Preparation method and application of white carbon black with low water content

Abstract

The invention provides a preparation method and application of white carbon black with low water content, and relates to the technical field of white carbon black preparation, the method comprises the following steps: filtering a sodium silicate solution generated by desiliconization of fly ash or coal gangue to form a desiliconization solution; adding polyethylene glycol and an auxiliary agent A into the desilicication liquid, introducing carbon dioxide into the sodium silicate solution under the conditions of 70 DEG C and 0.2 MPa for carbonation, and carrying out aging treatment; carrying out filter pressing on the slurry, and washing with clear water and acid liquor until the slurry is neutral, wherein the water content of an obtained filter cake is only 50%; the bulk density of the white carbon black is up to about 0.3-0.4 g / cm < 3 >, and compared with the white carbon black prepared by a traditional precipitation method, the white carbon black prepared by the method can greatly reduce the drying and transportation cost. The filtrate produced by the method can be causticized to recover NaOH and calcium carbonate, so that resource recycling is realized. The white carbon black shows high reinforcing property, low heat generation and excellent wear resistance in car tires, off-the-road tires and conveyor belt covering rubber, and is suitable for high-performance rubber products.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, and in particular to a method for preparing low-moisture, high-bulk-density silica and its application. Background Technology

[0002] In the rubber industry, silica is an important reinforcing filler, widely used in energy-saving tires and engineering products. However, the traditional precipitated silica production process mainly uses the reaction of sodium silicate and sulfuric acid. Although the technology is mature, it suffers from problems such as huge washing water volume, high drying energy consumption, and high packaging and transportation costs. For example, the moisture content of traditional precipitated silica is often as high as 75-80%. In order to meet the technical requirements of downstream customers for soluble salts in the product, it is often necessary to use several times the volume of water as filter cake for repeated washing. The washing water volume per ton of silica is usually as high as 15-20 tons, which not only wastes water resources but also generates a large amount of wastewater that needs to be treated. For silica with a moisture content of 75-80%, the natural gas consumption for drying one ton of product is as high as 200 cubic meters, and the drying cost alone is about 600 yuan. In addition, the bulk density of silica produced by the traditional precipitated method is usually less than 0.25 g / cm³. 3 This also results in high packaging and transportation costs. In summary, although traditional precipitated silica is the product with the largest output, widest application, and lowest production cost, its production cost remains high due to limitations in its physicochemical properties, resulting in high filter cake moisture content and low product density. Therefore, there is an urgent need to develop a new type of silica with low moisture content and high bulk density. Summary of the Invention

[0003] The purpose of this invention is to provide a method for preparing low-moisture, high-bulk-density silica and its application, in order to solve the problems in the existing silica products, such as excessively high moisture content, low bulk density, difficulty in filtration and washing due to the formation of gel-like substances during production, and high energy and water consumption. These problems result in high production costs, low efficiency, and significant environmental pressure for silica, and restrict its application in high-end rubber products.

[0004] The specific technical solution of this invention is as follows: This invention provides a method for preparing low-moisture, high-bulk-density silica, comprising the following steps: S1. Preparation of sodium silicate solution: Filter the sodium silicate solution produced by desilication of fly ash or coal gangue; S2, Carbonation reaction: Polyethylene glycol and additive A are added to sodium silicate solution, and carbon dioxide gas is introduced and stirred. When the pH value is 9-10, the gas is stopped, and a dispersant is added for aging to obtain the aged slurry. S3. Post-processing: The aged slurry is subjected to liquid-solid separation by a plate and frame filter press, the filter cake is washed, and the filter cake is placed in a spray drying tower to dry, thereby obtaining low moisture content and high bulk density silica.

[0005] Furthermore, the method also includes S4, byproduct recovery: the filtrate produced by the carbonation reaction is mixed with calcium hydroxide and reacted, and then filtered to obtain NaOH solution and calcium carbonate precipitate.

[0006] Furthermore, the filtrate produced by the carbonation reaction contains sodium carbonate and sodium bicarbonate. The filtrate produced by the carbonation reaction is mixed with calcium hydroxide at a mass ratio of 1:0.6-1, and causticized at 80±5℃ for 0.8-1.2 hours. After filtration, NaOH solution and calcium carbonate precipitate are obtained.

