Production method of silicon dioxide for indoor vulcanized silicone rubber

Abstract

The invention discloses a production method of silicon dioxide for indoor vulcanized silicone rubber, and belongs to the technical field of silicon dioxide preparation, the production method comprises the following steps: S1, raw material preparation: preparing a sodium silicate solution with the concentration of 1-2 mol / L; preparing a sulfuric acid solution with the concentration of 12-35%; preparing a surfactant mixed solution; preparing modified silicone oil; an absolute ethyl alcohol solution; s2, adding 5m < 3 >-8m < 3 > of pure water into a reaction kettle, heating to 80-95 DEG C by using saturated steam, adding 1m < 3 >-3m < 3 > of the sodium silicate solution prepared in the step S1 under the condition that the stirring speed is 500rpm / min, then adding 100kg-300kg of anhydrous sodium sulfate, stirring for 10-15 minutes, and detecting that the pH value is in a range of 9-10.5; modified silicone oil similar to a base material in structure is selected as a modified material through surface modification, and compared with a coupling agent, the silicone oil is more beneficial to the characteristic of fast powder feeding in the kneading and stirring processes as the silicone oil has diluting and lubricating effects on a main material in the product kneading process, and the compatibility of the powder and the base material is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of silicon dioxide preparation, and in particular relates to a method for producing silicon dioxide for indoor vulcanized silicone rubber. Background Art

[0002] Room temperature vulcanized silicone rubber (RTV) is a new type of silicone elastomer introduced in the 1960s. Its most notable feature is its ability to cure in situ at room temperature without the need for heating or negative pressure, making it extremely convenient to use. As a result, it quickly became a key component of the silicone product portfolio. Today, RTV silicone rubber is widely used in adhesives, sealants, protective coatings, potting, and molding materials across a wide range of industries. Due to its low molecular weight, RTV silicone rubber is often referred to as liquid silicone rubber. Its physical form is typically a flowable fluid or a viscous paste. The fillers used in RTV silicone rubber are similar to those used in HTV silicone rubber, with silica used as a reinforcing agent to effectively enhance the physical properties of the silicone rubber.

[0003] Condensation-type room temperature vulcanized silicone rubber products are primarily composed of base rubber, silicone oil, filler reinforcement, crosslinking agent, and coupling agent. High-end products use fumed silica as the reinforcement, while low-end products often use light or heavy calcium carbonate as filler instead. Fumed silica, due to its high specific surface area and low water content, can effectively combine with the base material through coupling and crosslinking agents after modification to achieve excellent physical properties. However, it is expensive. Precipitated silica, on the other hand, has the following disadvantages that prevent its application in room temperature vulcanized silicone rubber:

[0004] 1. Condensation-type room temperature vulcanized silicone rubber products are mainly composed of base rubber, silicone oil, filler reinforcement, crosslinking agent, and coupling agent. The reinforcement agent used in high-end products is silica produced by the fumed process, while low-end products often use light or heavy calcium carbonate as a filler instead. Due to the high specific surface area and low water content of fumed silica, after modification, it can be effectively combined with the base material through coupling agents and crosslinking agents to achieve its excellent physical properties, but it is expensive.

[0005] 2. The product fineness is difficult to meet the requirements, and the glue is prone to granularity after being made;

[0006] 3. It is difficult to be compatible with the base rubber, and it is necessary to select suitable materials for surface modification. For this purpose, we propose a method for producing silica for indoor vulcanized silicone rubber. Summary of the Invention

[0007] The present invention provides a method for producing silica for indoor vulcanized silicone rubber to solve the problems raised in the above background technology.

[0008] To achieve the above object, the present invention provides the following technical solution: a method for producing silica for indoor vulcanized silicone rubber, comprising the following steps:

[0009] S1. Raw material preparation: prepare sodium silicate solution with a concentration of 1mol / L to 2mol / L; prepare sulfuric acid solution with a concentration of 12% to 35%; prepare surfactant mixture; prepare modified silicone oil; prepare anhydrous ethanol solution;

[0010] S2, 5m 3 ~8m 3 Pure water was added to the reactor and heated to 80℃~95℃ with saturated steam. Then 1m 3 ~3m 3 The sodium silicate solution prepared in step S1 is then added with 100 kg to 300 kg of anhydrous sodium sulfate, stirred for 10 min to 15 min, and the pH value is detected to be in the range of 9 to 10.5;

[0011] S3, the sodium silicate solution prepared in step S1 is added dropwise into the reactor at a flow rate of 8m 3 / h~12m 3 / h, the sulfuric acid solution prepared in step S1 was added dropwise into the reactor, and the flow rate was controlled at 3m 3 / h~5m 3 / h, the pH value during the reaction is controlled within the range of pH9.5 to pH10.5, the temperature is controlled within the range of 85°C to 95°C, and the reaction time is 50min to 80min;

