Preparation method of hydrated silicon dioxide for preventing particle agglomeration

Abstract

The present invention relates to the technical field of highly dispersed hydrated silica for silicone rubber, and in particular to a method for preparing hydrated silica that prevents particle agglomeration. During the reaction process, the present invention uses a silane hydrolyzate to effectively disperse and modify newly generated silica particles, effectively preventing particle agglomeration and greatly reducing the content of surface hydroxyl groups. At the same time, a high-speed stirring method is adopted to effectively solve the "local over-concentration" phenomenon of the reaction materials and greatly reduce the generation of gel. The step-by-step acidification technology makes the particle distribution more uniform. The addition of a dispersion modifier with specific components and proportions in the pulping process effectively reduces particle agglomeration during the drying process. Through the above technical means, the product indicators of the present invention are effectively reduced in DET / CTAB, surface hydroxyl content, ignition loss, DBP absorption value, particle size distribution width, etc. compared with existing hydrated silica products for silicone rubber, thereby greatly improving the dispersibility of the product in silicone rubber.

Description

[0001] This invention is a divisional application of the parent application with application number 202210561496.4, application date 20220523, and titled "A Method for Preparing Highly Dispersed Hydrated Silica for Silicone Rubber". Technical Field

[0002] The invention relates to the technical field of highly dispersed hydrated silicon dioxide for silicone rubber, and in particular to a preparation method of hydrated silicon dioxide capable of preventing particle agglomeration. Background Art

[0003] Silicone rubber boasts excellent high and low temperature resistance, weather resistance, hydrophobicity, electrical insulation, and physiological inertness. It is widely used in defense and military applications, electronics, healthcare, industry, agriculture, and daily life. With the rapid development of the silicone industry in recent years, the demand for hydrated silica as a reinforcing agent has continued to grow.

[0004] Hydrated silica, commonly known as precipitated white carbon black, contains a large number of hydroxyl groups on its surface, making it highly hydrophilic. Due to its large surface area, hydrated silica tends to aggregate secondary to its surroundings. Furthermore, it readily absorbs moisture from the air, which leads to strong hydrogen bonding between the hydroxyl groups, further enhancing the cohesion between the particles. During the synthesis reaction, gel formation is common due to local overconcentration of the reactants. This gel content significantly affects the dispersibility of the product in silicone rubber. Furthermore, the silica particles formed during the reaction are prone to agglomeration, resulting in an uneven particle size distribution. These factors make mixing and dispersion difficult in silicone rubber. Furthermore, when mixed in large quantities, gel formation is also common, causing the rubber to harden and generating significant heat during mixing. To achieve optimal dispersion, ultrafinely ground silica is currently commonly used in silicone rubber products. However, the ultrafine product has fine particles and a light bulk density, which increases packaging, storage, and transportation costs. Furthermore, during ultrafine processing and customer use, dust is generated, and powder absorption is slow during rubber mixing, requiring multiple additions. This method results in long mixing times (generally over 5 hours). This method has a long mixing time, high energy consumption, and low efficiency. These factors limit its application in high-demand silicone rubber. Therefore, the development and production of highly dispersed silica for silicone rubber with good dispersibility and a narrow particle size distribution without ultrafine grinding has broad market prospects.

[0005] The technical problems or technical bottlenecks that need to be solved urgently are first to control the production of gel during the reaction process and reduce the agglomeration of SiO2 particles, so as to obtain a product with uniform particle size distribution; secondly, to select the preferred additives to partially modify the product during the production process, reduce the surface hydroxyl content of the product, so as to improve its dispersibility and reinforcement performance in silicone rubber. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a method for preparing hydrated silicon dioxide that prevents particle agglomeration, thereby improving the dispersibility and reinforcing properties of hydrated silicon dioxide and making the prepared hydrated silicon dioxide product suitable for the field of silicone rubber products without ultrafine grinding.

