High flow narrow dispersed silicone microspheres and ambient pressure method of making same

Abstract

The application discloses a kind of high flowability narrow dispersion organic silicon microspheres, by three functional alkoxy silane and two functional alkoxy silane copolymerization crosslinking three-dimensional skeleton structure is formed, microsphere surface chemical bond grafts hydrophobic alkyl end-capped layer;According to mass parts, preparation raw material includes: three functional alkoxy silane 60~95 parts, two functional alkoxy silane 5~40 parts, three functional alkyl silane 2~6 parts, anhydrous ethanol 70~120 parts, deionized water 25~45 parts, acidic catalyst 0.3~1.2 parts, basic catalyst 3~8 parts, dispersion stabilizer 0.15~0.4 parts.The performance parameters of the organic silicon microspheres are: volume average particle size 5~10 μm, particle size distribution index Span<0.6, sphericity ≥98%, powder angle of repose ≤32°.A kind of normal pressure preparation method of the organic silicon microspheres is also provided, which can realize low-cost, safety and stable mass production of organic silicon microspheres.

Description

Technical Field

[0001] This invention relates to the field of organosilicon functional microsphere preparation technology, specifically to a high-flowability, narrow-dispersion organosilicon microsphere and its preparation method under normal pressure. Background Technology

[0002] Organosilicon microspheres possess excellent properties such as resistance to high and low temperatures, low expansion, high insulation, and spherical ball lubrication, making them a core functional filler for semiconductor packaging, thermally conductive composite materials, optical materials, and modified plastics.

[0003] Existing technologies for preparing organosilicon microspheres have significant drawbacks: First, the microsphere surface retains a large number of silanol groups, resulting in strong interparticle hydrogen bonding and a tendency to agglomerate. This leads to poor powder flowability, a large angle of repose, and an inability to achieve high-proportion filling of the resin system. Under high-filling conditions, the system viscosity increases sharply, severely affecting product processing performance. Second, traditional preparation processes often employ high-pressure closed-loop reactions or one-step rapid condensation processes, which not only involve large equipment investments and low production safety but also produce products with wide particle size distribution, poor sphericity, and poor batch stability. Third, conventional physical coating modification has poor durability and is prone to failure and moisture reabsorption after long-term use, failing to completely solve the powder agglomeration problem. In short, existing organosilicon microsphere technologies suffer from poor flowability, poor dispersibility, stringent preparation processes, and significant challenges in mass production.

[0004] Therefore, there is an urgent need in this technical field to develop a method for preparing organosilicon microspheres that has excellent flowability, uniform particle size distribution, safe and controllable process, and can be industrially mass-produced. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a high-flowability, narrow-dispersion organosilicon microsphere and its preparation method under normal pressure, so as to achieve low-cost, safe and stable mass production of organosilicon microspheres and overcome the defects of the prior art.

[0006] To address the aforementioned technical problems, the present invention provides high-flowability, narrow-dispersion organosilicon microspheres, which are formed by the copolymerization and crosslinking of trifunctional alkoxysilanes and difunctional alkoxysilanes to create a three-dimensional framework structure, with hydrophobic alkyl end-capping layers chemically grafted onto the surface of the microspheres. The raw materials, by mass, include: 60-95 parts of trifunctional alkoxysilane, 5-40 parts of difunctional alkoxysilane, 2-6 parts of trifunctional alkylsilane, 70-120 parts of anhydrous ethanol, 25-45 parts of deionized water, 0.3-1.2 parts of acidic catalyst, 3-8 parts of alkaline catalyst, and 0.15-0.4 parts of dispersion stabilizer.

[0007] The performance parameters of the organosilicon microspheres are as follows: volume average particle size 5-10 μm, particle size distribution index Span < 0.6, sphericity ≥ 98%, powder repose angle ≤ 32°, surface free silanol content < 0.08 mmol / g, and internal porosity < 1.2%.

[0008] The trifunctional alkoxysilane is alkyltrimethoxysilane or methyltriethoxysilane; the alkyltrimethoxysilane is methyltrimethoxysilane or octyltrimethoxysilane or hexadecyltrimethoxysilane; the difunctional alkoxysilane is dimethyldimethoxysilane; the trifunctional alkylsilane is octyltrimethoxysilane or hexadecyltrimethoxysilane.

[0009] The acidic catalyst is at least one of glacial acetic acid, dilute hydrochloric acid, and dilute sulfuric acid.

[0010] The alkaline catalyst is at least one of ammonia water, sodium hydroxide solution, and potassium hydroxide solution with a mass concentration of 25%.

[0011] The dispersant stabilizer is at least one of polyethylene glycol octylphenyl ether, isotridecyl alcohol polyoxyethylene ether, fatty alcohol polyoxyethylene ether, secondary alcohol polyoxyethylene ether, and lauryl alcohol polyether.

