Spherical silicon dioxide particles as well as preparation method and application thereof

Abstract

The invention relates to the technical field of fillers, and discloses spherical silicon dioxide particles as well as a preparation method and application thereof. According to the preparation method, polysiloxane particles are taken as raw materials for calcining condition adjustment, specifically, step-by-step heat treatment and adjustment of temperature, atmosphere and heat treatment time in each step are carried out, so that the pore structure of the product particles is controlled, the spherical silicon dioxide particles with large pores are prepared, and particularly, the spherical silicon dioxide particles with large pores are prepared. According to the present invention, the silica particles with the particle size of less than 100 nm can have large pores, and the diameter of the pores can achieve more than 0.5 nm so as to obtain the spherical silica particles with the high water absorption.

Description

Technical Field

[0001] The present invention relates to the technical field of nano-fillers, and particularly to a spherical silica particle, a preparation method thereof, and an application thereof. Background Art

[0002] Toner is commonly used in digital copiers and laser printers to achieve electrostatic development. In a high-humidity environment, since toner easily absorbs moisture in the environment, the chargeability of the toner deviates, resulting in image defects. To prevent the chargeability of the toner from deviating, a hydrophobic modification material is usually added to the toner to prevent the toner from absorbing moisture in the environment.

[0003] Using hydrophobic silica with a large specific surface area as an externally added particle in toner can effectively prevent the toner from absorbing moisture in the environment, thereby maintaining the stability of its chargeability. The silica provided in the prior art has poor adsorption performance and low water adsorption capacity due to its low porosity and small specific surface area. After surface hydrophobization treatment of silica with low porosity and low water adsorption capacity and using it as an externally added particle of toner, the ability to balance the chargeability stability of the toner is poor.

[0004] The preparation method of silica in the prior art is as shown in the Chinese patent with the application publication number CN101962192A, which discloses a preparation method of a highly adsorptive porous silica adsorbent. Specifically, by dissolving polyvinylpyrrolidone in water and then adding an acid, a water / acid / polyvinylpyrrolidone solution is obtained; then a silanolate is added to obtain a sol, which is then gelled, dried, and calcined to obtain a highly adsorptive porous silica adsorbent. In this patent, the sol-gel method is used to prepare silica particles, and the obtained silica particles have small pores and low porosity, so the water absorption performance is low, and the amount of water that can be adsorbed in the particles is low. Summary of the Invention

[0005] To solve the above technical problem of low water adsorption capacity of silica, the present invention provides a spherical silica particle with high water absorption, a preparation method thereof, and an application thereof.

[0006] The specific technical solution of the present invention is as follows: In a first aspect, the present invention provides a preparation method of a spherical silica particle with high water absorption, including the following steps: Step S1: Under an inert gas atmosphere, heat-treat the polysiloxane particles to form a carbon-containing silica particle matrix with a carbon content of 8.3-16.5 wt%. Step S2: Under an air atmosphere, heat-treat the carbon-containing silica particle matrix at a temperature of 400-800 °C to obtain porous silica particles.

[0007] In the prior art, the pores of silica particles are small and the porosity is low, resulting in poor water absorption and a small amount of adsorbed water.

[0008] Generally speaking, the larger the specific surface area of powder particles, the stronger the adsorption performance. However, the inventor found in the experiment that the amount of water that can be adsorbed in silica particles has a great relationship with the size of the pores. If the pores in the silica particles are small, even if the number of pores in the particles is increased to improve the porosity and specific surface area, or the particle size is small and the number of pores is large to improve the porosity and specific surface area, the amount of adsorbed water in the silica particles cannot be increased.

[0009] The inventor further found that after the particles adsorb water, the water cannot enter the interior of the particles and adhere to the particle surface. A large number of water molecules stay on the particle surface, resulting in further adsorption of water molecules. Therefore, the water absorption of silica particles with small pores is low.

[0010] In order to prepare spherical silica particles with high water absorption, the present invention is finally realized by preparing spherical silica particles with a small particle size and large pore diameter. More specifically, the present invention is realized through a step-by-step heat treatment process: the first heat treatment is heat treatment in an inert gas atmosphere using polysiloxane particles as raw materials, and the control of the carbon content in the particles during this heat treatment process, so that an appropriate amount of carbon occupies the pores in the particles first; after the first heat treatment, the second heat treatment at 400-800 °C in an air atmosphere removes the carbon to finally control the pore structure of the product particles, and spherical silica particles with moderate pores are prepared. At the same time, by the method provided by the present invention, even silica particles with a particle size less than 300 nm can have relatively large pores, and the diameter of the pores can reach more than 0.5 nm.

[0011] In the preparation method provided by the present invention, the preparation of a porous structure in silicon dioxide particles is achieved through two-step heat treatment. First, a heat treatment step in an inert gas atmosphere is carried out. This step promotes the direct carbonization of alkyl groups in polysiloxane and retains carbon in the particle structure. Then, a heat treatment step in an air atmosphere is carried out. This step is heat-treated at 400 - 800 °C, which promotes the gasification of the carbon retained in the particle structure and ensures that the positions occupied by carbon in the particle structure will not be occupied by silicon dioxide, thereby ensuring the existence of pores in the particle structure, and the pore diameter can reach more than 0.5 nm. In the heat treatment step in an air atmosphere, the temperature cannot be higher than 800 °C. Since the reaction between oxygen and carbon generates certain heat, this heat will cause the temperature in the particle structure to reach the temperature required for the melting of silicon dioxide during heat treatment, thereby causing the molten silicon dioxide to fill the positions originally occupied by carbon in the particle structure, resulting in smaller pores or even densification in the product particles. In the heat treatment step in an air atmosphere, the temperature cannot be lower than 400 °C. Otherwise, the air cannot completely remove the carbon in the particle structure, and the pores in the particles are small and few.

