Surface modification method of submicron narrow-distribution silica powder

Abstract

The invention discloses a surface modification method of submicron narrow-distribution silica powder, which comprises the following steps: uniformly mixing a high-boiling-point organic solvent, submicron spherical silica powder and a modifier according to the ratio of (40-70): (30-59): (0.5-1) to obtain a modified liquid with the solid content of 30-70%, the span of the submicron spherical silica powder being below 0.7; the modified liquid is subjected to high-temperature modification, and the viscosity requirement is lt; 500 cp, 500 cp; transferring the modified liquid into a bead mill, and grinding in a nitrogen atmosphere; firstly, the ground modified liquid is concentrated until the solid content is 40%-70%, then the solid content is concentrated until the solid content is 70%-85% in a reduced pressure evaporation and thin film evaporation mode, and finally the solid content is increased to 85% or above in a filtering, vacuum heating concentration or ultrafiltration membrane concentration mode; and heating and drying the concentrated modified liquid to obtain a final product. According to the method, on the premise of simple process, high yield, high efficiency and short production period, the characteristic of narrow particle size distribution of the raw materials can be maintained, and meanwhile, the modification effect can be ensured.

Description

Technical Field

[0001] This invention belongs to the field of inorganic non-metallic materials technology, and specifically relates to a surface modification method for submicron-level narrow-distribution silicon micropowder. Background Technology

[0002] Silicon micropowder possesses advantages such as insulation, thermal stability, and chemical resistance, and is widely used in underfill (UF), epoxy molding compound (EMC), copper clad laminate (CCL), electrical insulation, coatings, and adhesives. With technological advancements, electronic products are becoming increasingly compact—lighter, thinner, shorter, and smaller. Traditional micron-sized spherical silicon can no longer meet the requirements of ultra-thin CCL substrates, while submicron SiO2, with its superior mechanical and processing properties, can fulfill these requirements. Furthermore, in the underfill field, with the development of advanced packaging technologies such as 2.5D / 3D, chips are no longer placed on traditional packaging substrates but are directly bonded to the PCB through silicon interposers. This results in extremely small filling spaces, requiring underfill adhesives to fill these ultra-fine gaps without defects. For silicon micropowder products, the maximum particle size requirement is D100 < 1μm; simultaneously, a concentrated particle size distribution avoids sedimentation or agglomeration problems caused by excessively coarse or fine particles, thus improving stability. Therefore, narrowly distributed silicon micropowder is the future development trend.

[0003] Narrowly distributed submicron-sized silica powder presents significant challenges in dispersion and viscosity control. During dry modification, the flowability of the silica powder changes with factors such as the type of modifier, modification time, and temperature, making it difficult to control the temperature of the modified material. Therefore, wet modification is often used for this type of spherical silica. CN103194097A discloses a method of preparing a nano-silica dispersion using nano-silica, a dispersant, and ethanol. An ultrasonic generator is then inserted into the nano-silica dispersion, and a composite modifier is added for modification, resulting in a modified nano-silica solution. Finally, the modified nano-silica solution is filtered, dried, pulverized, and sieved to obtain modified nano-silica. However, this method's solid-liquid separation process leads to agglomeration and makes it difficult to obtain monodisperse particles. CN103627215A discloses a method for preparing submicron-sized silicon powder using crystalline quartz or fused silica sand as raw materials, combining dry and wet grinding, followed by iron removal and pressure filtration. However, the obtained product has low sphericity and is in filter cake form, requiring further pulverization before use as a filler. JP6933699B2 discloses a method involving heating and mixing submicron-sized silicon powder with deionized water, pre-dispersing it in a sand mill, adding a modifier, wet polishing modification, flash drying, baking, and air jet pulverization to deagglomerate it to the submicron size. This method leads to the modifier reacting and hydrolyzing with water in the system. Water competes with the hydroxyl groups on the surface of the silicon powder, resulting in a large amount of modifier required. Furthermore, the deagglomeration process introduces moisture, affecting product performance. Summary of the Invention