[0007] Further, 90-100 parts by weight of fly ash or coal gangue are reacted with 300-500 parts by weight of sodium hydroxide at 90°C for 3-7 hours, and the resulting solution is obtained by filtration.

[0008] Furthermore, before introducing carbon dioxide gas into the sodium silicate solution, the silicate solution is adjusted with sodium hydroxide, activated silica powder, and water glass to achieve a silica concentration of 100-120 g / L and a modulus of 1.8-2.2.

[0009] Further, 480-500 parts by weight of sodium silicate solution are added to a stirred reactor, along with 0.8-1.5 parts of polyethylene glycol. The mixture is heated to 70°C, and carbon dioxide gas is introduced at a rate of 0.5 L / min at a pressure of 0.2 MPa. The stirring speed is 200 rpm. When the pH of the slurry reaches 9.5, the gas introduction is stopped, and the mixture is aged for 0.5-3 hours to obtain the aged slurry.

[0010] Further, the aged slurry is subjected to liquid-solid separation using a plate and frame filter press at a pressure of 0.6 MPa. The filter cake is washed three times with clean water, each time using water equal to the volume of the filter cake. Then, it is washed with 5% hydrochloric acid until the pH reaches 7.0, and washed once with clean water. After filtration, the filter cake has a moisture content of 50%-60%. The washed filter cake is placed in a spray drying tower and dried under hot air at 400°C until the moisture content is 3.9-4.2%, yielding low-moisture-content, high-bulk-density silica.

[0011] Furthermore, it also includes adding 1-1.2 parts by weight of additive A to S2. The raw materials for preparing additive A include γ-aminopropyltriethoxysilane, polyether-modified silicone oil, tert-butanol, and deionized water. The raw materials for preparing additive A include, by weight, 55-60 parts of γ-aminopropyltriethoxysilane, 28-30 parts of polyether-modified silicone oil, 8-10 parts of tert-butanol, and 16-20 parts of deionized water. The preparation method of additive A includes stirring 55-60 parts by weight of γ-aminopropyltriethoxysilane and 16-20 parts by weight of deionized water at 45-50°C at a stirring rate of 400 rpm for 30 minutes, adding 28-30 parts of polyether-modified silicone oil and 8-10 parts of tert-butanol, emulsifying at 60-65°C under nitrogen protection at a high-speed shearing rate of 500 rpm for 1 hour, and allowing to stand and mature at 40°C for 1.5-2 hours to obtain additive A.

[0012] This invention also provides an application of the low-moisture-content high-bulk-density silica prepared by the aforementioned method, specifically its application in passenger car tire tread rubber. The method involves plasticizing styrene-butadiene rubber and butadiene rubber, adding low-moisture-content high-bulk-density silica, zinc oxide, stearic acid, antioxidant 4020, and microcrystalline wax, and then mixing. Finally, 8% (by weight of silica) of coupling agent Si-69 is added, and the mixture is discharged. After thin-passing, accelerator CBS and sulfur are added, and the mixture is sheeted to obtain the final compound.

[0013] This invention also provides an application of the low-moisture-content, high-bulk-density silica prepared by the aforementioned method, specifically in the application of the low-moisture-content, high-bulk-density silica in the base rubber of engineering machinery tires. The method involves mixing natural rubber and butadiene rubber, then adding low-moisture-content, high-bulk-density silica, carbon black N330, aromatic oil, zinc oxide, stearic acid, antioxidant RD, and antioxidant 4010NA, and finally adding 8% (by weight of) coupling agent Si-75 to the mixture. Rubber, with the addition of accelerator NOBS and sulfur, is sheeted to obtain a compound, which is then vulcanized to obtain the base rubber for the tread of engineering machinery tires; The application of low-moisture-content, high-bulk-density silica in environmentally friendly, high-filler conveyor belt cover rubber involves plasticizing EPDM rubber, adding low-moisture-content, high-bulk-density silica, paraffin oil, zinc oxide, stearic acid, and antioxidant MB in batches, controlling the discharge temperature; adding peroxide DCP and crosslinking agent TAIC, sheeting to obtain a compound, and vulcanizing to obtain the conveyor belt cover rubber.