[0012] In order to form larger pores in the silicon dioxide particles, the carbon content of the carbon-containing silicon dioxide particle matrix needs to be 8.3 wt% - 16.5 wt%. Since the reaction between carbon and air is an exothermic reaction, heat will be generated during the process of removing carbon in the second-step heat treatment. Excessive heat will cause the temperature of the silicon dioxide particles to be relatively high and cause partial melting of the silicon dioxide. The molten silicon dioxide liquid will fill the pores in the particles. Therefore, in order to form larger pores in the silicon dioxide particles in the preparation method of the present invention, the carbon content of the carbon-containing silicon dioxide particle matrix needs to be strictly controlled.

[0013] In the carbon-containing silicon dioxide particle matrix obtained by the heat treatment step in an inert gas atmosphere, the carbon content cannot exceed 16.5 wt%. Otherwise, there will be a problem that the silicon dioxide around the pores will be melted during the heat treatment step in an air atmosphere, and then a problem that the molten silicon dioxide fills the pores and densifies the particle product will occur. The reason is that when too much carbon reacts with oxygen to form carbon dioxide, more heat will be generated. Therefore, this heat causes the temperature in the particle structure to far exceed 800 °C, and then causes the silicon dioxide in the particle structure to be melted. Especially for small-sized particles, the heat generated when these carbons react to form carbon dioxide will directly cause the particles to be densified, with extremely few pores in the particle structure and extremely small pore diameters.

[0014] In the carbon-containing silicon dioxide particle matrix obtained by the heat treatment step in an inert gas atmosphere, the carbon content cannot be less than 8.3 wt%. Otherwise, there will be fewer vacancies formed in the particles after the carbon is removed during the heat treatment step in an air atmosphere, and finally, there will be fewer pores and smaller pore diameters in the particle structure.

[0015] Preferably, the carbon content of the carbon-containing silica particle matrix is 10-13 wt%.

[0016] When the carbon content of the carbon-containing silica particle matrix is 10-13 wt%, even silica particles with a particle size less than 100 nm can have relatively large pores, and the diameter of the pores can reach the range of 0.5-2 nm.

[0017] Preferably, the average particle size of the porous silica particles is 50-300 nm.

[0018] The smaller the particle size of the porous silica particles, the larger and more pores there are in the particles, and the larger the specific surface area of the particles. For silica particles with an average particle size of 50-300 nm, due to the small particle size, when preparing larger pores in the particles, it will cause particle fragmentation. There is no effective method for pore regulation of small-particle-size silica particles in the prior art. Through the above preparation method of the present invention, larger and more pores can be prepared and retained in silica particles with an average particle size of 50-300 nm. And due to the small particle size of the particles, the specific surface area of the prepared silica particles with an average particle size of 50-300 nm is significantly increased, showing great advantages in enhancing the adsorption performance of the particles. This advantage stems from the fact that the method of the present invention can enable larger pores to exist in small-particle-size silica particles.

[0019] [[ID=A12]]More preferably, the average particle size of the porous silica particles is 50-100 nm.

[0020] Preferably, the heat treatment temperature in step S1 is 650-1200 °C, and the heat treatment time is 3-20 hours.

[0021] In the heat treatment step under an inert gas atmosphere, the temperature should not be higher than 1200 °C. If the temperature is too high, water molecules in the particles will directly carry away alkyl carbon, resulting in dense spherical particles obtained in step S1. And the temperature of this step should not be lower than 650 °C. At the same time, the time of this step should not be shorter than 3 hours. If the temperature is too low or the heat treatment time is less than 3 hours, the alkyl groups in the particles will not be completely carbonized. These incompletely carbonized alkyl groups will cause the collapse of the pores in the particles in the next carbonization step, reducing the space for water molecules to attach in the product particles and resulting in a low water absorption capacity of the product particles.

[0022] Preferably, the heat treatment time in step S² is 7-32 hours.

[0023] Preferably, the temperature difference between the treatments in step S1 and step S2 is 300-600 °C

[0024] An appropriate temperature difference can reduce the generation of molten silica in the heat treatment step of the air atmosphere and avoid the filling of pores with molten silica liquid.

[0025] As a preference of the above preparation method, the heat treatment in step S2 is divided into the following two stages: The first stage: oxidize the residual organic matter at 400 - 500 °C, and keep the temperature for 2 - 8 hours; The second stage: stabilize the pore structure at 600 - 800 °C, and keep the temperature for 5 - 24 hours.

[0026] As a preference of the above preparation method, the following steps are further included: surface-treat the porous silica particles with hexamethyldisilazane.

[0027] More preferably, the surface treatment method is: add hexamethyldisilazane to the porous silica particles, knead, and dry.

[0028] The treatment with hexamethyldisilazane can increase the hydrophobicity of the surface of the porous silica particles, make the surface hydrophobic, and can better increase the dispersibility and fluidity of the toner.

[0029] In the second aspect, the present invention provides a spherical silica particle. The average particle size of the spherical silica particle is 50 - 300 nm, and the pore diameter of the spherical silica particle is 0.5 - 2 nm.

[0030] As a preference of the above spherical silica particle, the average particle size of the spherical silica particle is 50 - 100 nm.

[0031] In the third aspect, the present invention provides an application of a spherical silica particle as an external additive particle for toner.

[0032] If a silica sphere with a high water absorption amount is added to the toner, the silica sphere with a high water absorption amount can adsorb water molecules under high humidity conditions, prevent the charge amount of the toner from decreasing, ensure the charging stability of the toner, and at the same time, the addition of the silica sphere can increase the dispersibility and fluidity of the toner.

[0033] In the fourth aspect, the present invention provides an application of a spherical silica particle as an additive for matrix powder. Using the above spherical silica particle as an additive for matrix powder can improve the dispersibility and fluidity of the matrix powder. For example, as an additive for toner, it can improve the dispersibility and fluidity of the toner.