[0004] The technical problem this invention aims to solve is to address the shortcomings of existing technologies by providing a rationally designed surface modification method for submicron-sized narrow-distribution silicon micropowder. This method maintains the narrow particle size distribution of the raw material while ensuring effective modification, provided the process is simple, yields high, efficiency is high, and production cycle is short. Specifically, the particle size distribution has a diameter <1; particle size D100 <1 μm; M value (28~40); chemical coating rate (0.55-0.82); and >20 μm aggregate particle content <100 ppm. The narrow-distribution modified submicron spherical silicon prepared by this method can be used in electronic fields such as UF and CCL.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: A method for surface modification of submicron-sized narrow-distribution silicon micropowder, characterized by the following steps: (1) Preparation of modified solution: Submicron spherical silica powder, high-boiling-point organic solvent and modifier are mixed at a ratio of 40-80:25-59:0.5-1. After uniform mixing, a modified solution with a solid content of 40%-70% is obtained. The median particle size D of the submicron spherical silica powder is... 50 The diameter is 1.0 μm or less, preferably 0.5 μm or less; the radial distance is 0.7, preferably 0.5 or less; (2) High temperature modification: The modified liquid obtained in step (1) is placed in a high temperature equipment at a temperature of 70℃-150℃ and modified at high temperature for 1h-3h. After the modification is completed, the viscosity and flowability are tested. The viscosity requirement is <500cp. (3) Bead milling: The modified liquid obtained in step (2) is transferred into a bead mill and milled under nitrogen atmosphere, with a grinding speed of 1000rpm-2000rpm, a particle size of 0.01mm-10mm, and a linear velocity of 4m / s-12m / s. (4) Concentration: First, concentrate the ground modified liquid to a solid content of 40%-70%, then concentrate it to a solid content of 70%-85% by vacuum evaporation or thin film evaporation, and finally increase the solid content to more than 85% by filtration, vacuum heating concentration or ultrafiltration membrane concentration. (5) Heating and drying: The concentrated modified liquid is heated and dried to obtain the final product.

[0006] The technical problem to be solved by the present invention can also be achieved by the following technical solution: in step (1), the organic solvent is one or more of cyclohexanone, methyl isobutyl ketone, N,N-dimethylformamide, and n-butanol.

[0007] The technical problem to be solved by the present invention can also be achieved by the following technical solution: the modifier is one or more of epoxy group, vinyl group, HMDS, acyl group, phenylamino group, hexylsilane, n-hexylsilane, and tri-tert-butylsilane.

[0008] The technical problem to be solved by the present invention can also be achieved by the following technical solution, wherein the diameter of the submicron spherical silicon powder is preferably less than 0.5.

[0009] The technical problem to be solved by the present invention can also be achieved by the following technical solution: in step (3), the high temperature modification temperature is preferably 100℃-120℃, and more preferably 110℃.

[0010] The technical problem to be solved by the present invention can also be achieved by the following technical solution: in step (3), the viscosity of the modified liquid system after high temperature modification is required to be <100cp.

[0011] The technical problem to be solved by the present invention can also be achieved by the following technical solution: in step (4), the grinding speed is preferably 2500 rpm and the linear velocity is 10 m / s; the feeding method adopts a peristaltic pump, diaphragm pump or magnetic pump; the grinding medium is zirconia balls with a particle size of 0.01 mm-10 mm, preferably 0.05 mm-3 mm, and more preferably 0.1 mm-0.3 mm.

[0012] The technical problem to be solved by the present invention can also be achieved by the following technical solutions: in step (3), the high temperature modification equipment adopts a three-necked flask with a spherical condenser and has a reflux function; in step (4), the heating and drying method adopts blower drying or microwave heating and drying.