[0014] The beneficial effects of this invention are as follows: The method and application of preparing low-moisture, high-bulk-density silica provided by this invention, through the multi-step synergy of sodium silicate solution produced by desilication of fly ash or coal gangue—modulus adjustment, carbonization reaction under specific conditions, synergistic aging with polyethylene glycol / auxiliary agent A, and optimized washing and spray drying processes, successfully prepares low-moisture, high-bulk-density silica. The various formulations and process steps of this method synergistically enhance each other: fly ash acid leaching aluminum leaching residue, fly ash or coal gangue provide a low-cost silicon source; the timely addition of polyethylene glycol and auxiliary agent A during the carbonization process works together to modify the surface of silica particles and stabilize their steric hindrance, effectively controlling the particle size and aggregation state of the original particles, thus laying the structural foundation for high bulk density; subsequent precise washing and high-temperature spray drying further reduce the product's moisture content and fix its loose microstructure. When this type of silica is applied to rubber compositions, its low moisture content ensures high reactivity with coupling agents, while its high bulk density gives the rubber compound better processing flowability and dispersibility. The silica, specific coupling agents and rubber matrix produce a synergistic effect, which ultimately makes the vulcanized rubber exhibit significantly better comprehensive performance than conventional silica reinforcement in terms of tensile strength, tear resistance, dynamic heat generation and aging resistance. This meets the stringent requirements of high-performance tires and engineering rubber products for low rolling resistance, high wear resistance and long service life.

[0015] This invention is primarily based on the precise control of nucleation, growth, and aggregation steps in the synthesis of silica (white carbon black) via precipitation. In the carbon fractionation reaction, carbon dioxide is introduced and reacts with a sodium silicate solution to generate silicic acid. The silicic acid molecules rapidly condense to form nanoscale primary particles, which then further aggregate and grow. Polyethylene glycol, added at this stage, acts as a dispersant, preventing excessive aggregation of the primary particles through steric hindrance. Meanwhile, the hydrolysis product of γ-aminopropyltriethoxysilane in additive A can bond with the silanol groups on the surface of the silicic acid particles, introducing organic functional groups. The polyether-modified silicone oil further reduces interfacial tension, improves wettability and dispersion stability, and tert-butanol acts as a co-solvent to promote compatibility among the components. The combined effect of these components, at the levels of silane coupling and polymers and surfactants, effectively regulates the interparticle interactions, guiding the formation of more uniform, dense, and structurally stable secondary aggregates. This determines the high bulk density of the final product. In the subsequent spray drying process, high-temperature hot air instantly evaporates moisture. Because the aforementioned steps have already formed structurally stable aggregates, they are less prone to structural collapse during rapid dehydration, thus better maintaining the internal pore structure and achieving an extremely low final moisture content. In rubber applications, the low moisture content ensures that the silane coupling agent can react efficiently with the hydroxyl groups on the silica surface, reducing coupling agent hydrolysis failure caused by moisture. The high bulk density and good dispersibility make it easier for silica to be wetted and dispersed by rubber polymer chains during mixing, reducing stress concentration points caused by agglomerates. This comprehensively improves the integrity and mechanical properties of the vulcanizate network and reduces heat generation under dynamic use. Detailed Implementation

[0016] The technical solutions in the embodiments of this application are described clearly and completely below. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0017] The surfactant involved in this invention is polyethylene glycol with a molecular weight of 4000. γ-aminopropyltriethoxysilane (KH-550) was purchased from Qufu Jiaye Chemical New Materials Co., Ltd., and the polyether-modified silicone oil is DY-ET204 from Shandong Dayi Chemical Co., Ltd.