[0034] Compared with the prior art, the present invention has the following technical effects: The present invention is finally realized by preparing spherical silica particles with small particle size and large pore diameter. More specifically, the present invention is realized through a step-by-step heat treatment process: the first heat treatment is heat treatment in an inert gas atmosphere with polysiloxane particles as raw materials, and the control of the carbon content in the particles during this heat treatment process, so that an appropriate amount of carbon occupies the pores in the particles first; after the first heat treatment, the second heat treatment at 400-800°C in an air atmosphere removes the carbon to finally control the pore structure of the product particles, and spherical silica particles with moderate pores are prepared. At the same time, by the method provided by the present invention, even silica particles with a particle size less than 300 nm can have relatively large pores, and the diameter of the pores can reach more than 0.5 nm.

[0035] In particular, the preparation method of the present invention can enable even silica particles with a particle size less than 100 nm to have relatively large pores, the diameter of the pores can reach more than 0.5 nm, and even more than 1.0 nm, and finally provide silica particles with a high water absorption capacity, and the water absorption capacity reaches more than 1.67%. Detailed implementation mode

[0036] The present invention will be further described below in conjunction with embodiments. Those of ordinary skill in the art will be able to implement the present invention based on these descriptions. In addition, the embodiments of the present invention involved in the following descriptions are usually only a part of the embodiments of the present invention, rather than all the embodiments. Therefore, all other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention.

[0037] In one embodiment, the present invention provides a method for preparing spherical silica particles with high water absorption capacity, including the following steps: Step S1: Heat-treat the polysiloxane particles in an inert gas atmosphere to form a carbon-containing silica particle matrix with a carbon content of 8.3-16.5 wt%. Step S2: Heat-treat the carbon-containing silica particle matrix at a temperature of 400-800°C in an air atmosphere to obtain porous silica particles.

[0038] In the prior art, the pores of silica particles are small and the porosity is low, resulting in poor water absorption and small water absorption capacity.

[0039] In the experiments, the present inventor found that the amount of water that can be adsorbed in silica particles has a great relationship with the pore size. If the pores in the silica particles are small, even if the number of pores in the particles is increased to improve the porosity and specific surface area, or the particle size is small and the number of pores is large to improve the porosity and specific surface area, the amount of adsorbed water in the silica particles cannot be increased.

[0040] The inventor further studied and found that after the particles adsorb water, the water cannot enter the interior of the particles and attach to the particle surface. A large number of water molecules stay on the particle surface, resulting in further adsorption of water molecules. Therefore, the water absorption capacity of silica particles with small pores is low.

[0041] In order to prepare spherical silica particles with a high water absorption capacity, this embodiment is finally realized by preparing spherical silica particles with a small particle size and large pore diameter. More specifically, it is realized through a step-by-step heat treatment process: the first heat treatment is heat treatment in an inert gas atmosphere with polysiloxane particles as raw materials, and the control of the carbon content in the particles during this heat treatment process, so that an appropriate amount of carbon occupies the pores in the particles first; after the first heat treatment, the second heat treatment at 400-800°C in an air atmosphere removes the carbon to finally control the pore structure of the product particles, and spherical silica particles with moderate pores are prepared. At the same time, by the method provided by the present invention, even silica particles with a particle size less than 300 nm can have relatively large pores, and the diameter of the pores can reach more than 0.5 nm.

[0042] In the preparation method provided in the above embodiment, the porous structure in the silica particles is prepared through two-step heat treatment. First, a heat treatment step in an inert gas atmosphere is carried out. This step of heat treatment promotes the direct carbonization of the alkyl groups in the polysiloxane and keeps the carbon in the particle structure. Then, a heat treatment step in an air atmosphere is carried out. This step is heat-treated at 400-800°C to promote the gasification of the carbon retained in the particle structure and ensure that the positions occupied by carbon in the particle structure will not be occupied by silica, thereby ensuring the existence of pores in the particle structure, and the pore diameter can reach more than 0.5 nm.

[0043] For the heat treatment step in an air atmosphere, the temperature cannot be higher than 800°C. Since the reaction between oxygen and carbon will generate a certain amount of heat, this heat will cause the temperature required for silica melting in the particle structure during heat treatment, and then cause the molten silica to fill the positions originally occupied by carbon in the particle structure, resulting in smaller pores or even densification in the product particles. And when the temperature is greater than 800°C, under the combined action of moisture and oxygen, the carbon is quickly removed from the particles, generating a large amount of heat, and the particles are severely densified. Once the temperature is too high, it is difficult to maintain the existence of the pore structure in the particles.

[0044] The heat treatment step in an air atmosphere, the temperature should not be lower than 400 °C, otherwise, the air cannot completely remove the carbon in the particle structure, and the pores in the particles are small and few.

[0045] In one embodiment, the carbon content of the carbon-containing silica particle matrix is 8.3 wt% to 16.5 wt%, which can form larger pores in the silica particles.

[0046] Since the reaction of carbon with air is an exothermic reaction, heat will be generated during the process of removing carbon in the second heat treatment. Excessive heat will cause the temperature of the silica particles to be relatively high, resulting in partial melting of the silica. And the molten silica liquid will fill the pores in the particles. Therefore, in order to form larger pores in the silica particles, it is necessary to strictly control the carbon content of the carbon-containing silica particle matrix.

[0047] When carrying out the method of the present invention, in the carbon-containing silica particle matrix obtained by the heat treatment step in an inert gas atmosphere, the carbon content should not exceed 16.5 wt%, otherwise it will lead to the problem that the silica around the pores is melted in the heat treatment step in an air atmosphere, and further lead to the problem that the molten silica fills the pores to densify the particle product. The reason is that when excessive carbon reacts with oxygen to form carbon dioxide, more heat will be generated. Therefore, these heats cause the temperature in the particle structure to far exceed 800 °C, and then lead to the melting of silica in the particle structure. Especially for small-sized particles, the heat generated when these carbons react to form carbon dioxide will directly cause the particles to densify, with extremely few pores in the particle structure and extremely small pore diameters.