[0012] S4. After the reaction in step S3 is completed, stirring for 10 min to 15 min at a stirring speed of 800 rpm / min to 1000 rpm / min;

[0013] S5, adding the sulfuric acid solution prepared in step S1 to the reactor three times, acidifying the material to a pH range of 4.5 to pH 5.5, then stopping the acid addition and homogenizing the solution in the reactor;

[0014] S6. After the homogenization in step S5 is completed, the material flows out of the cooling tank through the pump and is pumped into the plate and frame filter press for filtration and washing. When the conductivity of the washing water reaches <300 μs / cm, the washing is stopped and extrusion is performed. After the extrusion is completed, dry compressed gas is used for air blowing for 2 min to 5 min, and then the solvent storage tank pump is started. The material is circulated and flushed with an alcohol solvent for 3 min to 5 min. After flushing, the alcohol solvent is collected in a dedicated storage tank. The solvent circulation flushing process in step S6 is subjected to two air blowing processes;

[0015] S7. After the solvent circulation flushing in step S6 is completed, the material obtained in step S6 is beaten, and a surfactant mixture is added during the beating process, with the amount of the mixture added being 1% to 3% of the mass of the material; after the beating is completed, the material is dried using a spray drying tower, and the dried material is collected into an intermediate silo and then conveyed to the intermediate feed hopper by a twin-screw vacuum conveyor at the lower end of the silo;

[0016] S8, the material is transported from the intermediate feed hopper to the fluidized bed for drying. The fluidized bed temperature is set at 800°C to 850°C, the drying time is controlled at 5s to 10s, and the outlet temperature is set at 105°C to 110°C;

[0017] S9. The outlet pipe of the fluidized bed dryer is sprayed with silicone oil diluent by spraying, and the surface of the dry powder is modified with the silicone oil diluent; the material is then transported to the air flow crusher, and the high-temperature air flow is used to crush the material to 6μm to 8μm, thereby obtaining a condensation-type room temperature vulcanized silicone rubber silica product.

[0018] Furthermore, in step S1, when preparing a sodium silicate solution with a concentration of 1 to 2 mol / L, solid sodium silicate with a modulus of 3.0 to 3.3 is selected, dissolved at high temperature and then precipitated, the supernatant is filtered and mixed with pure water, the stirring speed of the stirrer is 300 r / min to 500 r / min, the stirring time is 30 min to 60 min, and the liquid is adjusted to the corresponding molarity; when preparing a sulfuric acid solution with a concentration of 12% to 35%, a sulfuric acid solution with a concentration of 98% is mixed with pure water at 100 r / min. The mixture is stirred at a speed of 100-200 r / min and then filtered through a precision ceramic filter element; a surfactant, wherein the surfactant is one of sodium lauryl sulfate, stearate and polyethylene glycol or a mixture thereof; a modified silicone oil, wherein the modified material is a silane coupling agent and a modified silicone oil, and the modified material is added with an alcoholysis solution prepared by compounding the modified material with an alcohol solution in advance to obtain a silane coupling agent and a modified silicone oil alcoholysis solution; the modified material is preferably modified silicone oil polyether modified polydimethylsiloxane, the alcohol is preferably ethanol, and the mass ratio of the modified silicone oil to ethanol is 1:30-50 for use as powder surface modification.

[0019] Furthermore, in step S2, when the temperature reaches 80°C, the temperature is slowly increased at a rate of 2°C / min to 95°C.

[0020] Furthermore, in step S3, when the sodium silicate solution is added dropwise, a filter is installed on the dropping pipeline; during the reaction period of 50 to 80 minutes, the reaction solution is sampled every 10 minutes, and the reaction progress is detected by titration.

[0021] Furthermore, in step S4, by setting sampling ports at different heights and positions of the reactor, the reaction solution is sampled once every 5 minutes during the stirring time of the reactor to ensure that the materials in the reactor are evenly stirred.

[0022] Furthermore, in step S5, the sulfuric acid solution prepared in step S1 is added dropwise for the first time, and the flow rate is adjusted to 1m 3 / h~3m 3 / h, acidify until the pH of the material is within the range of 8.5-9.5. Stop adding acid and homogenize for 10-15 minutes;

[0023] The sulfuric acid solution prepared in step S1 was added dropwise for the second time, and the flow rate was adjusted to 1m 3 / h~3m 3 / h, acidify until the pH of the material is within the range of 7.5-8.5. Stop adding acid and homogenize for 10-15 minutes;

[0024] The sulfuric acid solution prepared in step S1 was added dropwise for the third time, and the flow rate was adjusted to 1m 3 / h~3m 3 / h, acidify to the pH range of 4.5 to pH 5.5, stop adding acid, and homogenize for 15min to 40min.

[0025] Furthermore, in step S6, during the filter pressing process, the pressure is gradually increased, with the initial pressure being 0.1 MPa to 0.2 MPa, and then pressurized to 0.3 MPa to 0.5 MPa; when deionized water is used for washing, the temperature of the deionized water for washing is controlled at 20° C. to 25° C.