[0018] Example 1 This embodiment provides a method for preparing low-moisture, high-bulk-density silica, comprising the following steps: S1. Preparation of sodium silicate solution: 95 parts by weight of coal gangue (particle size of 100 mesh) and 400 parts by weight of 30% sodium hydroxide solution were reacted at 90℃ for 5 hours. After filtration, crude sodium silicate solution was obtained. The solution was adjusted to SiO2 concentration of 110 g / L and modulus of 2.0 with water, water glass and active silica powder. After filtration, sodium silicate solution B was obtained. S2, Carbonation reaction: Add 480 parts by weight of sodium silicate solution B to a stirred reactor, add 0.8 parts of polyethylene glycol and 1 part of additive A, heat to 70°C, introduce 99% carbon dioxide gas at a rate of 0.5 L / min, pressure of 0.2 MPa, stirring speed of 200 rpm, stop gas introduction when pH reaches 9.5, and age for 2.5 hours to obtain aged slurry; S3. Post-treatment: The aged slurry is subjected to liquid-solid separation using a plate and frame filter press at a pressure of 0.6 MPa. The filter cake is washed three times with clean water, each time using water equal to the volume of the filter cake. It is then washed with 5% hydrochloric acid until the pH reaches 7.0, followed by one wash with clean water. The resulting filter cake has a moisture content of 57%. The filter cake is placed in a spray drying tower and dried at 400℃ hot air until the moisture content reaches 4.0%, yielding low-moisture-content, high-bulk-density silica. S4. Byproduct recovery: The filtrate containing sodium carbonate and sodium bicarbonate produced by the carbonation reaction is mixed with calcium hydroxide at a mass ratio of 1:0.8, and causticized at 80°C for 1 hour. After filtration, NaOH solution and calcium carbonate precipitate are obtained.

[0019] The raw materials for preparing Additive A include γ-aminopropyltriethoxysilane, polyether-modified silicone oil, tert-butanol, and deionized water. The raw materials for Additive A, by weight, include 55 parts γ-aminopropyltriethoxysilane, 28 parts polyether-modified silicone oil, 8 parts tert-butanol, and 16 parts deionized water. The preparation method for Additive A includes mixing 55 parts γ-aminopropyltriethoxysilane and 16 parts deionized water at 45°C and a stirring rate of 400 rpm for 30 minutes; adding 28 parts polyether-modified silicone oil and 8 parts tert-butanol; emulsifying at 60°C and nitrogen protection using high-speed shearing at 500 rpm for 1 hour; and allowing to stand and mature at 40°C for 1.5 hours to obtain Additive A.

[0020] Example 2 This embodiment provides a method for preparing low-moisture, high-bulk-density silica, comprising the following steps: S1. Preparation of sodium silicate solution: 100 parts by weight of fly ash (particle size of 100 mesh) and 300 parts by weight of 30% sodium hydroxide solution were reacted at 90°C for 3 hours. After filtration, crude sodium silicate solution was obtained. The solution was adjusted to SiO2 concentration of 120 g / L and modulus of 1.8 with water, water glass and active silica powder. After filtration, sodium silicate solution B was obtained. S2, Carbonation reaction: Add 480 parts by weight of sodium silicate solution B to a stirred reactor, add 0.9 parts of polyethylene glycol and 1.2 parts of additive A, heat to 70°C, introduce 99% carbon dioxide gas at a rate of 0.5 L / min, pressure of 0.2 MPa, stirring speed of 200 rpm, stop gas introduction when pH reaches 9.5, and age for 2.5 hours to obtain aged slurry; S3. Post-treatment: The aged slurry is subjected to liquid-solid separation using a plate and frame filter press at a pressure of 0.6 MPa. The filter cake is washed three times with clean water, each time using water equal to the volume of the filter cake. It is then washed with 5% hydrochloric acid until the pH reaches 7.0, followed by one wash with clean water. The resulting filter cake has a moisture content of 50%. The filter cake is placed in a spray drying tower and dried at 400℃ hot air until the moisture content reaches 3.9%, yielding low-moisture-content, high-bulk-density silica. S4. Byproduct recovery: The filtrate containing sodium carbonate and sodium bicarbonate produced by the carbonation reaction is mixed with calcium hydroxide at a mass ratio of 1:0.8, and causticized at 80°C for 1 hour. After filtration, NaOH solution and calcium carbonate precipitate are obtained.

[0021] The raw materials for preparing additive A include γ-aminopropyltriethoxysilane, polyether-modified silicone oil, tert-butanol, and deionized water. The raw materials for preparing additive A, by weight, include 60 parts of γ-aminopropyltriethoxysilane, 30 parts of polyether-modified silicone oil, 10 parts of tert-butanol, and 20 parts of deionized water. The preparation method of additive A includes stirring 60 parts of γ-aminopropyltriethoxysilane and 20 parts of deionized water at 50°C and a stirring rate of 400 rpm for 30 minutes, adding 30 parts of polyether-modified silicone oil and 10 parts of tert-butanol, emulsifying at 500 rpm at 65°C under nitrogen protection for 1 hour, and allowing to stand and mature at 40°C for 2 hours to obtain additive A.