[0007] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0008] A method for preparing hydrated silicon dioxide for preventing particle agglomeration comprises the following steps:

[0009] Step 1: Preparation of reaction materials, including:

[0010] The silane coupling agent is added to a hydrolyzate prepared by mixing water and polyols in advance and hydrolyzed to obtain a silane hydrolyzate C; the mass ratio of the silane coupling agent, water and polyols is 1:4-6:2;

[0011] Sodium silicate and water are mixed uniformly in a mass ratio of 1:0.1-0.7, filtered through a plate and frame filter press and a bag filter, and then added with silane hydrolyzate C to obtain sodium silicate solution A for reaction; the concentration of Na2O in sodium silicate solution A is 0.85-1.24 mol / L;

[0012] Concentrated sulfuric acid, water and inorganic salt dispersant are mixed evenly at a ratio of 1:4-6:0.001-0.003 and then filtered through a precision ceramic filter element to obtain a sulfuric acid solution B for reaction with a concentration of 18-30%;

[0013] Step 2: Place 25-30m 3 Water is added to the reactor, heated to 80-95°C with saturated steam, and 0.8-1.5 ml of water is added at a stirring speed of 60-80 r / h. 3 After the pH value of sodium silicate solution A is measured to be within the range of 9-10.6, sodium silicate solution A and sulfuric acid solution B are added into the reactor at the same time at a flow rate of 3.5-2.0:1. The pH value is controlled within the range of 10-11, the temperature is controlled within the range of 85-95°C, and the reaction is carried out for 95-105 minutes.

[0014] Step 3: After the reaction is completed, adjust the flow rate of sulfuric acid solution B to 60-70% of the reaction acid flow rate, acidify until the material pH is within the range of 9±0.2, stop adding acid, and homogenize for 10-15 minutes. Then adjust the acid flow rate to 50-60% of the reaction acid flow rate, acidify until the material pH is within the range of 6±0.2, and homogenize for 10-15 minutes. Finally, adjust the acid flow rate to 40-50% of the reaction acid flow rate, acidify until the material pH is within the range of 4±0.2, stop adding acid, and homogenize for 30-40 minutes;

[0015] Step 4: Pump the homogenized material into a plate and frame filter press, and then wash with water until the effluent conductivity is ≤350μs / cm;

[0016] Step 5: After being fully washed, the filter cake is conveyed to a slurry tank by a belt conveyor, and a dispersant modifier of 0.1-0.5% of the product weight is added. The filter cake is stirred at high speed to form a slurry with a viscosity of ≤600cps.

[0017] Step 6: Dry the slurry by spray drying to obtain a highly dispersed hydrated silica product for silicone rubber.

[0018] Furthermore, in the above-mentioned method for preparing hydrated silicon dioxide for preventing particle agglomeration, the silane coupling agent is selected from one of HMDS and KH550, or a combination of the two.

[0019] Furthermore, in the above method for preparing hydrated silicon dioxide for preventing particle agglomeration, the polyol is selected from n-butanol or glycerol.

[0020] Furthermore, in the above-mentioned method for preparing hydrated silicon dioxide for preventing particle agglomeration, the dispersion modifier is prepared by compounding raw materials with a mass ratio of HT5050: polyethylene glycol 400: water = 1:2:5.

[0021] Furthermore, in the above-mentioned method for preparing hydrated silicon dioxide for preventing particle agglomeration, in step 1, sodium silicate is prepared by the following method:

[0022] Low-iron solid water glass and water are added to a hydrostatic autoclave in a specific proportion. 0.7 MPa steam is introduced to dissolve the solution, and the pressure is maintained for 2-2.5 hours. The solution is then placed in a storage tank and allowed to stand for at least 24 hours before being filtered using a plate and frame filter press. After filtration, sodium silicate is obtained. The iron content of the solid water glass is ≤120 ppm, and the conductivity of the water is ≤100 μs / cm.

[0023] Furthermore, in the above-mentioned method for preparing hydrated silicon dioxide for preventing particle agglomeration, in step 1, the concentrated sulfuric acid is highly transparent concentrated sulfuric acid with a transparency of ≥200 mm.

[0024] Furthermore, in the above-mentioned method for preparing hydrated silicon dioxide for preventing particle agglomeration, in step 1, the inorganic salt dispersant is selected from one or both of sodium sulfate and sodium hexametaphosphate.

[0025] The present invention also protects a highly dispersed hydrated silicon dioxide product for silicone rubber obtained by the above-mentioned method for preparing hydrated silicon dioxide for preventing particle agglomeration.