[0048] When carrying out the method of the present invention, in the carbon-containing silica particle matrix obtained by the heat treatment step in an inert gas atmosphere, the carbon content should not be less than 8.3 wt%, otherwise it will lead to fewer vacancies formed in the particles after the carbon is removed in the heat treatment step in an air atmosphere, and ultimately lead to fewer pores and smaller pore diameters in the particle structure.

[0049] In a preferred embodiment, the carbon content of the carbon-containing silica particle matrix is 10-13 wt%.

[0050] 8]When the carbon content of the carbon-containing silica particle matrix is 10-13 wt%, it can be ensured that even silica particles with a particle size less than 100 nm can have larger pores, and the diameter of the pores can reach the range of 0.5-2 nm.

[0051] In one embodiment, the average particle size of the porous silica particles is 50-300 nm.

[0052] The smaller the particle size of the porous silica particles, the larger and more numerous the pores in the particles, and the larger the specific surface area of the particles. For silica particles with an average particle size of 50 - 300 nm, due to the small particle size, when preparing larger pores in the particles, it will cause particle fragmentation, and there is no effective method for pore regulation of small particle size silica particles in the prior art. Through the preparation method of this embodiment, larger and more numerous pores can be prepared in silica particles with an average particle size of 50 - 300 nm, and due to the small particle size of the particles, the specific surface area of the prepared silica particles with an average particle size of 50 - 300 nm is significantly increased, showing great advantages in enhancing the adsorption performance of the particles. And this advantage stems from the fact that the method of the present invention can make the small particle size silica particles also have larger pores.

[0053] In a preferred embodiment, the average particle size of the porous silica particles is 50 - 100 nm.

[0054] In a preferred embodiment, the heat treatment temperature in step S1 is 650 - 1200 °C, and the heat treatment time is 3 - 20 hours.

[0055] For the heat treatment step in an inert gas atmosphere, the temperature cannot be higher than 1200 °C. If the temperature is too high, it will cause the water molecule gas in the particles to directly carry away the alkyl carbon, resulting in the formation of dense spherical particles in step S1; and the temperature of this step cannot be lower than 650 °C. At the same time, the time of this step cannot be shorter than 3 hours. If the temperature is too low or the heat treatment time is less than 3 hours, it will cause incomplete alkyl carbonization in the particles. These incompletely carbonized alkyls will cause the collapse of the pores in the particles in the next carbonization step, reducing the space for water molecules to attach in the product particles and resulting in a low water absorption capacity of the product particles.

[0056] In a preferred embodiment, the heat treatment time in step S2 is 7 - 32 hours.

[0057] In a preferred embodiment, the temperature difference between the treatments of step S1 and step S2 is 300 - 600 °C.

[0058] An appropriate temperature difference can reduce the generation of molten silica in the heat treatment step in an air atmosphere and avoid the filling of pores by the molten silica solution.

[0059] In a preferred embodiment, the heat treatment of step S2 is divided into the following two stages: The first stage: Oxidize the residual organic matter at 400 - 500 °C, with a holding time of 2 - 8 hours; The second stage: Stabilize the pore structure at 600 - 800 °C, with a holding time of 5 - 24 hours.

[0060] In a preferred embodiment, the following step is further included: surface-treat the porous silica particles with hexamethyldisilazane.

[0061] Further preferably, the surface treatment method is: adding hexamethyldisilazane to the porous silica particles, kneading, and drying.

[0062] The treatment with hexamethyldisilazane can increase the hydrophobicity of the surface of the porous silica particles, make the surface hydrophobic, and better increase the dispersibility and fluidity of the toner.

[0063] Based on the above embodiments, the present invention provides a spherical silica particle. The average particle size of the spherical silica particle is 50 - 300 nm, and the pore diameter of the spherical silica particle is 0.5 - 2 nm.

[0064] As a preference for the above spherical silica particle, the average particle size of the spherical silica particle is 50 - 100 nm.

[0065] Based on the above embodiments, the present invention provides an application of a spherical silica particle as an external additive particle for toner.

[0066] If silica spheres with high water absorption are added to the toner, the silica spheres with high water absorption can adsorb water molecules under high humidity conditions, prevent the charge amount of the toner from decreasing, ensure the charge stability of the toner, and at the same time, the addition of the silica spheres can increase the dispersibility and fluidity of the toner.

[0067] Based on the above embodiments, the present invention provides an application of a spherical silica particle as an additive for matrix powder. Using the above spherical silica particle as an additive for matrix powder can improve the dispersibility and fluidity of the matrix powder. For example, as an additive for toner, it can improve the dispersibility and fluidity of the toner.

[0068] In the present invention and its embodiments, the spherical polysiloxane powder particles can be obtained according to the existing technology. For example, using methyltrimethoxysilane as the main raw material, referring to the methods in Japanese Patent JP5953942B2 and JP2006117867A, spherical polysiloxane powder particles with an average particle size of 50 - 200 nanometers are prepared.

[0069] In the present invention and its embodiments, the test method for the average particle size (D50) is: detecting with a Beckman particle size analyzer, and measuring the particle size through the spatial distribution (scattering spectrum) of the diffracted or scattered light of the particles; In the present invention and its embodiments, the test method for the average pore diameter is: using a Micromeritics ASAP2460 automatic specific surface area and porosity analyzer to obtain pore diameter data through the Horvath - Kawazoe model.

[0070] In the present invention and its embodiments, the test method for the adsorbed water amount is as follows: After placing the powder particles in an environment with a relative humidity of 75% and a temperature of 40°C for 30 days, the water content of the particles is tested by a Karl Fischer moisture meter at 200°C.

[0071] Example 1 A spherical porous silica particle is provided and prepared according to the following steps: Step 1: Provide spherical polysiloxane particles prepared by condensation using methyltrimethoxysilane as a raw material, with an average particle size of 100 nm.

[0072] Step 2: In an atmosphere furnace, under a nitrogen atmosphere, heat-treat the polysiloxane particles at 1000°C for 3 hours to obtain a carbon-containing silica particle matrix, and sample and detect the carbon content of the silica particle matrix.