[0013] Compared with the prior art, the present invention has the following technical effects: First, by controlling the proportion of the modified liquid components, the solid content of the modified liquid was controlled at 30%-70%, and the viscosity of the modified liquid was <500cp; and a high-boiling-point organic solvent (boiling point >110℃) was used to meet the temperature requirements for the modification effect, and a product with good modification effect was obtained (reflected by M value and chemical coating rate). Secondly, the wet modification method employs high temperature (110℃) and high solid content (70%), which effectively improves the modification effect. By increasing the grinding speed, the particle agglomeration problem of the modified product is avoided, resulting in a smaller silicon micropowder particle size and a smaller amount of agglomerated particles. Third, the solid-liquid separation method is a step-by-step drying method. Filtration is performed first, followed by microwave heating and drying; this can alleviate and solve the agglomeration problem caused by traditional solid-liquid separation (blown air heating and drying). Attached Figure Description

[0014] Figure 1This is a scanning electron microscope image of Embodiment 7 of the present invention; Figure 2 This is the particle size distribution diagram of Example 7; Figure 3 This is the particle size distribution diagram of Example 9; Figure 4 This is a particle size distribution diagram of Example 10; Figure 5 This is the particle size distribution diagram of Example 11; Figure 6 This is a particle size distribution diagram for Comparative Example 1; Figure 7 This is a particle size distribution diagram for Comparative Example 2. Detailed Implementation

[0015] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0016] A method for surface modification of submicron-sized narrow-distribution silicon micropowder, comprising the following steps. (1) Preparation of the modified solution: Submicron spherical silica powder, high-boiling-point organic solvent and modifier are mixed at a ratio of 40-80:25-59:0.5-1. After mixing evenly, a modified solution with a solid content of 40%-70% is obtained. The median particle size D of the submicron spherical silica powder is... 50 The particle size is below 1.0 μm, more preferably below 0.5 μm, and the radial distance is below 0.7, more preferably below 0.5. The high-boiling-point organic solvent is one or more of cyclohexanone, methyl isobutyl ketone, N,N-dimethylformamide, and n-butanol. The modifier is one or more of epoxy, vinyl, HMDS, acyl, phenylamino, hexylsilane, n-hexylsilane, and tri-tert-butylsilane. (2) High temperature modification: The modified liquid obtained in step (1) is placed in a high temperature device at a temperature of 70℃-150℃ and modified at high temperature for 1h-3h. After the modification is completed, the viscosity and flowability are tested. The viscosity is required to be <500cp, and more preferably <100cp. The modification temperature is preferably 100℃-120℃, and more preferably 110℃. (3) Bead milling: The modified liquid obtained in step (2) is transferred into a bead mill and milled under nitrogen atmosphere, with a grinding speed of 1000rpm-2000rpm, a particle size of 0.01mm-10mm, and a linear velocity of 4m / s-12m / s. (4) Concentration: First, concentrate the ground modified liquid to a solid content of 40%-70%, then concentrate it to a solid content of 70%-85% by vacuum evaporation or thin film evaporation, and finally increase the solid content to more than 85% by filtration, vacuum heating concentration or ultrafiltration membrane concentration. (5) Heating and drying: The concentrated modified liquid is heated and dried to obtain the final product.

[0017] In step (4), the grinding speed is preferably 2500 rpm and the linear velocity is 10 m / s; the feeding method is a peristaltic pump, a diaphragm pump or a magnetic pump; the grinding medium is zirconia balls with a particle size of 0.01 mm-10 mm, preferably 0.05 mm-3 mm, and more preferably 0.1 mm-0.3 mm.

[0018] In step (3), the high-temperature modification equipment is a three-necked flask with a spherical condenser and a reflux function; in step (4), the heating and drying method is blower drying or microwave heating and drying.

[0019] Example 1: Using spherical silica with a narrow distribution, median particle size of 0.45 μm, D90=0.57 (diameter spacing 0.3) as raw material; adding methyl ethyl ketone (MEK) and an epoxy modifier, wherein the ratio of spherical silica to MEK to epoxy modifier is 40:30:0.5, and the solid content is 57%, the mixture is mixed and homogeneous to obtain a modified liquid; The modified liquid was placed in a high-temperature device for high-temperature modification. Due to the boiling point of methyl ethyl ketone, the modification temperature was 80℃ and the time was 3 hours. At this time, the viscosity of the modified liquid was tested to be 270 cp. The high-temperature modified liquid was transferred to a bead mill for dispersion; Under a nitrogen atmosphere, the bead mill linear velocity is 4 m / s; the bead mill grinding media particle size is 1 mm. The product was concentrated and dried using a forced-air heating method. The final product had a particle size of D90=10.2μm, a diameter increased to 21.7, and an M value of 35. The chemical coating rate was 0.35%, the content of particles >20μm was 0.07%, and the concentration of particles >1μm exceeded the test range, i.e., >1000ppm.