[0026] The beneficial effects of the present invention are as follows: the present invention uses silane hydrolyzate to effectively disperse and modify the newly generated silica particles during the reaction process, effectively preventing the agglomeration of the particles and greatly reducing the content of hydroxyl groups on their surface. At the same time, the high-speed stirring method is adopted to effectively solve the phenomenon of "local over-concentration" of the reaction materials, greatly reducing the generation of gel. The step-by-step acidification technology makes the particle distribution more uniform. The addition of a dispersion modifier with specific components and proportions in the pulping process effectively reduces the agglomeration of particles during the drying process. Through the above technical means, the product indicators of the present invention are compared with the existing hydrated silica products for silicone rubber, such as DET / CTAB, surface hydroxyl content, ignition loss, DBP absorption value, particle size distribution width, etc., which greatly improves the dispersibility of the product in silicone rubber. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a laser particle size distribution diagram of the highly dispersed hydrated silicon dioxide for silicone rubber prepared in Example 1 of the present invention;

[0028] Figure 2 This is a laser particle size distribution diagram of the highly dispersed hydrated silicon dioxide for silicone rubber prepared in Example 2 of the present invention;

[0029] Figure 3 This is a laser particle size distribution diagram of the highly dispersed hydrated silicon dioxide for silicone rubber prepared in Example 3 of the present invention;

[0030] Figure 4 This is a laser particle size distribution diagram of the highly dispersed hydrated silicon dioxide for silicone rubber prepared in Comparative Example 1 of the present invention;

[0031] Figure 5 This is the laser particle size distribution diagram of the highly dispersed hydrated silicon dioxide for silicone rubber prepared in Comparative Example 2 of the present invention. DETAILED DESCRIPTION

[0032] To illustrate the technical content, achieved objectives and effects of the present invention in detail, the following description is given in conjunction with the embodiments and accompanying drawings.

[0033] The present invention relates to a method for preparing hydrated silicon dioxide for preventing particle agglomeration, comprising the following steps:

[0034] Step 1: Preparation of reaction materials, including:

[0035] A silane coupling agent is added to a hydrolyzate prepared by mixing water and a polyol, and hydrolyzed to obtain a silane hydrolyzate C; the silane coupling agent is selected from one or a combination of HMDS and KH550, and the polyol is n-butanol or glycerol; the mass ratio of the silane coupling agent, water, and polyol is 1:4-6:2;

[0036] Low-iron solid water glass (iron content ≤ 120 ppm) and purified process water (conductivity ≤ 100 μs / cm) are added to an autoclave in a certain proportion, and 0.7 MPa steam is introduced for dissolution, maintaining the pressure for 2-2.5 hours. The solution is then placed in a storage tank and allowed to stand for at least 24 hours before being filtered using a plate-and-frame filter press. The filtered sodium silicate is then mixed with the purified process water in a mass ratio of 1:0.1-0.7, filtered through a plate-and-frame filter press and a bag filter, and then pumped into a storage tank. Silane hydrolyzate C is then added under stirring to obtain sodium silicate solution A for the reaction. The concentration of Na2O in sodium silicate solution A is 0.85-1.24 mol / L.

[0037] Concentrated sulfuric acid is selected and filtered through a secondary precision ceramic filter element to obtain highly permeable concentrated sulfuric acid with a transparency of ≥200 mm; the highly permeable concentrated sulfuric acid is uniformly mixed with purified process water and an inorganic salt dispersant at a ratio of 1:4-6:0.001-0.003, and then filtered through a precision ceramic filter element to obtain a sulfuric acid solution B for reaction with a concentration of 18-30%; the inorganic salt dispersant is selected from one or both of sodium sulfate and sodium hexametaphosphate;

[0038] Step 2: Place 25-30m 3 Add the purified process water into the reactor, heat it to 80-95℃ with saturated steam, and add 0.8-1.5m 3 After the pH value of sodium silicate solution A is measured to be within the range of 9-10.6, sodium silicate solution A and sulfuric acid solution B are added into the reactor at the same time at a flow rate of 3.5-2.0:1. The pH value is controlled within the range of 10-11, the temperature is controlled within the range of 85-95°C, and the reaction is carried out for 95-105 minutes.