[0022] Application Example 1 This application example provides an application of Example 1 in passenger car tire tread compound. 75 parts by weight of styrene-butadiene rubber (SBR1502) and 25 parts by weight of butadiene rubber (BR9000) are mixed in an internal mixer and plasticized at an initial temperature of 80°C for 60 seconds. 55 parts by weight of the aforementioned silica, 3 parts by weight of zinc oxide, 2 parts by weight of stearic acid, 2 parts by weight of antioxidant 4020, and 1.5 parts by weight of microcrystalline wax are added, and the mixture is mixed with the top plug for 90 seconds. After cleaning, 8% by weight of coupling agent Si-69 based on the mass of silica is added, and the mixture is mixed for another 90 seconds before discharge. The discharge temperature is controlled at 155°C. The resulting first-stage compound is left to stand at room temperature for 24 hours, then passed through a two-roll mill at a roll temperature of 65°C three times. 1.8 parts by weight of accelerator CBS and 1.5 parts by weight of sulfur are added, and the mixture is cut, formed into triangular bundles, and then sheeted to obtain the final compound. The final compound was placed in a flat vulcanizing machine and vulcanized at 150°C and 15 MPa for 10.5 minutes to obtain vulcanized rubber test pieces. The tensile strength of the vulcanized rubber was tested to be 22.8 MPa, the elongation at break was 485%, the stress at 300% elongation was 12.1 MPa, and the Shore A hardness was 68. The results indicate that the silica-reinforced tread compound of Example 1 has good overall mechanical properties, low heat generation, and is suitable for high-performance passenger car tires requiring low rolling resistance and high wear resistance.

[0023] Application Example 2 This application example provides an application of Example 1 in the base rubber of engineering machinery tire tread. 80 parts by weight of natural rubber (STR20) and 20 parts by weight of butadiene rubber (BR9000) are mixed in an internal mixer at an initial temperature of 70°C and a rotor speed of 45 rpm for 30 seconds. 45 parts by weight of the aforementioned silica, 15 parts by weight of carbon black N330, 8 parts by weight of aromatic oil, 5 parts by weight of zinc oxide, 3 parts by weight of stearic acid, 2 parts by weight of antioxidant RD, and 1.5 parts by weight of antioxidant 4010NA are added, and the mixture is mixed for 120 seconds with the top plug raised. After cleaning, 8% by weight of coupling agent Si-75 based on the mass of silica is added, and the mixture is continued to be mixed for 150 seconds before discharge. The discharge temperature is controlled at 148°C. The resulting compound is left to stand for 24 hours. 0.8 parts by weight of accelerator NOBS and 2.2 parts by weight of sulfur are added on an open mill, mixed evenly, and sheeted. The compound was vulcanized at 143℃ and 20 MPa for 45 minutes to obtain vulcanized rubber samples. Tests showed that the vulcanized rubber had a tensile strength of 25.5 MPa, an elongation at break of 520%, a tear strength of 65 kN / m, and a Goodrich flexural heat rise ΔT of 18℃, exhibiting excellent resistance to cut growth. The results indicate that the silica-reinforced rubber compound of Example 1 possesses high strength, excellent tear resistance, and low dynamic heat generation, meeting the long-life requirements of engineering machinery tires under harsh operating conditions for resistance to chipping and spalling, and low heat generation.