[0026] Furthermore, in step S7, the viscosity of the slurry is controlled at <550cps; the temperature in the drying tower is controlled at 420°C to 450°C, the outlet temperature is controlled at 105°C to 110°C, and the time the powder stays in the tower is controlled at 10s to 20s; the conveying length of the twin-screw vacuum conveyor is 1m to 3m, and the vacuum degree is -0.4Mpa to 0.6Mpa.

[0027] Furthermore, in step S9, the gas temperature in the high-temperature air flow crusher is 180° C. to 220° C., the flow rate is 30 m / s to 50 m / s, and the pressure of the air flow is 0.8 MPa to 1.2 MPa.

[0028] The beneficial effects of the present invention are:

[0029] 1. The present invention selects modified silicone oil with a structure similar to that of the base material as the modified material through surface modification. Since silicone oil plays a diluting and lubricating role on the main material during the product kneading process, compared with coupling agent, silicone oil is more conducive to the characteristic of fast powder absorption during kneading and stirring, and the compatibility of powder and base material.

[0030] 2. This method effectively dries the particles by replacing water molecules with alcohol molecules, followed by drying at ambient pressure and medium temperature, and vacuum extraction of volatiles to remove water. This effectively dries the particles by replacing the alcohol molecules. Finally, high-temperature airflow drying evaporates any remaining moisture within the pores of the particles. The material is then pulverized and dried using high-temperature gas crushing. Ultimately, this effectively reduces the moisture content of precipitated silica products, bringing them close to or even meeting the standards for fumed silica.

[0031] 3. The present invention adopts a secondary normal pressure drying process, and the second time adopts a fluidized bed high-temperature drying method. In order to solve the agglomeration problem of powder formed by vacuuming through a twin-screw conveying method, the powder is mechanically crushed and mixed for the second time, and is impacted and sheared by fluidization. The residual moisture in the material is dried for the second time at high temperature, and the water molecules in the micropores can also be effectively evaporated at a high temperature above 800 degrees.

[0032] 4. The present invention adopts two atmospheric pressure drying processes, with the temperature of 420-450 degrees selected for the first time. The medium temperature drying is formulated based on the physical properties of alcohol and water. While ensuring the drying time, the alcohol and water contained in the surface of the silica particles and the micropores can be evaporated evenly. The medium temperature drying is to slow down the evaporation rate of the solution during the evaporation process to prevent the uneven pressure on the pore walls between pores of different sizes due to excessively high temperature and excessive evaporation, resulting in cracking and collapse. DETAILED DESCRIPTION

[0033] Example 1:

[0034] The method for producing silicon dioxide for indoor vulcanized silicone rubber comprises the following steps:

[0035] S1. Raw material preparation: Prepare a sodium silicate solution with a concentration of 1mol / L to 2mol / L: Select solid sodium silicate with a modulus of 3.0 to 3.3, dissolve it at high temperature and then precipitate it. Take the supernatant and filter it, then mix it with pure water and stir it to the corresponding molar value. The stirring speed of the stirrer is 300r / min to 500r / min, and the stirring time is 30min to 60min. When preparing a sulfuric acid solution with a concentration of 12% to 35%, mix a sulfuric acid solution with a concentration of 98% with pure water and stir it at a speed of 100r / min to 200r / min. Stirring, and then filtering through a precision ceramic filter element; preparing a surfactant mixture: the surfactant is one or a mixture of sodium lauryl sulfate, stearate and polyethylene glycol; preparing a modified silicone oil: the modifying materials are a silane coupling agent and modified silicone oil, and the modifying materials are added with an alcoholysis solution prepared by compounding an alcohol solution in advance to obtain a silane coupling agent and a modified silicone oil alcoholysis solution; the modifying material is preferably modified silicone oil polyether modified polydimethylsiloxane, the alcohol is preferably ethanol, and the mass ratio of modified silicone oil to ethanol is 1:30-50 for use in powder surface modification; anhydrous ethanol solution;

[0036] S2, 5m 3 ~8m 3 Pure water was added to the reactor and heated to 80-95°C with saturated steam. When the temperature reached 80°C, the temperature was slowly increased at a rate of 2°C / min. When the temperature reached 95°C, 1m 3 ~3m 3 The sodium silicate solution prepared in step S1 is then added with 100 kg to 300 kg of anhydrous sodium sulfate, stirred for 10 min to 15 min, and the pH value is detected to be in the range of 9 to 10.5;

[0037] S3, the sodium silicate solution prepared in step S1 is added dropwise into the reactor, and a filter is installed on the adding pipeline when the sodium silicate solution is added dropwise, and the flow rate is controlled at 8m 3 / h~12m 3 / h, the sulfuric acid solution prepared in step S1 was added dropwise into the reactor, and the flow rate was controlled at 3m 3 / h~5m 3 / h, the pH value during the reaction is controlled within the range of pH9.5 to pH10.5, the temperature is controlled within the range of 85°C to 95°C, the reaction time is 50min to 80min, and during the 50min to 80min reaction time, the reaction solution is sampled every 10min to detect the reaction progress by titration;