[0039] Step 3: After the reaction is completed, adjust the flow rate of sulfuric acid solution B to 60-70% of the reaction acid flow rate, acidify until the material pH is within the range of 9±0.2, stop adding acid, and homogenize for 10-15 minutes. Then adjust the acid flow rate to 50-60% of the reaction acid flow rate, acidify until the material pH is within the range of 6±0.2, and homogenize for 10-15 minutes. Finally, adjust the acid flow rate to 40-50% of the reaction acid flow rate, acidify until the material pH is within the range of 4±0.2, stop adding acid, and homogenize for 30-40 minutes;

[0040] Step 4: Pump the homogenized material into a plate and frame filter press, and then wash with purified process water until the effluent conductivity is ≤350μs / cm;

[0041] Step 5: After being fully washed, the filter cake is conveyed to a slurry tank by a belt conveyor, and a dispersing modifier (prepared in a ratio of sodium polycarboxylate HT5050: polyethylene glycol 400: water = 1:2:5) is added at 0.1-0.5% of the product weight. The filter cake is stirred at high speed to form a slurry with a viscosity of ≤600 cps.

[0042] Step 6: Dry the slurry by spray drying, and control the heating loss within the range of 5-7% to obtain a highly dispersed hydrated silica product for silicone rubber.

[0043] Example 1

[0044] A method for preparing hydrated silicon dioxide for preventing particle agglomeration comprises the following steps:

[0045] Step 1: Preparation of reaction materials, including:

[0046] 10.5 kg HMDS was added to 50 kg 10% propylene glycol solution and hydrolyzed at room temperature for 20 min under stirring to obtain silane hydrolyzate C;

[0047] Take 7t low iron solid water glass (iron content ≤ 120ppm) and 14m 3 Purified process water (conductivity ≤ 100μs / cm) was added to an autoclave, and 0.7MPa steam was introduced for dissolution, maintaining the pressure for 2.5 hours. The solution was then placed in a storage tank and allowed to stand for at least 24 hours before being filtered using a plate-and-frame filter press. The resulting sodium silicate was then mixed with the purified process water in a mass ratio of 1:0.4, filtered through a plate-and-frame filter press and a bag filter, and then pumped into a storage tank. Silane hydrolyzate C was then added under stirring to obtain sodium silicate solution A for the reaction. The concentration of Na2O in sodium silicate solution A was 0.86mol / L.

[0048] Select concentrated sulfuric acid and filter it through a secondary precision ceramic filter element to obtain high-transparency concentrated sulfuric acid with a transparency of ≥200mm; take 2m 3 Highly concentrated sulfuric acid was slowly added with stirring to 16.7 mL 3 Then, 10 kg of anhydrous sodium sulfate was added to the purified process water, mixed evenly, and filtered through a precision ceramic filter element to obtain sulfuric acid solution B for reaction with a concentration of 18.2%;

[0049] Step 2: Convert 26m 3 Purified process water was added into the reactor and heated to 85℃ with saturated steam. Then 1.3m 3 The pH of sodium silicate solution A was measured at 10.5, and the flow rate of sodium silicate solution A was 13m 3 / h, sulfuric acid solution B at a flow rate of 5.3m 3 / h was added into the reactor at the same time, the process was controlled at pH 10.6, the temperature was controlled at 85°C, and the reaction was carried out for 105 minutes;

[0050] Step 3: After the reaction is completed, close the valve of sodium silicate solution A and adjust the acid flow rate to 3.18m 3 / h, acidify until the pH of the material is 9.06, stop adding acid, homogenize for 15 minutes; then adjust the acid flow rate to 2.91m 3 / h, acidify until the pH of the material is 6.02, and homogenize for 12 minutes. Finally, adjust the acid flow rate to 2.22m 3 / h, acidify until the pH of the material is 4.16, stop adding acid, and homogenize for 35 minutes;

[0051] Step 4: Pump the homogenized material into a plate and frame filter press, and then wash it with purified process water until the effluent conductivity reaches 330μs / cm;

[0052] Step 5: The fully washed filter cake is conveyed to a slurry tank by a belt conveyor, and 3.2 kg of a dispersant modifier (prepared in a ratio of sodium polycarboxylate HT5050: polyethylene glycol 400: water = 1:2:5) is added. The filter cake is stirred at high speed to form a slurry with a viscosity of 562 cps.

[0053] Step 6: Dry the slurry by spray drying, and control the heating loss within the range of 5-7% to obtain a highly dispersed hydrated silica product for silicone rubber.