[0020] Example 2: Using narrowly distributed spherical silica with a median particle size of 0.45 μm and D90=0.57 (diameter spacing 0.3) as raw material, methyl isobutyl ketone and epoxy modifier were added, wherein the ratio of spherical silica to methyl isobutyl ketone to epoxy modifier was 50:40:1 and the solid content was 55%. The mixture was mixed and homogeneous to obtain a modified liquid.

[0021] The modified liquid was placed in a high-temperature device for high-temperature modification. The modification temperature was set to 90℃ and the time was 3 hours. At this time, the viscosity of the modified liquid was tested to be 120 cp. The high-temperature modified liquid was transferred to a bead mill for dispersion; Under a nitrogen atmosphere, the bead mill linear velocity is 5 m / s; the bead mill grinding media particle size is 1 mm. The product was concentrated and dried using a forced-air heating method. The final product had a particle size distribution of D90=15.5μm, a diameter increased to 33.4, and an M value of 55. The chemical coating rate was 0.45%, the content of particles >20μm was 0.08%, and the concentration of particles >1μm exceeded the test range, i.e., >1000ppm.

[0022] Example 3: Using spherical silica with a narrow distribution, median particle size of 0.45 μm, D90=0.57 (diameter spacing 0.3) as raw material; cyclohexanone and aniline modifier were added, wherein the ratio of spherical silica:cyclohexanone:aniline modifier = 80:55:0.8, the solid content was 59%, and the mixture was mixed evenly to obtain a modified liquid; The modified liquid was placed in a high-temperature device for high-temperature modification. The modification temperature was set to 110℃ and the time was 3 hours. At this time, the viscosity of the modified liquid was tested to be 50 cp. The high-temperature modified liquid was transferred to a bead mill for dispersion; Under a nitrogen atmosphere, the bead mill linear velocity is 8 m / s; the bead mill grinding media particle size is 1 mm. The product was concentrated and dried using a forced-air heating method. The final product had a particle size distribution of D90=22.4μm, a diameter increased to 48.8, and an M value of 55. The chemical coating rate was 0.55, the content of particles >20μm was 0.1%, and the concentration of particles >1μm exceeded the test range, i.e., >1000ppm.

[0023] Example 4: Using spherical silica with a narrow distribution, median particle size of 0.45 μm, D90=0.57 (diameter spacing 0.3) as raw material; n-butanol and aniline modifier were added, wherein the ratio of spherical silica:n-butanol:aniline modifier = 40:50:0.5, the solid content was 44.2%, and the mixture was mixed evenly to obtain a modified solution; The modified liquid was placed in a high-temperature device for high-temperature modification. The modification temperature was set to 110℃ and the time was 3 hours. At this time, the viscosity of the modified liquid was tested to be 50 cp. The high-temperature modified liquid was transferred to a bead mill for dispersion; Under a nitrogen atmosphere, the bead mill linear velocity is 7 m / s; the bead mill grinding media particle size is 1 mm. The product was concentrated and dried using a forced-air heating method. The final product had a particle size distribution of D90=13.3μm, a diameter increased to 28.6, and an M value of 55. The chemical coating rate was 0.6, the content of >20μm aggregated particles was 0.06%, and the concentration of >1μm particles exceeded the test range, i.e., >1000ppm.

[0024] Example 5: Using spherical silica with a narrow distribution, median particle size of 0.45 μm, D90=0.57 (diameter spacing 0.3) as raw material; cyclopentanone and acyloxy modifier were added, wherein the ratio of spherical silica:cyclopentanone:acyloxy modifier = 70:30:0.5, the solid content was 70%, and the mixture was mixed evenly to obtain a modified liquid; The modified liquid was placed in a high-temperature device for high-temperature modification. The modification temperature was set to 110℃ and the time was 3 hours. At this time, the viscosity of the modified liquid was tested to be 50 cp. The high-temperature modified liquid was transferred to a bead mill for dispersion; Under a nitrogen atmosphere, the bead milling linear velocity is 10 m / s; the bead milling media particle size is 0.1 mm. The product was concentrated and dried using a forced-air heating method. The final product had a particle size distribution of D90=8.3μm, a diameter increased to 17.4, and an M value of 60; a chemical coating rate of 0.65; a content of >20μm aggregated particles of 0.04%; and a concentration of >1μm particles of 800ppm.