[0038] S4. After the reaction in step S3 is completed, stirring is carried out for 10 min to 15 min at a stirring speed of 800 rpm / min to 1000 rpm / min. Sampling ports are set at different heights and positions of the reactor so that the solution is sampled once every 5 min during the stirring time of the reactor to ensure that the materials in the reactor are evenly stirred;

[0039] S5, adding the sulfuric acid solution prepared in step S1 to the reactor three times, acidifying the material to a pH range of 4.5 to pH 5.5, then stopping the acid addition and homogenizing the solution in the reactor;

[0040] The sulfuric acid solution prepared in step S1 was added dropwise for the first time, and the flow rate was adjusted to 1m 3 / h~3m 3 / h, acidify until the pH of the material is within the range of 8.5-9.5. Stop adding acid and homogenize for 10-15 minutes;

[0041] The sulfuric acid solution prepared in step S1 was added dropwise for the second time, and the flow rate was adjusted to 1m 3 / h~3m 3 / h, acidify until the pH of the material is within the range of 7.5-8.5. Stop adding acid and homogenize for 10-15 minutes;

[0042] The sulfuric acid solution prepared in step S1 was added dropwise for the third time, and the flow rate was adjusted to 1m 3 / h~3m 3 / h, acidify until the pH of the material is within the range of 4.5 to 5.5, stop adding acid, and homogenize for 15min to 40min;

[0043] S6. After the homogenization in step S5 is completed, the material flows out of the cooling tank through the pump and is pumped into the plate and frame filter press for filtration and washing. During the filtration process, the pressure is gradually increased. The initial pressure is 0.1MPa~0.2MPa, and then pressurized to 0.3MPa~0.5MPa. When deionized water is used for washing, the temperature of the deionized water for washing is controlled at 20℃~25℃. When the conductivity of the washing water reaches <300μs / cm, the washing is stopped and extrusion is performed. After the extrusion is completed, dry compressed gas is used for air blowing for 2min~5min, and then the solvent storage tank pump is started. The material is circulated and flushed for 3min~5min using an alcohol solvent. After flushing, the alcohol solvent is collected in a dedicated storage tank. The solvent circulation flushing process in step S6 is subjected to two air blowing processes;

[0044] S7. After the solvent circulation flushing in step S6 is completed, the material obtained in step S6 is beaten, and the viscosity of the beaten slurry is controlled to be less than 550cps, and a surfactant mixture is added during the beating process, and the amount of the mixed solution added is 1% to 3% of the mass of the material; after the beating is completed, a spray drying tower is used for drying, the temperature in the drying tower is controlled at 420°C to 450°C, the outlet temperature is controlled at 105°C to 110°C, and the powder time in the tower is controlled at 10s to 20s; the conveying length of the twin-screw vacuum conveyor is 1m to 3m, and the vacuum degree is -0.4Mpa to 0.6Mpa. The dried material is collected into the intermediate silo and then conveyed to the intermediate feed hopper through the twin-screw vacuum conveyor at the lower end of the silo;

[0045] S8, the material is transported from the intermediate feed hopper to the fluidized bed for drying. The fluidized bed temperature is set at 800°C to 850°C, the drying time is controlled at 5s to 10s, and the outlet temperature is set at 105°C to 110°C;

[0046] S9. Silicone oil diluent is sprayed in the fluidized bed drying outlet pipe by spraying, and the surface of the dry powder is modified with the silicone oil diluent; the material is then transported to the air flow crusher, and the material is crushed into 6μm~8μm by high-temperature air flow to obtain condensation type room temperature vulcanized silicone rubber silica product. The gas temperature in the high-temperature air flow crusher is 180℃~220℃, the flow rate is 30m / s~50m / s, and the air flow pressure is 0.8MPa~1.2MPa.

[0047] Example 2:

[0048] The method for producing silicon dioxide for indoor vulcanized silicone rubber comprises the following steps:

[0049] S1. Raw material preparation: Prepare a sodium silicate solution with a concentration of 1mol / L to 2mol / L: Select solid sodium silicate with a modulus of 3.0 to 3.3, dissolve it at high temperature and then precipitate it. Take the supernatant and filter it, then mix it with pure water and stir it to the corresponding molar value. The stirring speed of the stirrer is 300r / min to 500r / min, and the stirring time is 30min to 60min. When preparing a sulfuric acid solution with a concentration of 12% to 35%, mix a sulfuric acid solution with a concentration of 98% with pure water and stir it at a speed of 100r / min to 200r / min. Stirring, and then filtering through a precision ceramic filter element; preparing a surfactant mixture: the surfactant is one or a mixture of sodium lauryl sulfate, stearate and polyethylene glycol; preparing a modified silicone oil: the modifying materials are a silane coupling agent and modified silicone oil, and the modifying materials are added with an alcoholysis solution prepared by compounding an alcohol solution in advance to obtain a silane coupling agent and a modified silicone oil alcoholysis solution; the modifying material is preferably modified silicone oil polyether modified polydimethylsiloxane, the alcohol is preferably ethanol, and the mass ratio of modified silicone oil to ethanol is 1:30-50 for use in powder surface modification; anhydrous ethanol solution;