[0054] Example 2

[0055] A method for preparing hydrated silicon dioxide for preventing particle agglomeration comprises the following steps:

[0056] Step 1: Preparation of reaction materials, including:

[0057] 10.5 kg HMDS was added to 50 kg 10% propylene glycol solution and hydrolyzed at room temperature for 20 min under stirring to obtain silane hydrolyzate C;

[0058] Take 7t low iron solid water glass (iron content ≤ 120ppm) and 14m 3 Purified process water (conductivity ≤ 50μs / cm) was added to an autoclave, and 0.7MPa steam was introduced for dissolution, maintaining the pressure for 2.5 hours. The solution was then placed in a storage tank and allowed to stand for at least 24 hours before being filtered using a plate-and-frame filter press. The resulting sodium silicate was then mixed with the purified process water in a mass ratio of 1:0.4, filtered through a plate-and-frame filter press and a bag filter, and then pumped into a storage tank. Silane hydrolyzate C was then added under stirring to obtain sodium silicate solution A for the reaction. The concentration of Na2O in sodium silicate solution A was 1.0mol / L.

[0059] Select concentrated sulfuric acid and filter it through a secondary precision ceramic filter element to obtain high-transparency concentrated sulfuric acid with a transparency of ≥200mm; take 2m 3 Highly concentrated sulfuric acid, slowly add 11m 3Then, 3.5 kg of anhydrous sodium sulfate and 3.5 kg of sodium hexametaphosphate were added to the purified process water, mixed evenly, and filtered through a precision ceramic filter element to obtain sulfuric acid solution B for reaction, with a concentration of 24.93%;

[0060] Step 2: 26.5m 3 Purified process water was added into the reactor and heated to 88℃ with saturated steam. Then 1.14m 3 The pH of sodium silicate solution A was measured at 10.6, and the flow rate of sodium silicate solution A was 11.18m 3 / h, sulfuric acid solution B at a flow rate of 3.72m 3 / h was added into the reactor at the same time, the process was controlled at pH 10.5, the temperature was controlled at 88°C, and the reaction was carried out for 105 minutes;

[0061] Step 3: After the reaction is completed, close the valve A of the sodium silicate solution and adjust the acid flow rate to 2.42m 3 / h, acidify until the pH of the material is 9.01, stop adding acid, and homogenize for 15 minutes. Then adjust the acid flow rate to 2.05m 3 / h, acidify until the pH of the material is 5.96, homogenize for 12 minutes; finally, adjust the acid flow rate to 1.68m 3 / h, acidify until the pH of the material is 4.13, stop adding acid, and homogenize for 35 minutes;

[0062] Step 4: Pump the homogenized material into a plate and frame filter press and then wash with purified process water until the effluent conductivity reaches 326μs / cm;

[0063] Step 5: The fully washed filter cake is conveyed to a slurry tank by a belt conveyor, and 3.2 kg of a dispersant modifier (prepared in a ratio of sodium polycarboxylate HT5050: polyethylene glycol 400: water = 1:2:5) is added. The filter cake is stirred at high speed to form a slurry with a viscosity of 556 cps.

[0064] Step 6: Dry the slurry by spray drying, and control the heating loss within the range of 5-7% to obtain a highly dispersed hydrated silica product for silicone rubber.

[0065] Example 3

[0066] A method for preparing hydrated silicon dioxide for preventing particle agglomeration comprises the following steps:

[0067] Step 1: Preparation of reaction materials, including:

[0068] 6.5 kg HMDS and 3.5 kg KH550 were added to 48 kg of a solution prepared by mixing n-butanol, glycerol, and water in a mass ratio of 1:1:6, and hydrolyzed at room temperature for 20 minutes under stirring to obtain silane hydrolyzate C.

[0069] Take 7t low iron solid water glass (iron content ≤ 120ppm) and 14m 3 Purified process water (conductivity ≤ 50μs / cm) was added to an autoclave, and 0.7MPa steam was introduced for dissolution, maintaining the pressure for 2.5 hours. The solution was then placed in a storage tank and allowed to stand for at least 24 hours before being filtered using a plate-and-frame filter press. The resulting sodium silicate was then mixed with the purified process water in a mass ratio of 1:0.4, filtered through a plate-and-frame filter press and a bag filter, and then pumped into a storage tank. Silane hydrolyzate C was then added under stirring to obtain sodium silicate solution A for the reaction. The concentration of Na2O in sodium silicate solution A was 1.20mol / L.

