added to form a slurry. The solid content of the slurry is adjusted to 20%–25%. If the solid content is below 20%, too much water will enter the spray drying stage, resulting in energy waste and the product is prone to dust formation. If the solid content is above 25%, the slurry viscosity will be too high, making pumping difficult and increasing the risk of atomizer clogging, while also making it difficult to atomize evenly. Therefore, the 20%–25% range ensures that the slurry has good fluidity while allowing the spray drying process to achieve the best balance between energy consumption and molding quality, ultimately producing a granular finished product with good fluidity and no hard agglomerates. S6 involves spray drying the slurry to obtain silica particles, which are then crushed and packaged. The operation of step S6 is as follows: the slurry prepared in S5 is spray dried at an inlet air temperature of 450℃-550℃ and an outlet air temperature of 110℃-130℃ to obtain silica particles. The moisture content of the silica particles is 5%-7%. The outlet air temperature directly reflects the drying intensity and can accurately lock the moisture content of the finished product at 5%-7%. Then, the obtained silica particles are crushed by airflow and then screened and packaged. The slurry with a solid content of 20%-25% prepared by S5 is pumped to an atomizer at the top of a spray drying tower via a high-pressure pump. The slurry is atomized into droplets of tens of micrometers, which come into instantaneous contact with the 450-550℃ high-temperature natural gas hot air entering from the top or bottom. This vaporizes the moisture on the surface of the droplets and forces the moisture inside the droplets to be expelled, leaving tiny pores inside the dried silica particles, ultimately forming a hollow or porous microsphere structure. This structure gives the product excellent flowability and low bulk density, making it easy to disperse in rubber. Silica powder collected from the bottom of the drying tower is fed into an air jet mill, where the high-speed airflow generates strong impact and shearing forces to break up the aggregates. The powder is then sieved through a vibrating screen to remove large particles. This sieving process ensures that the final product has a concentrated particle size distribution, with no particles exceeding the screening diameter.

[0026] As a comparative example, silica was prepared by precipitation using a stepwise decrease in pH. The performance of the silica product prepared by this method is compared with that of the silica product prepared in this method, as shown in Table 1 below. Table 1 Product Performance Comparison Table

[0027] The comparison in the table above clearly shows that this method, through multi-stage pH control combined with reaction time and reactive temperature control, achieves superior performance across the board. The toad-like flakes prepared using this method enhance the physical and mechanical properties of the shoe sole. Silica, as a reinforcing filler, effectively improves the abrasion resistance, hardness, tensile strength, and tear strength of the sole. Its porous structure and high dispersibility help fill the pores of the rubber matrix, making the material denser, thereby improving overall compressive strength and durability. Silica also improves the processing performance of the shoe sole, enhancing the flowability and uniformity of the sole compound, strengthening its adhesion to the rubber matrix, reducing cracking or peeling problems during production, optimizing mold filling effects, improving production efficiency and finished product quality stability, and its fine particles also increase surface roughness, improve the coefficient of friction, and enhance anti-slip performance. This project has developed a special precipitated silica product for shoe soles, which can endow the sole with excellent comprehensive performance.

[0028] 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 for anti-slip shoe soles, characterized in that, The following steps are included: S1, First, prepare a water glass solution and select sulfuric acid solution as the acidifying agent; S2, add the sulfuric acid solution and water glass solution prepared in S1 to heated deionized water and stir to react. During the stirring process, control the amount of sulfuric acid solution and water glass solution added and the reaction temperature over time to form a three-stage reaction process, and perform initial aging operations in the corresponding stages. S3, after the stirring reaction is complete, stop adding water glass solution, then continue adding sulfuric acid solution to adjust the pH value to 4.5-6.5, and then stop adding sulfuric acid solution; S4, continue stirring for later aging; S5, after the later aging process, the reaction solution is filtered and washed to make a slurry; S6. After spray drying the slurry, silica particles are obtained, which are then crushed and packaged.

2. The method for preparing precipitated silica for anti-slip shoe soles according to claim 1, characterized in that, The concentration of the water glass solution is 20-25 wt%, and the acidifying agent is prepared by diluting 98% sulfuric acid solution to a 10%-20% sulfuric acid solution.

3. The method for preparing precipitated silica for anti-slip shoe soles according to claim 1, characterized in that, The operation steps of S2 are as follows: First, add one-sixth to one-fifth of the volume of the reactor to the reactor. Then, heat the deionized water with steam. After that, add the prepared water glass solution and sulfuric acid solution and stir. The reaction is carried out in three stages until the reaction solution reaches two-thirds to three-quarters of the reactor volume and then stops.

4. The method for preparing precipitated silica for anti-slip shoe soles according to claim 3, characterized in that, The temperature of the deionized water is heated by steam to 95℃-100℃. The three-stage reaction is controlled within the following time intervals: the first stage is 0-10 min, the second stage is 10-30 min, and the third stage is 30-55 min. The stirring speed during each stage of the reaction is controlled at 100-200 r / min.

5. The method for preparing precipitated silica for anti-slip shoe soles according to claim 4, characterized in that, The reaction time after adding water glass solution and sulfuric acid solution in the first stage is controlled within the range of 0-8 minutes of the total reaction time. The initial aging time of the first stage is within the range of 8-10 minutes of the total reaction time. The reaction time after adding water glass solution and sulfuric acid solution in the second stage is controlled within the range of 10-25 min of the total reaction time, and the initial aging time of the first stage is within the range of 25-30 min of the total reaction time. The reaction time after adding water glass solution and sulfuric acid solution in the third stage is controlled within the range of 30-45 minutes of the total reaction time, while the initial aging time of the first stage is within the range of 45-55 minutes of the total reaction time.

6. The method for preparing precipitated silica for anti-slip shoe soles according to claim 5, characterized in that, The first stage reaction has a pH of 10-11 and a reaction temperature of 95℃-100℃, the second stage reaction has a pH of 8-9 and a reaction temperature of 85℃-90℃, and the third stage reaction has a pH of 10-11 and a reaction temperature of 95℃-100℃.

7. The method for preparing precipitated silica for anti-slip shoe soles according to claim 1, characterized in that, The sulfuric acid solution is added in S3 for 10-15 minutes, and the mixture is stirred at a speed of 100-200 r / min during the addition process. The pH is monitored in real time, and the temperature is controlled at 85℃-95℃ by steam heating during the pH adjustment process.

8. The method for preparing precipitated silica for anti-slip shoe soles according to claim 1, characterized in that, The duration of the later aging operation in step S4 is 10-20 minutes, and the stirring speed is controlled at 100-200 r / min during the aging process.

9. The method for preparing precipitated silica for anti-slip shoe soles according to claim 1, characterized in that, After the late-stage aging process in step S5 is completed, a reaction hydraulic filtration is first performed at 0.4-0.8 MPa. During the pressure filtration process, deionized water at a temperature of 50℃-70℃ is used for washing. When the conductivity of the washed water is measured to be 200-800 μS / cm during the washing process, the sodium sulfate content in the finished product is less than 2%. After washing, the resulting filter cake is fed into a pulping machine, and deionized water is added to make a slurry. The solid content of the slurry is adjusted to 20%-25%.

10. The method for preparing precipitated silica for anti-slip shoe soles according to claim 1, characterized in that, The operation of step S6 is as follows: the slurry prepared in S5 is spray-dried at an inlet air temperature of 450℃-550℃ and an outlet air temperature of 110℃-130℃ to obtain silica particles with a water content of 5%-7%; then the obtained silica particles are crushed by airflow and then screened and packaged.

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