[0050] S2, 5m 3 ~8m 3 Pure water was added to the reactor and heated to 80-95°C with saturated steam. When the temperature reached 80°C, the temperature was slowly increased at a rate of 2°C / min. When the temperature reached 95°C, 1m 3 ~3m 3 The sodium silicate solution prepared in step S1 is then added with 100 kg to 300 kg of anhydrous sodium sulfate, stirred for 10 min to 15 min, and the pH value is detected to be in the range of 9 to 10.5;

[0051] S3, the sodium silicate solution prepared in step S1 is added dropwise into the reactor, and a filter is installed on the adding pipeline when the sodium silicate solution is added dropwise, and the flow rate is controlled at 8m 3 / h~12m 3 / h, the sulfuric acid solution prepared in step S1 was added dropwise into the reactor, and the flow rate was controlled at 3m 3 / h~5m 3 / h, the pH value during the reaction is controlled within the range of pH9.5 to pH10.5, the temperature is controlled within the range of 85°C to 95°C, the reaction time is 50min to 80min, and during the 50min to 80min reaction time, the reaction solution is sampled every 10min to detect the reaction progress by titration;

[0052] S4. After the reaction in step S3 is completed, stirring is carried out for 10 min to 15 min at a stirring speed of 800 rpm / min to 1000 rpm / min. Sampling ports are set at different heights and positions of the reactor so that the solution is sampled once every 5 min during the stirring time of the reactor to ensure that the materials in the reactor are evenly stirred;

[0053] S5, adding the sulfuric acid solution prepared in step S1 to the reactor three times, acidifying the material to a pH range of 4.5 to pH 5.5, then stopping the acid addition and homogenizing the solution in the reactor;

[0054] The sulfuric acid solution prepared in step S1 was added dropwise for the first time, and the flow rate was adjusted to 1m 3 / h~3m 3 / h, acidify until the pH of the material is within the range of 8.5-9.5. Stop adding acid and homogenize for 10-15 minutes;

[0055] The sulfuric acid solution prepared in step S1 was added dropwise for the second time, and the flow rate was adjusted to 1m 3 / h~3m 3 / h, acidify until the pH of the material is within the range of 7.5-8.5. Stop adding acid and homogenize for 10-15 minutes;

[0056] The sulfuric acid solution prepared in step S1 was added dropwise for the third time, and the flow rate was adjusted to 1m 3 / h~3m 3 / h, acidify until the pH of the material is within the range of 4.5 to 5.5, stop adding acid, and homogenize for 15min to 40min;

[0057] S6. After the homogenization in step S5 is completed, the material flows out of the cooling tank through the pump and is pumped into the plate and frame filter press for filtration and washing. During the filtration process, the pressure is gradually increased. The initial pressure is 0.1MPa-0.2MPa, and then the pressure is increased to 0.3MPa-0.5MPa. When deionized water is used for washing, the temperature of the deionized water for washing is controlled at 20°C-25°C. When the conductivity of the washing water reaches <300μs / cm, the washing is stopped and extrusion is performed. After the extrusion is completed, dry compressed gas is used for air blowing for 2min-5min;

[0058] S7. After the solvent circulation flushing in step S6 is completed, the material obtained in step S6 is beaten, and the viscosity of the beaten slurry is controlled to be less than 550cps, and a surfactant mixture is added during the beating process, and the amount of the mixed solution added is 1% to 3% of the mass of the material; after the beating is completed, a spray drying tower is used for drying, the temperature in the drying tower is controlled at 420°C to 450°C, the outlet temperature is controlled at 105°C to 110°C, and the powder time in the tower is controlled at 10s to 20s; the conveying length of the twin-screw vacuum conveyor is 1m to 3m, and the vacuum degree is -0.4Mpa to 0.6Mpa. The dried material is collected into the intermediate silo and then conveyed to the intermediate feed hopper through the twin-screw vacuum conveyor at the lower end of the silo;

[0059] S8, the material is transported from the intermediate feed hopper to the fluidized bed for drying. The fluidized bed temperature is set at 800°C to 850°C, the drying time is controlled at 5s to 10s, and the outlet temperature is set at 105°C to 110°C;

[0060] S9. Silicone oil diluent is sprayed in the fluidized bed drying outlet pipe by spraying, and the surface of the dry powder is modified with the silicone oil diluent; the material is then transported to the air flow crusher, and the material is crushed into 6μm~8μm by high-temperature air flow to obtain condensation type room temperature vulcanized silicone rubber silica product. The gas temperature in the high-temperature air flow crusher is 180℃~220℃, the flow rate is 30m / s~50m / s, and the air flow pressure is 0.8MPa~1.2MPa.