[0073] Step 3: In an atmosphere furnace, under an air atmosphere, heat-treat the carbon-containing silica particle matrix at 500°C for 10 hours to obtain porous silica particles.

[0074] Example 2 A spherical porous silica particle is provided and prepared according to the following steps: Step 1: Provide spherical polysiloxane particles prepared by condensation using methyltrimethoxysilane as a raw material, with an average particle size of 100 nm.

[0075] Step 2: In an atmosphere furnace, under a nitrogen atmosphere, heat-treat the polysiloxane particles at 650°C for 3 hours to obtain a carbon-containing silica particle matrix, and sample and detect the carbon content of the silica particle matrix.

[0076] Step 3: In an atmosphere furnace, under an air atmosphere, heat-treat the carbon-containing silica particle matrix at 400°C for 32 hours to obtain porous silica particles.

[0077] Example 3 A spherical porous silica particle is provided and prepared according to the following steps: Step 1: Provide spherical polysiloxane particles prepared by condensation using methyltrimethoxysilane as a raw material, with an average particle size of 100 nm.

[0078] Step 2: In an atmosphere furnace, under a nitrogen atmosphere, heat-treat the polysiloxane particles at 1200°C for 3 hours to obtain a carbon-containing silica particle matrix, and sample and detect the carbon content of the silica particle matrix.

[0079] Step 3: In an atmosphere furnace, under an air atmosphere, heat-treat the carbon-containing silica particle matrix at 800°C for 7 hours to obtain porous silica particles.

[0080] Example 4 A spherical porous silica particle is provided and prepared according to the following steps: Step 1: Provide spherical polysiloxane particles prepared by condensation using methyltrimethoxysilane as a raw material, with an average particle size of 100 nm.

[0081] Step 2: In an atmosphere furnace, under a nitrogen atmosphere, heat-treat the polysiloxane particles at 1000 °C for 3 hours to obtain a carbon-containing silica particle matrix, and sample and detect the carbon content of the silica particle matrix.

[0082] Step 3: In an atmosphere furnace, under an air atmosphere, heat-treat the carbon-containing silica particle matrix at 700 °C for 10 hours to obtain porous silica particles.

[0083] Example 5 A spherical porous silica particle is provided and prepared according to the following steps: Step 1: Provide spherical polysiloxane particles prepared by condensation using methyltrimethoxysilane as a raw material, with an average particle size of 100 nm.

[0084] Step 2: In an atmosphere furnace, under a nitrogen atmosphere, heat-treat the polysiloxane particles at 1000 °C for 3 hours to obtain a carbon-containing silica particle matrix, and sample and detect the carbon content of the silica particle matrix.

[0085] Step 3: In an atmosphere furnace, under an air atmosphere, heat-treat the carbon-containing silica particle matrix at 600 °C for 10 hours to obtain porous silica particles.

[0086] Example 6 A spherical porous silica particle is provided and prepared according to the following steps: Step 1: Provide spherical polysiloxane particles prepared by condensation using methyltrimethoxysilane as a raw material, with an average particle size of 100 nm.

[0087] Step 2: In an atmosphere furnace, under a nitrogen atmosphere, heat-treat the polysiloxane particles at 1000 °C for 3 hours to obtain a carbon-containing silica particle matrix, and sample and detect the carbon content of the silica particle matrix.

[0088] Step 3: In an atmosphere furnace, under an air atmosphere, heat-treat the carbon-containing silica particle matrix at 400 °C for 10 hours to obtain porous silica particles.

[0089] Example 7 A spherical porous silica particle is provided. The difference in the preparation steps compared with Example 1 is that the heat treatment in Step 3 is divided into 2 stages. The specific preparation steps of this example are as follows: Step 1: Provide spherical polysiloxane powder particles containing T units, with an average particle size of 0.1 μm.

[0090] Step 2: In an atmosphere furnace, under a nitrogen atmosphere, heat-treat the polysiloxane particles at 1000 °C for 3 hours to obtain a carbon-containing silica particle matrix, and sample and detect the carbon content of the silica particle matrix.

[0091] Step 3: In an atmosphere furnace, under an air atmosphere, keep the carbon-containing silica particle matrix at 400 °C for 5 hours, and then adjust the temperature of the atmosphere furnace to 600 °C and keep it for 5 hours to obtain porous silica particles.

[0092] Example 8 Provide a spherical porous silica particle. Compared with Example 1 in the preparation steps, the difference is that the heat treatment in Step 3 is divided into 2 stages. The specific preparation steps of this example are as follows: Step 1: Provide spherical polysiloxane powder particles containing T units, with an average particle size of 0.1 μm.

[0093] Step 2: In an atmosphere furnace, under a nitrogen atmosphere, heat-treat the polysiloxane particles at 1000 °C for 3 hours to obtain a carbon-containing silica particle matrix, and sample and detect the carbon content of the silica particle matrix.

[0094] Step 3: In an atmosphere furnace, under an air atmosphere, keep the carbon-containing silica particle matrix at 400 °C for 2 hours, and then adjust the temperature of the atmosphere furnace to 600 °C and keep it for 8 hours to obtain porous silica particles.

[0095] Example 9 Provide a spherical porous silica particle. Compared with Example 1 in the preparation steps, the difference is that the heat treatment in Step 3 is divided into 2 stages. The specific preparation steps of this example are as follows: Step 1: Provide spherical polysiloxane powder particles containing T units, with an average particle size of 0.1 μm.

[0096] Step 2: In an atmosphere furnace, under a nitrogen atmosphere, heat-treat the polysiloxane particles at 1000 °C for 3 hours to obtain a carbon-containing silica particle matrix, and sample and detect the carbon content of the silica particle matrix.

[0097] Step 3: In an atmosphere furnace, under an air atmosphere, keep the carbon-containing silica particle matrix at 500 °C for 8 hours, and then adjust the temperature of the atmosphere furnace to 700 °C and keep it for 24 hours to obtain porous silica particles.