[0012] The present invention provides a method for preparing high-flowability, narrow-dispersion organosilicon microspheres under ambient pressure. All reaction steps are carried out under ambient pressure reflux conditions, eliminating the need for high-pressure sealed equipment. The method includes the following steps:

[0013] (1) Atmospheric pressure pre-hydrolysis: Under inert gas protection, anhydrous ethanol and deionized water are mixed, acid is added to adjust the pH of the system to 3.0-4.5, and then a dispersant stabilizer is added and stirred evenly; trifunctional alkoxysilane and difunctional alkoxysilane are mixed and added dropwise to the dispersion system at a uniform rate, and hydrolyzed at room temperature and pressure for 2-2.5 hours;

[0014] (2) Low-temperature pre-condensation: The hydrolysate was heated to 65°C and refluxed at normal pressure. An alkaline catalyst was added dropwise to adjust the pH of the system to 8-9. The reaction was carried out at a constant temperature and stirred for 3 hours to prepare primary microspheres.

[0015] (3) Densification and cross-linking condensation: Continue heating to 80-85℃ and reflux at normal pressure to maintain the alkaline environment of the system. Stir the reaction for 7-9 hours to achieve full cross-linking and densification inside the microspheres;

[0016] (4) In-situ surface modification: The system is cooled to 50-55℃, trifunctional alkylsilane is added, and the reaction is carried out at normal pressure for 3-3.5h to complete the hydroxyl grafting and end-capping modification of the microsphere surface;

[0017] (5) Post-processing and purification: The reaction solution is cooled to room temperature, the microspheres are separated by centrifugation, and after being washed alternately with anhydrous ethanol and deionized water, dried under low temperature vacuum and air flow classification, high-flowability narrow-dispersion organosilicon microspheres are obtained.

[0018] In step (1), the hydrolysis stirring speed is 220-280 rpm.

[0019] In steps (2) and (3), the stirring speed for the condensation reaction is 150 to 200 rpm.

[0020] In step (5), the vacuum drying temperature is 50-65℃.

[0021] By adopting the technical solution of the present invention, the following significant technical effects can be achieved:

[0022] 1. Excellent powder properties: The organosilicon microspheres prepared by this invention have high sphericity, good monodispersity of particle size, no exposed polar silanol groups on the surface, and the particle agglomeration phenomenon is completely improved. They have good flowability, an angle of repose of ≤32°, and high bulk density. They can still maintain low viscosity in resin systems with high filling, and the processing performance is greatly improved.

[0023] 2. Strong structural stability: Rigid monomers ensure the complete spherical structure of the microspheres, while flexible monomers optimize the internal cross-linking network, preventing the microspheres from breaking under pressure and producing fine powder. The product has excellent mechanical stability and durability.

[0024] 3. Safe and easy to mass-produce: The highest reaction temperature throughout the process is only 85℃. All processes can be completed under normal pressure reflux, without the need for high-pressure sealed special equipment such as autoclaves. The production is safe, energy consumption is low, equipment is highly versatile, and it can be mass-produced industrially.

[0025] 4. Long-lasting modification effect: Chemical grafting modification is used instead of traditional physical coating. The hydrophobic alkyl chains are firmly bonded to the surface of the microspheres, and the product does not become damp or clump during long-term storage, resulting in good batch consistency. Attached Figure Description

[0026] Figure 1 This is a scanning electron microscope image of Embodiment 1 of the present invention;

[0027] Figure 2 This is a particle size distribution diagram of Embodiment 1 of the present invention;

[0028] Figure 3 This is a scanning electron microscope image of Embodiment 2 of the present invention;

[0029] Figure 4 This is a particle size distribution diagram of Embodiment 2 of the present invention;

[0030] Figure 5 This is a comparative scanning electron microscope image of the present invention;

[0031] Figure 6 This is a comparative particle size distribution diagram of the present invention. Detailed Implementation

[0032] The method of the present invention will be described in detail below with reference to the embodiments.

[0033] Example 1

[0034] A type of highly fluid, narrowly dispersed organosilicon microsphere is prepared from the following raw materials in parts by weight: 90 parts of methyltrimethoxysilane, 10 parts of dimethyldimethoxysilane, 4 parts of octyltrimethoxysilane, 95 parts of anhydrous ethanol, 35 parts of deionized water, 0.6 parts of glacial acetic acid, 5 parts of 25% ammonia, and 0.25 parts of polyethylene glycol octylphenyl ether.

[0035] Preparation method:

[0036] (1) Under nitrogen protection, mix ethanol and deionized water, add glacial acetic acid to adjust pH=3.8, add dispersant and stabilizer and stir for 20 min; add mixed silane monomer dropwise at a uniform rate, stir at 250 rpm at room temperature for 2 h for hydrolysis;

[0037] (2) Heat to 65℃ and reflux at normal pressure, add ammonia dropwise to adjust pH=8.4, and react at constant temperature for 3h;

[0038] (3) Heat to 83℃ and reflux at normal pressure, then keep warm for 8 hours to condense;

[0039] (4) Cool down to 55°C, add octyltrimethoxysilane, and keep the temperature for 3 hours.

[0040] (5) Cool and centrifuge, wash with ethanol and pure water alternately 4 times, vacuum dry at 60℃ and air classify to obtain the finished microspheres.

[0041] The product test results in this embodiment are as follows: average particle size 5.914 μm, span = 0.571, sphericity 99%, angle of repose 31°, and surface free hydroxyl content 0.06 mmol / g. Under the same filling ratio, the viscosity of the resin system is reduced by 58% compared with ordinary organosilicon microspheres.