[0061] Example 3:

[0062] S1. Raw material preparation: Prepare a sodium silicate solution with a concentration of 1mol / L to 2mol / L: Select solid sodium silicate with a modulus of 3.0 to 3.3, dissolve it at high temperature and then precipitate it. Take the supernatant and filter it, then mix it with pure water and stir it to the corresponding molar value. The stirring speed of the stirrer is 300r / min to 500r / min, and the stirring time is 30min to 60min. When preparing a sulfuric acid solution with a concentration of 12% to 35%, mix a sulfuric acid solution with a concentration of 98% with pure water and stir it at a speed of 100r / min to 200r / min. Stirring, and then filtering through a precision ceramic filter element; preparing a surfactant mixture: the surfactant is one or a mixture of sodium lauryl sulfate, stearate and polyethylene glycol; preparing a modified silicone oil: the modifying materials are a silane coupling agent and modified silicone oil, and the modifying materials are added with an alcoholysis solution prepared by compounding an alcohol solution in advance to obtain a silane coupling agent and a modified silicone oil alcoholysis solution; the modifying material is preferably modified silicone oil polyether modified polydimethylsiloxane, the alcohol is preferably ethanol, and the mass ratio of modified silicone oil to ethanol is 1:30-50 for use in powder surface modification; anhydrous ethanol solution;

[0063] S2, 5m3 ~8m 3 Pure water was added to the reactor and heated to 80-95°C with saturated steam. When the temperature reached 80°C, the temperature was slowly increased at a rate of 2°C / min. When the temperature reached 95°C, 1m 3 ~3m 3 The sodium silicate solution prepared in step S1 is then added with 100 kg to 300 kg of anhydrous sodium sulfate, stirred for 10 min to 15 min, and the pH value is detected to be in the range of 9 to 10.5;

[0064] S3, the sodium silicate solution prepared in step S1 is added dropwise into the reactor, and a filter is installed on the adding pipeline when the sodium silicate solution is added dropwise, and the flow rate is controlled at 8m 3 / h~12m 3 / h, the sulfuric acid solution prepared in step S1 was added dropwise into the reactor, and the flow rate was controlled at 3m 3 / h~5m 3 / h, the pH value during the reaction is controlled within the range of pH9.5 to pH10.5, the temperature is controlled within the range of 85°C to 95°C, the reaction time is 50min to 80min, and during the 50min to 80min reaction time, the reaction solution is sampled every 10min to detect the reaction progress by titration;

[0065] S4. After the reaction in step S3 is completed, stirring is carried out for 10 min to 15 min at a stirring speed of 800 rpm / min to 1000 rpm / min. Sampling ports are set at different heights and positions of the reactor so that the solution is sampled once every 5 min during the stirring time of the reactor to ensure that the materials in the reactor are evenly stirred;

[0066] S5, adding the sulfuric acid solution prepared in step S1 to the reactor three times, acidifying the material to a pH range of 4.5 to pH 5.5, then stopping the acid addition and homogenizing the solution in the reactor;

[0067] The sulfuric acid solution prepared in step S1 was added dropwise for the first time, and the flow rate was adjusted to 1m 3 / h~3m 3 / h, acidify until the pH of the material is within the range of 8.5-9.5. Stop adding acid and homogenize for 10-15 minutes;

[0068] The sulfuric acid solution prepared in step S1 was added dropwise for the second time, and the flow rate was adjusted to 1m 3 / h~3m 3 / h, acidify until the pH of the material is within the range of 7.5-8.5. Stop adding acid and homogenize for 10-15 minutes;

[0069] The sulfuric acid solution prepared in step S1 was added dropwise for the third time, and the flow rate was adjusted to 1m 3 / h~3m 3 / h, acidify until the pH of the material is within the range of 4.5 to 5.5, stop adding acid, and homogenize for 15min to 40min;

[0070] S6. After the homogenization in step S5 is completed, the material flows out of the cooling tank through the pump and is pumped into the plate and frame filter press for filtration and washing. During the filtration process, the pressure is gradually increased. The initial pressure is 0.1MPa-0.2MPa, and then the pressure is increased to 0.3MPa-0.5MPa. When deionized water is used for washing, the temperature of the deionized water for washing is controlled at 20°C-25°C. When the conductivity of the washing water reaches <300μs / cm, the washing is stopped and extrusion is performed. After the extrusion is completed, dry compressed gas is used for air blowing for 2min-5min;