[0070] Select concentrated sulfuric acid and filter it through a secondary precision ceramic filter element to obtain high-transparency concentrated sulfuric acid with a transparency of ≥200mm; take 2m 3 Highly concentrated sulfuric acid, slowly add 8m 3 Then, 5 kg of anhydrous sodium sulfate was added to the purified process water, mixed evenly, and filtered through a precision ceramic filter element to obtain sulfuric acid solution B for reaction with a concentration of 29.8%;

[0071] Step 2: Convert 28m 3 Add 60m3 of purified process water 3 In the reactor, saturated steam was used to heat the reactor to 90°C, and 0.9 m 3 Sodium silicate solution A, sampled and measured pH 10.6, according to the flow rate of sodium silicate solution A 9.32m 3 / h, sulfuric acid solution B flow rate 2.79m 3 / h were added to the reaction at the same time, the pH was controlled within the range of 10.6±0.2, the temperature was controlled within the range of 90±0.5℃, and the reaction was carried out for 95min;

[0072] Step 3: After the reaction is completed, close the valve A of the sodium silicate solution and adjust the acid flow rate to 1.84m 3 / h, acidify until the pH of the material is 8.97, stop adding acid, and homogenize for 15 minutes. Then adjust the acid flow rate to 1.56m 3 / h, acidify until the pH of the material is 6.05, and homogenize for 12 minutes. Finally, adjust the acid flow rate to 1.30m 3 / h, acidify until the pH of the material is 4.11, stop adding acid, and homogenize for 35 minutes;

[0073] Step 4: Pump the homogenized material into a plate and frame filter press and then wash with purified process water until the effluent conductivity reaches 312 μs / cm;

[0074] Step 5: The fully washed filter cake is conveyed to a slurry tank by a belt conveyor, and 3.2 kg of a dispersant modifier (prepared in a ratio of sodium polycarboxylate HT5050: polyethylene glycol 400: water = 1:2:5) is added. The filter cake is stirred at high speed to form a slurry with a viscosity of 552 cps.

[0075] Step 6: Dry the slurry by spray drying, and control the heating loss within the range of 5-7% to obtain a highly dispersed hydrated silica product for silicone rubber.

[0076] Comparative Example 1

[0077] A method for preparing hydrated silicon dioxide for preventing particle agglomeration comprises the following steps:

[0078] Step 1: Preparation of reaction materials, including:

[0079] Take 7t low iron solid water glass (iron content ≤ 120ppm) and 14m 3 Purified process water (conductivity ≤ 50μs / cm) was added to an autoclave, and 0.7MPa steam was introduced for dissolution, maintaining the pressure for 2.5 hours. The solution was then placed in a storage tank and allowed to stand for at least 24 hours before being filtered using a plate and frame filter press. The resulting sodium silicate was then mixed with the purified process water at a mass ratio of 1:0.4, filtered through a plate and frame filter press and a bag filter, and then pumped into a storage tank to obtain sodium silicate solution A for the reaction. The concentration of Na2O in sodium silicate solution A was 1.0mol / L.

[0080] Select concentrated sulfuric acid and filter it through a secondary precision ceramic filter element to obtain high-transparency concentrated sulfuric acid with a transparency of ≥200mm; take 2m 3 Highly concentrated sulfuric acid was slowly added with stirring to 16.7 mL 3 Then, 3.5 kg of anhydrous sodium sulfate and 3.5 kg of sodium hexametaphosphate were added to the purified process water, mixed evenly, and filtered through a precision ceramic filter element to obtain sulfuric acid solution B for reaction with a concentration of 18.2%;

[0081] Step 2: 26.5m 3 Purified process water was added into the reactor and heated to 88℃ with saturated steam. Then 1.14m 3 The pH of sodium silicate solution A was measured at 10.6, and the flow rate of sodium silicate solution A was 11.18m 3 / h, sulfuric acid solution B at a flow rate of 3.72m 3 / h was added into the reactor at the same time, the process was controlled at pH 10.5, the temperature was controlled at 88°C, and the reaction was carried out for 105 minutes;