[0098] Example 10 Provide a spherical porous silica particle, which is prepared according to the following steps: Step 1: Provide spherical polysiloxane particles prepared by condensation using methyltrimethoxysilane as a raw material, with an average particle size of 100 nm.

[0099] Step 2: In an atmosphere furnace, under a nitrogen atmosphere, heat-treat the polysiloxane particles at 1000 °C for 7 hours to obtain a carbon-containing silica particle matrix, and sample and detect the carbon content of the silica particle matrix.

[0100] Step 3: In an atmosphere furnace, under an air atmosphere, heat-treat the carbon-containing silica particle matrix at 500 °C for 10 hours to obtain porous silica particles.

[0101] Example 11 Provide a spherical porous silica particle, which is prepared according to the following steps: Step 1: Provide spherical polysiloxane particles prepared by condensation using methyltrimethoxysilane as a raw material, with an average particle size of 100 nm.

[0102] Step 2: In an atmosphere furnace, under a nitrogen atmosphere, heat-treat the polysiloxane particles at 1000 °C for 10 hours to obtain a carbon-containing silica particle matrix, and sample and detect the carbon content of the silica particle matrix.

[0103] Step 3: In an atmosphere furnace, under an air atmosphere, heat-treat the carbon-containing silica particle matrix at 500 °C for 10 hours to obtain porous silica particles.

[0104] Example 12 Provide a spherical porous silica particle, which is prepared according to the following steps: Step 1: Provide spherical polysiloxane particles prepared by condensation using methyltrimethoxysilane as a raw material, with an average particle size of 100 nm.

[0105] Step 2: In an atmosphere furnace, under a nitrogen atmosphere, heat-treat the polysiloxane particles at 1000 °C for 20 hours to obtain a carbon-containing silica particle matrix, and sample and detect the carbon content of the silica particle matrix.

[0106] Step 3: In an atmosphere furnace, under an air atmosphere, heat-treat the carbon-containing silica particle matrix at 500 °C for 10 hours to obtain porous silica particles.

[0107] Example 13 Provide a spherical porous silica particle, which is prepared according to the following steps: Step 1: Provide spherical polysiloxane particles prepared by condensation using methyltrimethoxysilane as a raw material, with an average particle size of 100 nm.

[0108] Step 2: In an atmosphere furnace, under a nitrogen atmosphere, heat the polysiloxane particles at 1000 °C for 3 hours to obtain a carbon-containing silica particle matrix, and take a sample to detect the carbon content of the silica particle matrix.

[0109] Step 3: In an atmosphere furnace, under an air atmosphere, heat the carbon-containing silica particle matrix at 800 °C for 10 hours to obtain porous silica particles.

[0110] Example 14 Provide a spherical porous silica particle, which is prepared according to the following steps: Step 1: Provide a spherical polysiloxane particle prepared by condensation using methyltrimethoxysilane as a raw material, with an average particle size of 50 nm.

[0111] Step 2: In an atmosphere furnace, under a nitrogen atmosphere, heat the polysiloxane particles at 1000 °C for 3 hours to obtain a carbon-containing silica particle matrix, and take a sample to detect the carbon content of the silica particle matrix.

[0112] Step 3: In an atmosphere furnace, under an air atmosphere, heat the carbon-containing silica particle matrix at 500 °C for 10 hours to obtain porous silica particles.

[0113] Example 15 Provide a spherical porous silica particle, which is prepared according to the following steps: Step 1: Provide a spherical polysiloxane particle prepared by condensation using methyltrimethoxysilane as a raw material, with an average particle size of 75 nm.

[0114] Step 2: In an atmosphere furnace, under a nitrogen atmosphere, heat the polysiloxane particles at 1000 °C for 3 hours to obtain a carbon-containing silica particle matrix, and take a sample to detect the carbon content of the silica particle matrix.

[0115] Step 3: In an atmosphere furnace, under an air atmosphere, heat the carbon-containing silica particle matrix at 500 °C for 10 hours to obtain porous silica particles.

[0116] Example 16 Provide a spherical porous silica particle, which is prepared according to the following steps: Step 1: Provide a spherical polysiloxane particle prepared by condensation using methyltrimethoxysilane as a raw material, with an average particle size of 120 nm.

[0117] Step 2: In an atmosphere furnace, under a nitrogen atmosphere, heat the polysiloxane particles at 1000 °C for 3 hours to obtain a carbon-containing silica particle matrix, and take a sample to detect the carbon content of the silica particle matrix.

[0118] Step 3: In an atmosphere furnace, under an air atmosphere, heat-treat the carbon-containing silica particle matrix at 500 °C for 10 hours to obtain porous silica particles.

[0119] Example 17 Provide a spherical porous silica particle, which is prepared according to the following steps: Step 1: Provide a spherical polysiloxane particle prepared by condensation using methyltrimethoxysilane as a raw material, with an average particle size of 200 nm.

[0120] Step 2: In an atmosphere furnace, under a nitrogen atmosphere, heat-treat the polysiloxane particles at 1000 °C for 3 hours to obtain a carbon-containing silica particle matrix, and sample and detect the carbon content of the silica particle matrix.

[0121] Step 3: In an atmosphere furnace, under an air atmosphere, heat-treat the carbon-containing silica particle matrix at 500 °C for 10 hours to obtain porous silica particles.

[0122] Example 18 Provide a spherical porous silica particle, which is prepared according to the following steps: Step 1: Provide a spherical polysiloxane particle prepared by condensation using methyltrimethoxysilane as a raw material, with an average particle size of 300 nm.

[0123] Step 2: In an atmosphere furnace, under a nitrogen atmosphere, heat-treat the polysiloxane particles at 1000 °C for 3 hours to obtain a carbon-containing silica particle matrix, and sample and detect the carbon content of the silica particle matrix.

[0124] Step 3: In an atmosphere furnace, under an air atmosphere, heat-treat the carbon-containing silica particle matrix at 500 °C for 10 hours to obtain porous silica particles.