[0025] Example 6: Using spherical silica with a narrow distribution, median particle size of 0.45 μm, D90=0.57 (particle size spacing 0.3) as raw material; adding methyl isobutyl ketone and epoxy modifier, wherein the ratio of spherical silica:methyl isobutyl ketone:epoxy modifier = 70:30:0.5, and the solid content is 70%, the mixture is mixed and homogeneous to obtain a modified liquid; The modified liquid was placed in a high-temperature device for high-temperature modification. The modification temperature was set to 110℃ and the time was 3 hours. At this time, the viscosity of the modified liquid was tested to be 50 cp. The high-temperature modified liquid was transferred to a bead mill for dispersion; Under a nitrogen atmosphere, the bead mill linear velocity was 10 m / s; the bead mill media particle size was 0.1 mm; firstly, filtration was used for concentration, increasing the solid content to 85%; then, forced-air heating was used for concentration and drying, and the final product particle size distribution was D90=5.1 μm, the diameter was increased to 10.3, the M value was 60; the chemical coating rate was 0.78, the content of >20 μm aggregated particles was 0.02%; and the concentration of >1 μm particles was 500 ppm.

[0026] Example 7: Using spherical silica (0.3-diameter spacing) with a narrow distribution, median particle size of 0.45 μm, and D90=0.57 as raw material; adding methyl isobutyl ketone and phenylamino modifier, wherein the ratio of spherical silica:methyl isobutyl ketone:phenylamino modifier is 70:30:0.5, and the solid content is 70%, the mixture is mixed and homogeneous to obtain a modified liquid; The modified liquid was placed in a high-temperature device for high-temperature modification. The modification temperature was set to 110℃ and the time was 3 hours. At this time, the viscosity of the modified liquid was tested to be 50 cp. The high-temperature modified liquid was transferred to a bead mill for dispersion; under a nitrogen atmosphere, the bead mill linear velocity was 10 m / s; the bead mill media particle size was 0.1 mm. The solid content was increased to 83% by vacuum evaporation; then the solid content was increased to 87% by filtration; and finally the solid content was increased to 87% by microwave heating. The final product had a particle size distribution of D90=0.6μm, diameter=0.3, M value 65; chemical coating rate of 0.82; content of >20μm aggregated particles of 0.0015%; and concentration of >1μm particles of 35ppm.

[0027] Example 8: Using spherical silica (0.3-diameter spacing) with a narrow distribution, median particle size of 0.45 μm, and D90=0.57 as raw material; adding methyl isobutyl ketone and alkylsilane-n-hexylsilane-tritert-butylsilane modifier, wherein the ratio of spherical silica:methyl isobutyl ketone:alkylsilane-n-hexylsilane-tritert-butylsilane modifier = 70:30:0.5, and the solid content is 70%, the mixture is mixed and homogeneous to obtain a modified solution; The modified liquid was placed in a high-temperature device for high-temperature modification at 110℃ for 3 hours. The viscosity of the modified liquid was measured at 50 cp. The modified liquid was then transferred to a bead mill for dispersion. Under a nitrogen atmosphere, the bead milling linear velocity was 10 m / s, and the bead milling media particle size was 0.1 mm. First, thin-film evaporation was used to increase the solid content to 81%. Then, filtration was used for concentration, increasing the solid content to 84%. Finally, microwave heating was used for concentration and drying. The final product had a particle size distribution of D90 = 0.6 μm, a diameter = 0.3, and an M value of 63; a chemical coating rate of 0.80; a >20 μm aggregate particle content of 0.0015%; and a >1 μm particle concentration of 35 ppm.