[0082] Step 3: After the reaction is completed, close the valve of sodium silicate solution A and adjust the acid flow rate to 3.18m 3 / h, acidify until the pH of the material is 4.09, stop adding acid, and homogenize for 35 minutes;

[0083] Step 4: Pump the homogenized material into a plate and frame filter press and then wash with purified process water until the effluent conductivity reaches 335μs / cm;

[0084] Step 5: After being fully washed, the filter cake is conveyed to a slurry tank by a belt conveyor, and high-speed stirring is used to make the block filter cake into a slurry with a viscosity of 556 cps;

[0085] Step 6: Dry the slurry by spray drying, and control the heating loss within the range of 5-7% to obtain a highly dispersed hydrated silica product for silicone rubber.

[0086] Comparative Example 2

[0087] A method for preparing hydrated silicon dioxide for preventing particle agglomeration comprises the following steps:

[0088] Step 1: Preparation of reaction materials, including:

[0089] Take 7t low iron solid water glass (iron content ≤ 120ppm) and 14m 3 Purified process water (conductivity ≤ 50μs / cm) was added to an autoclave, dissolved by steam at 0.7MPa, and maintained at this pressure for 2.5 hours. The solution was then placed in a storage tank and allowed to stand for at least 24 hours before being filtered using a plate and frame filter press. The resulting sodium silicate was then mixed with the purified process water at a mass ratio of 1:0.4, filtered through a plate and frame filter press and a bag filter, and then pumped into a storage tank to obtain sodium silicate solution A for the reaction. The concentration of Na2O in sodium silicate solution A was 1.20mol / L.

[0090] Select concentrated sulfuric acid and filter it through a secondary precision ceramic filter element to obtain high-transparency concentrated sulfuric acid with a transparency of ≥200mm; take 2m 3 Highly concentrated sulfuric acid, slowly add 8m 3 Then, 3.5 kg of anhydrous sodium sulfate and 3.5 kg of sodium hexametaphosphate were added to the purified process water, mixed evenly, and filtered through a precision ceramic filter element to obtain a sulfuric acid solution B for reaction with a concentration of 29.5%;

[0091] Step 2: Convert 28m 3 Add 60m3 of purified process water 3 In the reactor, saturated steam was used to heat the reactor to 90°C, and 0.9 m 3 Sodium silicate solution A, sampled and measured pH 10.65, according to the flow rate of sodium silicate solution A 9.32m 3 / h, sulfuric acid solution B flow rate 2.79m 3 / h were added to the reaction at the same time, the pH was controlled within the range of 10.6±0.2, the temperature was controlled within the range of 90±0.5℃, and the reaction was carried out for 95min;

[0092] Step 3: After the reaction is completed, close the valve of sodium silicate solution A and adjust the acid flow rate to 3.18m 3 / h, acidify until the pH of the material is 4.13, stop adding acid, and homogenize for 35 minutes;

[0093] Step 4: Pump the homogenized material into a plate and frame filter press and then wash with purified process water until the effluent conductivity reaches 331 μs / cm;

[0094] Step 5: After being fully washed, the filter cake is conveyed to a slurry tank by a belt conveyor, and high-speed stirring is used to make the block filter cake into a slurry with a viscosity of 563 cps;

[0095] Step 6: Dry the slurry by spray drying, and control the heating loss within the range of 5-7% to obtain a highly dispersed hydrated silica product for silicone rubber.

[0096] Table 1 is a comparison of the main quality indicators of the hydrated silicon dioxide products prepared in Examples 1-3 and Comparative Examples 1-2.

[0097] Table 1

[0098]

[0099]

[0100] As shown in Table 1 and Figures 1 to 5 As shown, the present invention uses silane hydrolyzate to effectively disperse and modify the newly generated silica particles during the reaction process, effectively preventing the particles from agglomerating and greatly reducing the content of surface hydroxyl groups. At the same time, the use of high-speed stirring effectively solves the phenomenon of "local over-concentration" of the reaction materials and greatly reduces the generation of gel. The step-by-step acidification technology makes the particle distribution more uniform. The addition of a dispersion modifier with specific components and proportions in the pulping process effectively reduces the agglomeration of particles during the drying process. Through the above technical means, the product indicators of the present invention are effectively reduced in terms of DET / CTAB, surface hydroxyl content, ignition loss, DBP absorption value, particle size distribution width, etc. compared with the existing silicone rubber hydrated silica products, thereby greatly improving the dispersibility of the product in silicone rubber.