[0071] S7. After the solvent circulation flushing in step S6 is completed, the material obtained in step S6 is beaten, and the viscosity of the beaten slurry is controlled to be less than 550cps, and a surfactant mixture is added during the beating process, and the amount of the mixed solution added is 1% to 3% of the mass of the material; after the beating is completed, a spray drying tower is used for drying, the temperature in the drying tower is controlled at 650°C to 750°C, the outlet temperature is controlled at 105°C to 110°C, and the powder time in the tower is controlled at 10s to 20s; the conveying length of the twin-screw vacuum conveyor is 1m to 3m, and the vacuum degree is -0.4Mpa to 0.6Mpa. The dried material is collected into the intermediate silo and then conveyed to the intermediate feed hopper through the twin-screw vacuum conveyor at the lower end of the silo;

[0072] S8, the material is transported from the intermediate feed hopper to the fluidized bed for drying. The fluidized bed temperature is set at 85℃~95℃, the drying time is controlled at 5s~10s, and the outlet temperature is set at 65℃~75℃;

[0073] S9. Silicone oil diluent is sprayed in the fluidized bed drying outlet pipe by spraying, and the surface of the dry powder is modified with the silicone oil diluent; the material is then transported to the air flow crusher, and the material is crushed into 6μm~8μm by high-temperature air flow to obtain condensation type room temperature vulcanized silicone rubber silica product. The gas temperature in the high-temperature air flow crusher is 180℃~220℃, the flow rate is 30m / s~50m / s, and the air flow pressure is 0.8MPa~1.2MPa.

[0074] Example 2 eliminated the process of replacing water with alcohol;

[0075] In Example 3, the process of replacing water with alcohol and the second drying were eliminated, and the temperature of the fluidized bed was reduced to 85°C to 95°C.

[0076] As can be seen from the following table, Example 1 is the optimal Example 1; compared with Example 1, Example 2 cancels the replacement process of alcohol and water. Although the secondary drying process is adopted, the water content is still high; compared with Example 1, Example 3 cancels the replacement process of alcohol and water and also cancels the secondary drying process. The water content is obviously the highest, indicating that the moisture cannot be effectively reduced by the normal pressure drying method; through the above experiments, it is effectively demonstrated that the replacement process of alcohol and water in the present technical process effectively reduces the water molecules contained in the micropores and surfaces of the particles, and then through the three drying methods of medium temperature, high temperature and low temperature combined with time control, the integrity of the pores is maintained while the moisture content is effectively removed.

[0077] Table 1 is a comparison of the test data of the silica particles of Examples 1 to 3.

[0078]

[0079]

[0080] The above shows and describes the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are merely preferred examples of the present invention and are not intended to limit the present invention. Various changes and improvements may be made to the present invention without departing from the spirit and scope of the present invention. Such changes and improvements fall within the scope of the present invention. The scope of protection claimed in the present invention is defined by the appended claims and their equivalents.

Claims

1. Indoor production method of silicon dioxide for vulcanized silicone rubber, characterized by: The following steps are involved: S1. Raw material preparation: prepare sodium silicate solution with a concentration of 1mol / L to 2mol / L; prepare sulfuric acid solution with a concentration of 12% to 35%; prepare surfactant mixture; prepare modified silicone oil; Anhydrous ethanol solution; S2, 5m 3 ~8m 3 Pure water was added to the reactor and heated to 80℃~95℃ with saturated steam. Then 1m 3 ~3m 3 The sodium silicate solution prepared in step S1 is then added with 100 kg to 300 kg of anhydrous sodium sulfate, stirred for 10 min to 15 min, and the pH value is detected to be in the range of 9 to 10.5; S3, the sodium silicate solution prepared in step S1 is added dropwise into the reactor at a flow rate of 8m 3 / h~12m 3 / h, the sulfuric acid solution prepared in step S1 was added dropwise into the reactor, and the flow rate was controlled at 3m 3 / h~5m 3 / h, the pH value during the reaction is controlled within the range of pH9.5 to pH10.5, the temperature is controlled within the range of 85°C to 95°C, and the reaction time is 50min to 80min; S4. After the reaction in step S3 is completed, stirring for 10 min to 15 min at a stirring speed of 800 rpm / min to 1000 rpm / min; S5, adding the sulfuric acid solution prepared in step S1 to the reactor three times, acidifying the material to a pH range of 4.5 to pH 5.5, then stopping the acid addition and homogenizing the solution in the reactor; S6. After the homogenization in step S5 is completed, the material flows out of the cooling tank through the pump and is pumped into the plate and frame filter press for filtration and washing. When the conductivity of the washing water reaches <300 μs / cm, the washing is stopped and extrusion is performed. After the extrusion is completed, dry compressed gas is used for air blowing for 2 min to 5 min, and then the solvent storage tank pump is started. The material is circulated and flushed with an alcohol solvent for 3 min to 5 min. After flushing, the alcohol solvent is collected in a dedicated storage tank. The solvent circulation flushing process in step S6 is subjected to two air blowing processes; S7. After the solvent circulation flushing in step S6 is completed, the material obtained in step S6 is beaten, and a surfactant mixture is added during the beating process, with the amount of the mixture added being 1% to 3% of the mass of the material; after the beating is completed, the material is dried using a spray drying tower, and the dried material is collected into an intermediate silo and then conveyed to the intermediate feed hopper by a twin-screw vacuum conveyor at the lower end of the silo; S8, the material is transported from the intermediate feed hopper to the fluidized bed for drying. The fluidized bed temperature is set at 800°C to 850°C, the drying time is controlled at 5s to 10s, and the outlet temperature is set at 105°C to 110°C; S9. The outlet pipe of the fluidized bed dryer is sprayed with silicone oil diluent by spraying, and the surface of the dry powder is modified with the silicone oil diluent; the material is then transported to the air flow crusher, and the high-temperature air flow is used to crush the material to 6μm to 8μm, thereby obtaining a condensation-type room temperature vulcanized silicone rubber silica product.