[0024] Application Example 3 This application example provides a second embodiment of the application of a green and environmentally friendly high-filler conveyor belt cover rubber. 100 parts by weight of EPDM (ENB content 5.0%) are mixed in an internal mixer and plasticized for 40 seconds at an initial temperature of 60°C. Subsequently, a total of 120 parts by weight of the aforementioned silica, 60 parts by weight of paraffin oil, 5 parts by weight of zinc oxide, 1 part by weight of stearic acid, and 1 part by weight of antioxidant MB are added in batches, controlling the mixing time of each stage to 100 seconds and the discharge temperature to below 115°C. The resulting first-stage compound is left to stand for 12 hours. Then, 3.5 parts by weight of peroxide DCP and 2 parts by weight of crosslinking agent TAIC are added to an open mill with a roll temperature of 70°C, mixed thoroughly, and sheeted. The compound is then vulcanized at 160°C and 10 MPa for 20 minutes to obtain vulcanized rubber test pieces. The tested vulcanized rubber exhibited a tensile strength of 15.6 MPa, an elongation at break of 350%, and a Shore A hardness of 75. After aging in hot air at 125°C for 72 hours, its tensile strength retention rate reached 92%, and its elongation at break retention rate reached 88%. Furthermore, the compound demonstrated good abrasion resistance and low compression set. The results indicate that even with high filler content, the silica in Example 2 can maintain good processability, excellent overall physical and mechanical properties, and heat aging resistance in the EPDM compound, making it perfectly suitable for heavy-duty conveyor belt cover rubber applications with stringent requirements for durability and environmental friendliness.

[0025] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that in Comparative Example 1, an equal weight of additive A is added after the carbonization is completed and the slurry aging is completed, and the mixture is stirred for 30 minutes. The other contents are the same as in Example 1.

[0026] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that Comparative Example 2 lacks an equal part by weight of polyether-modified silicone oil in Additive A; otherwise, it is the same as Example 1.

[0027] Comparative Example 3 The difference between Comparative Example 3 and Example 1 is that Comparative Example 3 lacks an equal amount of tert-butanol in Additive A, but the rest is the same as Example 1.

[0028] Comparative Example 4 The difference between Comparative Example 4 and Example 1 is that Comparative Example 4 lacks equal parts by weight of polyether-modified silicone oil and tert-butanol in Additive A. Otherwise, it is the same as Example 1.

[0029] Performance testing Bulk density, specific surface area (BET), and activation (hydrophobicity) were tested for the examples and comparative examples. Bulk density was determined according to GB / T 20020-2013 "Fused Silica". Specific surface area was determined according to GB / T 19587-2017 using the nitrogen adsorption method. For the activation test, 2.00 g of sample was weighed, dispersed in 50 mL of deionized water, sonicated for 10 minutes, and then allowed to stand. The mass of powder that sank to the bottom was measured. Activation (%) was calculated as (1 - mass of precipitate / total mass of sample) × 100%. The results are shown in Table 1.

[0030] Table 1. Performance test data of silica in the examples and comparative examples

[0031] As shown in Table 1, the examples have lower bulk density, higher specific surface area, and higher activation. Comparative Example 1 is inferior to Example 1 in all aspects. Additive A, as a structure directing agent, must be added before carbonization. Comparative Example 2 shows increased bulk density and decreased specific surface area. The steric hindrance effect of polyether-modified silicone oil is crucial for forming a low-density, high-specific-surface-area structure. Comparative Example 3 shows decreased activation and increased tanδ. Tert-butanol, as an azeotropic agent, promotes complete silane grafting reaction. Incomplete grafting leads to residual surface polarity, affecting rubber compatibility and dynamic properties. Comparative Example 4 shows slightly worse performance.

[0032] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for preparing low-moisture silica, characterized in that, Includes the following steps: S1. Preparation of sodium silicate solution: Filter the sodium silicate solution produced by desilication of fly ash or coal gangue; S2. Carbonation Reaction: Polyethylene glycol and additive A are added to the sodium silicate solution, and carbon dioxide gas is introduced. The mixture is stirred, and gas introduction is stopped when the pH reaches 9-10. Aging treatment then begins. Additive A is prepared from γ-aminopropyltriethoxysilane, polyether-modified silicone oil, tert-butanol, and deionized water. The raw materials for additive A, by weight, include 55-60 parts γ-aminopropyltriethoxysilane, 28-30 parts polyether-modified silicone oil, 8-10 parts tert-butanol, and 16-2 parts deionized water. The preparation method of the additive A includes mixing 55-60 parts by weight of γ-aminopropyltriethoxysilane and 16-20 parts by weight of deionized water at 45-50°C with a stirring rate of 400 rpm for 30 minutes, adding 28-30 parts by weight of polyether modified silicone oil and 8-10 parts by weight of tert-butanol, emulsifying at 60-65°C under nitrogen protection with high-speed shearing at 500 rpm for 1 hour, and allowing to stand and mature at 40°C for 1.5-2 hours to obtain additive A; S3. Post-processing: The aged slurry is separated into liquid and solid by a plate and frame filter press, the filter cake is washed, and the filter cake is dried in a spray drying tower to obtain low moisture content and high bulk density silica. S4. Byproduct recovery: The filtrate produced by the carbonation reaction is mixed with calcium hydroxide and reacted, then filtered to obtain NaOH solution and calcium carbonate precipitate.