[0101] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent transformations made using the contents of the present invention specification, or directly or indirectly applied in related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A method for preparing hydrated silicon dioxide for preventing particle agglomeration, characterized in that: The following steps are included: 1: Preparation of reaction materials, including: adding a silane coupling agent to a hydrolyzate prepared by mixing water and a polyol in advance for hydrolysis to obtain a silane hydrolyzate solution C; the mass ratio of the silane coupling agent, water and polyol is 1:4-6:2; sodium silicate and water are mixed at a mass ratio of 1:0.1-0.7, filtered through a plate and frame filter press and a bag filter, and then added with the silane hydrolyzate solution C to obtain a sodium silicate solution A for reaction; the concentration of Na2O in the sodium silicate solution A is 0.85-1.24 mol / L; concentrated sulfuric acid, water and an inorganic salt dispersant are mixed at a mass ratio of 1:4-6:0.001-0.003, and then filtered through a precision ceramic filter element to obtain a sulfuric acid solution B for reaction with a concentration of 18-30%; step 2: 25-30m 3 Water is added to the reactor, heated to 80-95°C with saturated steam, and 0.8-1.5 ml of water is added at a stirring speed of 60-80 r / h. 3 After sampling and measuring the pH value in the range of 9-10.6, sodium silicate solution A and sulfuric acid solution B are added to the reactor at a flow rate of 3.5-2.0:

1. The pH value is controlled in the range of 10-11, the temperature is controlled in the range of 85-95°C, and the reaction is carried out for 95-105 minutes. Step 3: After the reaction is completed, the flow rate of sulfuric acid solution B is adjusted to 60-70% of the reaction acid flow rate, acidified to a pH value of 9±0.2, the addition of acid is stopped, and the mixture is homogenized for 10-15 minutes. Then, the acid flow rate is adjusted to 50-60% of the reaction acid flow rate, acidified to a pH value of 6±0.2, and the mixture is homogenized for 10-15 minutes. Finally, the acid flow rate is adjusted to a pH value of 6±0.

2. 40-50%, acidify until the pH value of the material is within the range of 4±0.2, stop adding acid, and homogenize for 30-40 minutes; step 4: pump the homogenized material into a plate and frame filter press, and then wash with water until the effluent conductivity is ≤350μs / cm; step 5: convey the fully washed filter cake to a slurry tank by a belt conveyor, and simultaneously add 0.1-0.5% of a dispersant modifier based on the weight of the product, and use high-speed stirring to make the block filter cake into a slurry with a viscosity of 556cps; step 6: dry the slurry by spray drying to obtain a highly dispersed hydrated silica product for silicone rubber; the dispersant modifier is prepared by compounding raw materials with a mass ratio of HT5050: polyethylene glycol 400: water = 1:2:5; The silane coupling agent is selected from HMDS; The polyol is selected from glycerol.

2. The method for preparing hydrated silicon dioxide for preventing particle agglomeration according to claim 1, wherein: In step 1, sodium silicate is prepared by the following method: low-iron solid water glass and water are added to a hydrostatic autoclave in a certain proportion, 0.7 MPa steam is introduced for dissolution, the pressure is maintained for 2-2.5 hours, and then the mixture is placed in a storage tank and allowed to stand for more than 24 hours, and filtered using a plate and frame filter press; sodium silicate is obtained after filtration; the iron content of the solid water glass is ≤120 ppm; and the electrical conductivity of the water is ≤100 μs / cm.

3. The method for preparing hydrated silicon dioxide for preventing particle agglomeration according to claim 1, wherein: In the step 1, the concentrated sulfuric acid is highly transparent concentrated sulfuric acid with a transparency of ≥200 mm.

4. The method for preparing hydrated silicon dioxide for preventing particle agglomeration according to claim 1, wherein: In step 1, the inorganic salt dispersant is selected from one or both of sodium sulfate and sodium hexametaphosphate.

5. A highly dispersed hydrated silicon dioxide product for silicone rubber obtained by the method for preparing hydrated silicon dioxide for preventing particle agglomeration according to any one of claims 1 to 4.

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