[0125] Comparative Example 1 Provide a spherical porous silica particle. The preparation steps are the same as those in Example 1, except that: the heat-treatment time in Step 2 is 30 hours.

[0126] Comparative Example 2 Provide a spherical porous silica particle. The preparation steps are the same as those in Example 1, except that: the heat-treatment time in Step 2 is 2 hours.

[0127] Comparative Example 3 Provide a spherical silica particle. The preparation steps are the same as those in Example 1, except that: the heat-treatment temperature in Step 2 is 600 °C.

[0128] Comparative Example 4 A spherical silica particle is provided. The preparation steps are the same as those in Example 1, except that: the heat treatment temperature in Step 2 is 1300 °C.

[0129] Comparative Example 5 A spherical silica particle is provided. The preparation steps are the same as those in Example 1, except that: the heat treatment temperature in Step 3 is 300 °C.

[0130] Comparative Example 6 A spherical silica particle is provided. The preparation steps are the same as those in Example 1, except that: the heat treatment temperature in Step 3 is 850 °C.

[0131] Comparative Example 7 A spherical silica particle is provided. The preparation steps are the same as those in Example 1, except that: the heat treatment temperature in Step 3 is 900 °C.

[0132] Comparative Example 8 A spherical silica particle is provided. The preparation steps are the same as those in Example 1, except that: the heat treatment temperature in Step 3 is 1000 °C.

[0133] Comparative Example 9 A spherical silica particle is provided. The preparation steps are the same as those in Example 1, except that: the heat treatment atmosphere in Step 2 is air.

[0134] Comparative Example 10 A spherical silica particle is provided. The preparation steps are the same as those in Example 1, except that: the heat treatment atmosphere in Step 3 is nitrogen.

[0135] Performance Characterization Record the process parameters of Step 1, Step 2, and Step 3 in the preparation processes of Examples 1 to 18 and Comparative Examples 1 to 10 in Table 1. Then, take the obtained silica particles for testing the average particle size (D50), average pore size, and water adsorption capacity, and record the test results in Table 1. Among them, the temperature difference refers to the temperature difference between the heat treatments in Step 3 and Step 2. The average temperature difference is calculated for the temperature difference between Step 3 and Step 2 in Examples 7 to 9. For example, the temperature difference in Example 7 is ((1000 - 400) + (1000 - 600)) / 2 = 500 °C.

[0136] Table 1 Perform the following analysis based on the data shown in Table 1: As can be seen from Table 1, the preparation of a porous structure in silica particles can be achieved by the two-step heat treatment method provided by the present invention, so that even silica particles with a particle size less than 200 nm can have relatively large pores, and the diameter of the pores can also reach the range of 0.5 - 2 nm. Furthermore, the present invention can greatly increase the water adsorption capacity in silica by increasing the pore diameter in small-sized silica particles.

[0137] From the comparative analysis of Example 1 with Comparative Example 1 and Comparative Example 2, it can be seen that in order to form relatively large pores in silica particles, the carbon content of the carbon-containing silica particle matrix needs to be 8.3 - 16.5 wt%. The reason is as follows: If the carbon content of the carbon-containing silica particle matrix exceeds 16.5 wt%, when too much carbon reacts with oxygen to form carbon dioxide, a large amount of heat will be rapidly generated in the particles, and these heats will cause the temperature in the particle structure to far exceed 800 °C, thereby causing the silica in the particle structure to be melted. As a result, the molten silica fills the pores to densify the particle product, so that there are very few pores in the particle structure and the pore diameter is extremely small; when the carbon content of the carbon-containing silica particle matrix is less than 8.3 wt%, fewer vacancies are formed in the particles after the carbon is carried away by air, ultimately resulting in fewer pores and a smaller pore diameter in the particle structure.

[0138] Furthermore, from the comparative analysis of Example 1 with Example 2, Example 10, Example 11, and Example 12, it can be seen that the carbon content of the carbon-containing silica particle matrix is preferably 10 - 13 wt%.

[0139] From the comparative analysis of Example 1 and Examples 7 to 9, it can be seen that by further adjusting the heat treatment process under air atmosphere, specifically, first heating the particles at 400 - 500 °C and then at 600 - 800 °C, even silica particles with a small particle size of 100 nm can have relatively large pores, and the diameter of the pores can reach more than 1.5 nm. The reason for this is as follows: First, the silica particles are oxidized for residual organic carbon at a relatively low temperature of 400 - 500 °C, and then the pore structure is stabilized at 600 - 800 °C, which makes it difficult for the moisture in the particles to be carried out in the early stage and relatively quickly in the later stage. The moisture in the particles remains in the particle structure in the early stage, and during this process, the carbon in the particles is carried away relatively slowly by the air, and the stability of the particle structure is relatively good, which is conducive to maintaining the integrity of the positions occupied by carbon, and thus helps to maintain the pores formed after carbon is carried away; in the later stage, it is necessary to quickly carry out the moisture, because as the carbon reacts with the air and is gradually carried away, the reaction will cause the particles to heat up. After a period of time, the temperature of the particles is not at 400 - 500 °C. At this time, the heat treatment environment of the atmosphere furnace is appropriately increased to 600 - 800 °C, and the hot air flow can quickly carry out the water from the particles, which can avoid the heat generated by the reaction of moisture with carbon in the particles, resulting in a rapid temperature rise of the particles; at this time, if the heat treatment environment of the atmosphere furnace is not increased to 600 - 800 °C, the moisture comes out of the particles slowly, and more moisture reacts with carbon in the particles, which will cause the particles to heat up rapidly and bring about partial melting of silica.