2. The preparation method according to claim 1, characterized in that, The method also includes a filtrate containing sodium carbonate and sodium bicarbonate produced by the carbonation reaction.

3. The preparation method according to claim 1, characterized in that, The filtrate from the carbonation reaction was mixed with calcium hydroxide at a mass ratio of 1:0.6-1, and the mixture was causticized at 80±5℃ for 0.8-1.2 hours. The mixture was then filtered to obtain a NaOH solution and a calcium carbonate precipitate.

4. The preparation method according to claim 1, characterized in that, By weight, 90-100 parts of fly ash or coal gangue and 300-500 parts of sodium hydroxide are reacted at 90°C for 3-7 hours, and the mixture is filtered to obtain a sodium silicate solution.

5. The preparation method according to claim 1, characterized in that, Before introducing carbon dioxide gas into the sodium silicate solution, adjust the sodium silicate solution with sodium hydroxide, activated silica powder, or water glass until the silica concentration is 100-120 g / L and the modulus is 1.8-2.

2.

6. The preparation method according to claim 1, characterized in that, Add 480-500 parts by weight of sodium silicate solution to a stirred reactor, then add 0.8-1.5 parts of polyethylene glycol, heat to 70°C, introduce carbon dioxide gas at a rate of 0.5 L / min, at a pressure of 0.2 MPa, and at a stirring speed of 200 rpm. Stop the gas introduction when the pH of the slurry reaches 9.5, and then let it stand for aging for 0.5-3 hours to obtain the aged slurry.

7. The preparation method according to claim 1, characterized in that, The aged slurry was subjected to liquid-solid separation using a plate and frame filter press at a pressure of 0.6 MPa. The filter cake was washed three times with water, each time using water equal to the volume of the filter cake. Then, it was washed with 5% hydrochloric acid until the pH reached 7.0, and washed once with water. After filtration, the filter cake had a moisture content of 50%-60%. The washed filter cake was placed in a spray drying tower and dried at 400°C with hot air until the moisture content was 3.9-4.2%, yielding low-moisture-content, high-bulk-density silica.

8. The application of silica prepared by the method for preparing low-moisture silica according to any one of claims 1 to 7, characterized in that, The application in passenger car tire tread rubber specifically includes: plasticizing styrene-butadiene rubber and butadiene rubber, adding low moisture content high bulk density silica, zinc oxide, stearic acid, antioxidant 4020 and microcrystalline wax for mixing; adding coupling agent Si-69 based on 8% of silica mass for mixing and discharge, thin-passing, adding accelerator CBS and sulfur, and sheeting to obtain the final compound.

9. The application of a low-moisture-content, high-bulk-density silica prepared by the method for preparing low-moisture-content silica according to any one of claims 1 to 7, characterized in that, The application of low-moisture-content, high-bulk-density silica in the base rubber of engineering machinery tires specifically includes: mixing natural rubber and butadiene rubber, adding low-moisture-content, high-bulk-density silica, carbon black N330, aromatic oil, zinc oxide, stearic acid, antioxidant RD, and antioxidant 4010NA; adding coupling agent Si-75 (based on 8% of silica mass) for compounding and discharge, adding accelerator NOBS and sulfur, sheeting to obtain the compound, and vulcanizing to obtain the base rubber of engineering machinery tire treads; the application of low-moisture-content, high-bulk-density silica in environmentally friendly, high-filler conveyor belt cover rubber involves: plasticizing EPDM rubber, adding low-moisture-content, high-bulk-density silica, paraffin oil, zinc oxide, stearic acid, and antioxidant MB in batches for compounding, controlling the discharge temperature; adding peroxide DCP and crosslinking agent TAIC, sheeting to obtain the compound, and vulcanizing to obtain the conveyor belt cover rubber.

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