2. The method for producing silica for indoor vulcanized silicone rubber according to claim 1, wherein: In the step S1, when preparing a sodium silicate solution with a concentration of 1 to 2 mol / L, solid sodium silicate with a modulus of 3.0 to 3.3 is selected, dissolved at high temperature and then precipitated, the supernatant is filtered and mixed with pure water, the stirring speed of the stirrer is 300 r / min to 500 r / min, the stirring time is 30 min to 60 min, and the liquid is adjusted to the corresponding molarity; when preparing a sulfuric acid solution with a concentration of 12% to 35%, a sulfuric acid solution with a concentration of 98% is mixed with pure water, and the stirring speed is 100 r / min to 20 0r / min, and then filtered through a precision ceramic filter element; surfactant, the surfactant is one of sodium lauryl sulfate, stearate and polyethylene glycol or a mixture; modified silicone oil, the modified material is a silane coupling agent and modified silicone oil, the modified material is added with an alcoholysis solution prepared by compounding an alcohol solution in advance to obtain a silane coupling agent and a modified silicone oil alcoholysis solution; the modified material is preferably modified silicone oil polyether modified polydimethylsiloxane, the alcohol is preferably ethanol, and the mass ratio of modified silicone oil: ethanol is 1:30-50 for use as powder surface modification.

3. The method for producing silica for indoor vulcanized silicone rubber according to claim 1, wherein: In step S2, when the temperature reaches 80°C, the temperature is slowly increased at a rate of 2°C / min to 95°C.

4. The method for producing silica for indoor vulcanized silicone rubber according to claim 1, wherein: In step S3, when the sodium silicate solution is added dropwise, a filter is installed on the dropping pipeline; during the reaction period of 50 to 80 minutes, the reaction solution is sampled every 10 minutes, and the reaction progress is detected by titration.

5. The method for producing silica for indoor vulcanized silicone rubber according to claim 1, wherein: In step S4, by setting sampling ports at different heights and positions of the reactor, the reaction solution is sampled once every 5 minutes during the stirring time of the reactor to ensure that the materials in the reactor are stirred evenly.

6. The method for producing silica for indoor vulcanized silicone rubber according to claim 1, wherein: In step S5, the sulfuric acid solution prepared in step S1 is added dropwise for the first time, and the flow rate is adjusted to 1m 3 / h~3m 3 / h, acidify until the pH of the material is within the range of 8.5-9.

5. Stop adding acid and homogenize for 10-15 minutes; The sulfuric acid solution prepared in step S1 was added dropwise for the second time, and the flow rate was adjusted to 1m 3 / h~3m 3 / h, acidify until the pH of the material is within the range of 7.5-8.

5. Stop adding acid and homogenize for 10-15 minutes; The sulfuric acid solution prepared in step S1 was added dropwise for the third time, and the flow rate was adjusted to 1m 3 / h~3m 3 / h, acidify to the pH range of 4.5 to pH 5.5, stop adding acid, and homogenize for 15min to 40min.

7. The method for producing silica for indoor vulcanized silicone rubber according to claim 1, wherein: In step S6, during the filter pressing process, the pressure is gradually increased, with the initial pressure being 0.1 MPa to 0.2 MPa and then being pressurized to 0.3 MPa to 0.5 MPa; when deionized water is used for washing, the temperature of the deionized water for washing is controlled at 20° C. to 25° C.

8. The method for producing silica for indoor vulcanized silicone rubber according to claim 1, wherein: In step S7, the viscosity of the slurry is controlled at <550cps; the temperature in the drying tower is controlled at 420°C to 450°C, the outlet temperature is controlled at 105°C to 110°C, and the time the powder stays in the tower is controlled at 10s to 20s; the conveying length of the twin-screw vacuum conveyor is 1m to 3m, and the vacuum degree is -0.4Mpa to 0.6Mpa.

9. The method for producing silica for indoor vulcanized silicone rubber according to claim 1, wherein: In step S9, the gas temperature in the high-temperature air flow crusher is 180° C. to 220° C., the flow rate is 30 m / s to 50 m / s, and the pressure of the air flow is 0.8 MPa to 1.2 MPa.

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