[0140] From the comparative analysis of Example 1 and Comparative Example 3 and Comparative Example 4, it can be seen that when the heat treatment step temperature in an inert gas atmosphere is 600 °C and 1300 °C respectively, the pores in the obtained silica particle structure are extremely small. The reason for this is as follows: In order to verify the conjecture, the inventor remade according to the method of Comparative Example 4 and found that the pore diameter of the carbon-containing silica particle matrix obtained in Step 2 of the method of Comparative Example 4 was 0.4 nm when sampled and tested. This shows that when the heat treatment step temperature in an inert gas atmosphere is higher than 1200 °C, the excessively high temperature will cause the water molecule gas in the particles to directly carry away the alkyl carbon, and then directly obtain a dense spherical particle matrix in Step 2; at the same time, the heat treatment step temperature in an inert gas atmosphere cannot be lower than 650 °C. If the temperature is too low, the alkyl carbon in the particles will not be completely carbonized, and these incompletely carbonized alkyls will cause the collapse of the pores in the particles during the next carbonization step, reducing the space in the product particles where water molecules can adhere, and resulting in a low water absorption capacity of the product particles.

[0141] From the comparative analysis of Example 1 and Comparative Example 5, it can be seen that the heat treatment step temperature in an air atmosphere cannot be lower than 400 °C; otherwise, the air cannot completely carry away the carbon in the particle structure, and the pores in the particles are small and few; finally, the small pores in the silica particles will result in a small water absorption capacity of the particles.

[0142] From the comparative analysis of Example 1 and Comparative Example 6, it can be seen that in order to provide a heat treatment step with a large air raid particle and an air atmosphere, the temperature cannot be higher than 800 °C. For example, in the heat treatment at 850 °C in an air atmosphere in Comparative Example 6, the obtained particles will be densified. The reason for the analysis is that when the temperature exceeds 800 °C, the moisture in the particles will be quickly carried out, and when these moisture are carried out, they will quickly carry away carbon. At the same time, the reaction between oxygen and carbon generates heat, and these heats will cause the temperature required for melting silica in the particle structure during heat treatment, generating molten silica liquid. During heat treatment at 850 °C, 900 °C, and 1000 °C in an air atmosphere, after the moisture and oxygen carry away the carbon in the particle structure, the positions originally occupied by carbon are quickly filled with molten silica liquid, seriously densifying the product particles. When the temperature drops to 800 °C or 700 °C, such as in Example 13 and Example 4, the moisture is slowly carried out from the product particles. Coupled with the fact that the particles are also at a lower temperature, even after the carbon in the particles reacts with oxygen, the speed of generating molten silica liquid in the particles also slows down. Under the superposition of the double slowdown, the densification problem can be avoided.

[0143] From the comparative analysis of Example 1 and Comparative Example 9, it can be seen that when directly using air to heat-treat polysiloxane particles in Comparative Example 9, the carbon content of the obtained carbon-containing silica particle matrix is relatively low, indicating that oxygen in the air may directly carry away carbon after decomposing alkyl groups at high temperature, densifying the particles, and thus resulting in fewer and smaller pores in the particles, with a pore diameter of only 0.1 nm, and finally manifested as a low water adsorption capacity of the particles.

[0144] From the comparative analysis of Example 1 and Comparative Example 10, it can be seen that when only using nitrogen inert gas to heat-treat polysiloxane particles in Comparative Example 10, the obtained products have smaller pores. It is speculated that the reason is that in step 3, during heat treatment in a nitrogen atmosphere, carbon cannot be removed from the particles after decomposition and will occupy the positions that need to prepare pore vacancies in the particles, resulting in small particle pores.

[0145] The raw materials and equipment used in the present invention are, unless otherwise specified, common raw materials and equipment in the art; the methods used in the present invention are, unless otherwise specified, conventional methods in the art.

[0146] The above are only the preferred embodiments of the present invention and do not impose any limitations on the present invention. Any simple modifications, changes, and equivalent transformations made to the above embodiments according to the technical essence of the present invention still fall within the protection scope of the technical solution of the present invention.

Claims

1. A method for preparing spherical silica particles, characterized in that: It includes the following steps: Step S1: Under an inert gas atmosphere, the polysiloxane particles are heat-treated to form a carbon-containing silica particle matrix with a carbon content of 8.3 - 16.5 wt%. Step S2: Under an air atmosphere, the carbon-containing silica particle matrix is heat-treated at a temperature of 400 - 800 °C to obtain porous spherical silica particles.

2. The preparation method according to claim 1, wherein: The carbon content of the carbon-containing silica particle matrix is 10 - 13 wt%.

3. The preparation method according to claim 1, wherein: The average particle size of the porous spherical silica particles is 50 - 300 nm.

4. The preparation method according to claim 1, characterized in that: The heat treatment temperature in Step S1 is 650 - 1200 °C, and the heat treatment time is 3 - 20 hours.

5. The preparation method according to claim 1 or 4, characterized in that: The temperature difference between the heat treatments in Step S1 and Step S2 is 250 - 600 °C.

6. The preparation method according to claim 1 or 4, characterized in that: The heat treatment in Step S2 is divided into the following two stages: The first stage: Oxidize the residual organic matter at 400 - 500 °C, and keep the temperature for 2 - 8 hours; The second stage: Stabilize the pore structure at 600 - 800 °C, and keep the temperature for 5 - 24 hours.

7. The preparation method according to claim 1, characterized in that: The polysiloxane is a spherical polysiloxane containing T units, and the T units are R1SiO3 - , where R1 is a hydrocarbon group having 1 to 18 carbon atoms or a hydrogen atom.

8. The preparation method according to claim 1, characterized in that: It also includes the following step: The porous spherical silica particles are surface-treated with hexamethyldisilazane.

9. Spherical silica particles prepared by the preparation method according to any one of claims 1 to 8, characterized in that: The average particle size of the spherical silica particles is 50 - 300 nm, and the pore diameter of the spherical silica particles is 0.5 - 2 nm.

10. The spherical silica particles according to claim 9, wherein: The average particle size of the spherical silica particles is 50 - 100 nm.

11. Application of the spherical silica particles prepared by the preparation method according to any one of claims 1 - 8 as an external additive particle for carbon powder.

12. Application of the spherical silica particles prepared by the preparation method according to any one of claims 1 - 8 as a matrix powder additive.

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