[0028] Example 9: Using spherical silica with a narrow distribution, median particle size of 0.33 μm, D90=0.41 (diameter spacing 0.44) as raw material; adding methyl isobutyl ketone and alkylsilane-n-hexylsilane tri-tert-butylsilane modifier, wherein the ratio of spherical silica to methyl isobutyl ketone to alkylsilane-n-hexylsilane tri-tert-butylsilane modifier is 70:30:0.5, and the solid content is 70%, the mixture is mixed and homogeneous to obtain a modified liquid; The modified liquid was placed in a high-temperature device for high-temperature modification at 110℃ for 3 hours. The viscosity of the modified liquid was measured at 50 cp. The modified liquid was then transferred to a bead mill for dispersion. Under a nitrogen atmosphere, the bead milling linear velocity was 10 m / s, and the bead milling media particle size was 0.1 mm. First, thin-film evaporation was used to increase the solid content to 81%. Then, filtration was used for concentration, increasing the solid content to 84%. Finally, microwave heating was used for concentration and drying. The final product had a particle size distribution of D90 = 0.6 μm, a diameter = 0.3, and an M value of 63; a chemical coating rate of 0.80; a >20 μm aggregate particle content of 0.0015%; and a >1 μm particle concentration of 35 ppm.

[0029] Example 10: Using spherical silica (0.47 diameter) with a narrow distribution, median particle size of 0.82 μm, and D90=1.01 as raw material; adding methyl isobutyl ketone and alkylsilane-n-hexylsilane tri-tert-butylsilane modifier, wherein the ratio of spherical silica:methyl isobutyl ketone:alkylsilane-n-hexylsilane tri-tert-butylsilane modifier = 70:30:0.5, and the solid content is 70%, the mixture is mixed and homogeneous to obtain a modified liquid; The modified liquid was placed in a high-temperature device for high-temperature modification at 110℃ for 3 hours. The viscosity of the modified liquid was measured at 50 cp. The modified liquid was then transferred to a bead mill for dispersion. Under a nitrogen atmosphere, the bead milling linear velocity was 10 m / s, and the bead milling media particle size was 0.1 mm. First, thin-film evaporation was used to increase the solid content to 81%. Then, filtration was used for concentration, increasing the solid content to 84%. Finally, microwave heating was used for concentration and drying. The final product had a particle size distribution of D90 = 0.6 μm, a diameter = 0.3, and an M value of 63; a chemical coating rate of 0.80; a >20 μm aggregate particle content of 0.0015%; and a >1 μm particle concentration of 35 ppm.

[0030] Example 11: Using spherical silica with a narrow distribution, median particle size of 0.91 μm, D90=1.17 (diameter spacing 0.68) as raw material; adding methyl isobutyl ketone and alkylsilane-n-hexylsilane tri-tert-butylsilane modifier, wherein the ratio of spherical silica to methyl isobutyl ketone to alkylsilane-n-hexylsilane tri-tert-butylsilane modifier is 70:30:0.5, and the solid content is 70%, the mixture is mixed and homogeneous to obtain a modified liquid; The modified liquid was placed in a high-temperature device for high-temperature modification at 110℃ for 3 hours. The viscosity of the modified liquid was measured at 50 cp. The modified liquid was then transferred to a bead mill for dispersion. Under a nitrogen atmosphere, the bead milling linear velocity was 10 m / s, and the bead milling media particle size was 0.1 mm. First, thin-film evaporation was used to increase the solid content to 81%. Then, filtration was used for concentration, increasing the solid content to 84%. Finally, microwave heating was used for concentration and drying. The final product had a particle size distribution of D90 = 0.6 μm, a diameter = 0.3, and an M value of 63; a chemical coating rate of 0.80; a >20 μm aggregate particle content of 0.0015%; and a >1 μm particle concentration of 35 ppm.

[0031] Comparative Example 1: Using narrowly distributed spherical silica with a median particle size of 0.45 μm and a D90 of 0.57 (particle size spacing of 0.3) as raw material, a high-speed mixer was used with a blade rotation speed of 800 rpm and a linear velocity of 8.4 m / s. Dry modification was performed using an epoxy group modifier, with a treatment group number of 1.0 atoms / nm based on the theoretical specific surface area. 2With the addition of a modifier and a temperature set to 90℃, the final product exhibits a wider particle size distribution, with D90=8.4μm, a diameter increased to 17.7, and an M value of 50; the chemical coating rate is 0.35%, the content of >20μm aggregated particles is 0.08%, and the concentration of >1μm particles exceeds the test range, i.e., >1000ppm.

[0032] Comparative Example 2: Using narrowly distributed spherical silica with a median particle size of 0.45 μm and a D90 of 0.57 (particle size spacing of 0.3) as raw material, a high-speed mixer was used with a blade rotation speed of 800 rpm and a linear velocity of 8.4 m / s. Dry modification was performed using an aniline-based modifier, with a treatment density of 1.0 cells / nm based on the theoretical specific surface area. 2 With the addition of a modifier and a temperature set at 110℃, the final product exhibits a wider particle size distribution, with D90 = 22.2 μm, a diameter increased to 48.3, and an M value of 50. The chemical coating rate is 0.45%, the content of >20 μm aggregated particles is 0.1%, and the concentration of >1 μm particles exceeds the test range, i.e., >1000 ppm.

[0033] Comparative Example 3: Using narrowly distributed spherical silica with a median particle size of 0.45 μm and a D90 of 0.57 (particle size spacing of 0.3) as raw material; methyl ethyl ketone (MEK) and powder were mixed at a ratio of 70:30 according to a solid content of 30%, and a vinyl modifier was added. The modifier was added at a theoretical specific surface area of ​​4.0 cells / nm², and after thorough mixing, a modified liquid was obtained. The modified liquid was placed in a high-temperature device for high-temperature modification. Due to the boiling point of MEK, the modification temperature was 70℃ and the time was 1 hour. At this time, the viscosity of the modified liquid was measured to be 150 cp. The high-temperature modified liquid was transferred to a bead mill for dispersion; under a nitrogen atmosphere, the bead mill linear velocity was 4 m / s; the bead mill media particle size was 1 mm; the product was concentrated and dried by forced-air heating, and the final product particle size D90=5.3 μm, the diameter was increased to 10.8, the M value was 25; the chemical coating rate was 0.25, the content of >20 μm aggregated particles was 0.05%; and the concentration of >1 μm particles was 1000 ppm.

[0034] The wet modification method is limited by the boiling point of the solvent and cannot use high temperature, resulting in a lower modification effect (M value, chemical coating rate) than the dry method.

[0035] The parameter lists for the methods described in Examples 1-8 and Comparative Examples 1-3 are as follows:

[0036] Reference Figure 1-4 The silica powders prepared in Examples 1-8 and Comparative Examples 1-3 were tested, including M value, viscosity, agglomerated particle content, chemical coating rate, and particle concentration. 1. Viscosity testing is needed to control the flowability of the modified liquid. If the M value is low, the solid content must be reduced. The relationship between the M value and solid content is as follows: the larger the M value, the larger the solid content, the better the modification effect, and the higher the utilization rate of the modifier. The higher the chemical coating rate.

[0037] 2. M value: The M value is tested according to CNCN 1816494A "Hydrophobic Pyrolytic Silica". It is used to characterize the hydrophobicity of the product and can indirectly indicate the degree of spherical silicon modification.

[0038] 3. Agglomerated particle content: The method for testing agglomerated particle content is as described in CN 1816494A "Hydrophobic Pyrolysis Silica". However, a 20μm sieve is used for the test. This is used to characterize product agglomeration and serves as a supplement to particle size measurement.

[0039] 4. Chemical coating rate: After modification, the carbon content was tested to obtain m1. After the modified silicon spheres were cleaned with methyl ethyl ketone, the carbon content was tested again to obtain m2. The chemical coating rate was obtained by comparing m2 and m1.

[0040] 5. The concentration of particles >1μm was tested using a Coltter counter manufactured by Beckman Coulter.

[0041] The measurement results are shown in the table below:

[0042] The experimental results above show that: 1. As can be seen from Example 1, wet modification increases the solid content of the modifying liquid and prolongs the modification time. However, due to the boiling point of the solvent, high temperature cannot be used. The modification effect is better than that of Comparative Example 3, but it is still not ideal. 2. As can be seen from Example 2, wet modification and increasing the reaction temperature result in a better modification effect than Comparative Example 3, but agglomeration problems similar to those of dry modification occur, and the particle size deteriorates (the diameter increases and the amount of aggregated particles increases). 3. As can be seen from Examples 4 and 5, by increasing the grinding line speed and using smaller grinding media, the modification effect of Example 5 is better than that of Example 4, and the agglomeration problem is improved (the diameter becomes smaller and the amount of agglomerated particles becomes smaller). 4. As can be seen from Examples 6, 7 and 8, the two-step concentration and drying method, and the microwave heating method for drying, can effectively combat agglomeration.

[0043] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for surface modification of submicron-sized, narrow-distribution, silica micropowder, characterized by, The method comprises the following steps, (1) modified liquid configuration: the sub-micron spherical silica powder, high boiling point organic solvent and modifier are mixed according to 40-80: 25-59: 0.5-1, after mixing uniformly, the modified liquid with solid content of 40%-70% is obtained, the median particle size D 50 of the sub-micron spherical silica powder is 1.0 μm or less, and the span is 0.7 or less; (2) high temperature modification: the modified liquid obtained in step (1) is placed in a high temperature device with a temperature of 70-150°C, and is subjected to high temperature modification for 1-3h, and then the viscosity and fluidity are tested, and the viscosity is required to be <500cp; (3) bead milling: the modified liquid obtained in step (2) is moved into a bead mill, and is ground under the conditions that the grinding speed is 1000-2000rpm, the particle size of the grinding medium is 0.01-10mm, and the linear speed is 4-12m / s under a nitrogen atmosphere; (4) concentration: the ground modified liquid is first concentrated to a solid content of 40-70%, and then is concentrated to a solid content of 70-85% by using a method of reduced pressure evaporation or thin film evaporation, and finally is concentrated to a solid content of more than 85% by using a method of filtration, vacuum heating concentration or ultrafiltration membrane concentration; (5) heating and drying: the concentrated modified liquid is subjected to heating and drying to obtain a final product.

2. The method for surface modification of submicron-sized silicon fine powder with narrow distribution according to claim 1, characterized in that, In step (1), the organic solvent is one or more of cyclohexanone, methyl isobutyl ketone, N,N-dimethylformamide and n-butanol.

3. The method for surface modification of submicron-sized silicon fine powder with narrow distribution according to claim 1, characterized in that, The modifier is one or more of epoxy, vinyl, HMDS, acyl, phenylamino, alkylsilane-n-hexylsilane and tri-tert-butylsilane.

4. The method for surface modification of submicron-sized silicon fine powder with narrow distribution according to claim 1, wherein The median particle size D50 of the submicron spherical silicon micropowder is preferably 0.5 μm or less, and the span is preferably 0.5 or less. 50 The median particle size D50 of the submicron spherical silicon micropowder is preferably 0.5 μm or less, and the span is preferably 0.5 5. The method for surface modification of submicron-sized silicon fine powder with narrow distribution according to claim 1, wherein In step (3), the high temperature modification temperature is preferably 100-120°C.

6. The method for surface modification of submicron-sized silicon fine powder with narrow distribution according to claim 5, wherein In step (3), the high temperature modification temperature is further preferably 110°C.

7. The method according to claim 1, wherein the surface modification is performed by treating the silica powder with a silane coupling agent. In step (3), the viscosity of the modified liquid system after high temperature modification is required to be <100cp.

8. The method for surface modification of submicron-sized silicon fine powder with narrow distribution according to claim 1, wherein In step (4), the grinding speed is preferably 2500rpm, and the linear speed is 10m / s; the feeding mode adopts a peristaltic pump, a diaphragm pump or a magnetic drive pump; the grinding medium is zirconia ball with a particle size of 0.01-10mm, preferably 0.05-3mm.

9. The method according to claim 8, wherein the surface modification is performed by treating the silica micropowder with a silane coupling agent. In step (4), the particle size of the grinding medium is preferably 0.1-0.3mm.

10. The method for surface modification of submicron-sized silicon fine powder with narrow distribution according to claim 1, wherein In step (3), the high temperature modification device adopts a three-necked flask with a spherical condenser and a reflux function; in step (4), the heating and drying mode adopts air drying or microwave heating and drying.

Images