[0042] Example 2

[0043] A type of highly fluid, narrowly dispersed organosilicon microsphere is prepared from the following raw materials in parts by weight: 80 parts of methyltriethoxysilane, 8 parts of dimethyldimethoxysilane, 4 parts of hexadecyltrimethoxysilane, 85 parts of anhydrous ethanol, 35 parts of deionized water, 0.5 parts of dilute hydrochloric acid, 4 parts of 8% sodium hydroxide solution, and 0.2 parts of fatty alcohol polyoxyethylene ether.

[0044] Preparation method:

[0045] (1) Under nitrogen protection, mix ethanol and deionized water, add glacial acetic acid to adjust pH=3.5, add dispersant and stabilizer and stir for 25 min; add mixed silane monomer dropwise at a uniform rate and stir at 260 rpm at room temperature for 2.5 h to hydrolyze;

[0046] (2) Heat to 63℃ and reflux at normal pressure, add ammonia dropwise to adjust pH=8.8, and react at constant temperature for 3h;

[0047] (3) Heat to 80℃ and reflux at normal pressure, then hold for condensation for 8.5 hours;

[0048] (4) Cool down to 53°C, add hexadecyltrimethoxysilane, and keep the reaction at this temperature for 3.5 h;

[0049] (5) Cool and centrifuge, wash with ethanol and pure water alternately 4 times, vacuum dry at 55℃ and air classify to obtain the finished microspheres.

[0050] The product test results in this embodiment are as follows: average particle size 6.215 μm, span = 0.576, sphericity 98%, angle of repose 30°, and surface free hydroxyl content 0.05 mmol / g. Under the same filling ratio, the viscosity of the resin system is reduced by 60% compared with ordinary organosilicon microspheres.

[0051] Comparative Example

[0052] Ordinary organosilicon microspheres were prepared by one-step high-compression polymerization using pure methyltrimethoxysilane, without flexible monomer modification or alkyl end-capping treatment. The product has a repose angle of 46°, a wide particle size distribution, and the powder is prone to agglomeration and breakage. The viscosity of the highly filled resin system is significantly high, which cannot meet the processing requirements of high-end materials.

Claims

1. A high-flowability, narrowly dispersed organosilicon microsphere, characterized in that: The organosilicon microspheres are formed by cross-linking trifunctional alkoxysilanes and difunctional alkoxysilanes to form a three-dimensional framework structure, with hydrophobic alkyl end-capping layers chemically grafted onto the surface of the microspheres. The raw materials for preparation include, by mass, 60-95 parts of trifunctional alkoxysilane, 5-40 parts of difunctional alkoxysilane, 2-6 parts of trifunctional alkylsilane, 70-120 parts of anhydrous ethanol, 25-45 parts of deionized water, 0.3-1.2 parts of acidic catalyst, 3-8 parts of alkaline catalyst, and 0.15-0.4 parts of dispersant stabilizer.

2. The high-flowability, narrow-dispersion organosilicon microspheres according to claim 1, characterized in that: The performance parameters of the organosilicon microspheres are as follows: volume average particle size 5-10 μm, particle size distribution index Span < 0.6, sphericity ≥ 98%, powder repose angle ≤ 32°, surface free silanol content < 0.08 mmol / g, and internal porosity < 1.2%.

3. The high-flowability, narrow-dispersion organosilicon microspheres according to claim 1, characterized in that: The trifunctional alkoxysilane is alkyltrimethoxysilane or methyltriethoxysilane; the alkyltrimethoxysilane is methyltrimethoxysilane or octyltrimethoxysilane or hexadecyltrimethoxysilane; the difunctional alkoxysilane is dimethyldimethoxysilane; the trifunctional alkylsilane is octyltrimethoxysilane or hexadecyltrimethoxysilane.

4. The high-flowability, narrow-dispersion organosilicon microspheres according to claim 1, characterized in that: The acidic catalyst is at least one of glacial acetic acid, dilute hydrochloric acid, and dilute sulfuric acid.

5. The high-flowability, narrow-dispersion organosilicon microspheres according to claim 1, characterized in that: The alkaline catalyst is at least one of ammonia water, sodium hydroxide solution, and potassium hydroxide solution with a mass concentration of 25%.

6. The high-flowability, narrow-dispersion organosilicon microspheres according to claim 1, characterized in that: The dispersant stabilizer is at least one of polyethylene glycol octylphenyl ether, isotridecyl alcohol polyoxyethylene ether, fatty alcohol polyoxyethylene ether, secondary alcohol polyoxyethylene ether, and lauryl alcohol polyether.

7. A method for preparing high-flowability, narrow-dispersion organosilicon microspheres according to any one of claims 1-6 under ambient pressure, characterized in that... Includes the following steps: (1) Atmospheric pressure pre-hydrolysis: Under inert gas protection, anhydrous ethanol and deionized water are mixed, acid is added to adjust the pH of the system to 3.0-4.5, and then a dispersant stabilizer is added and stirred evenly; trifunctional alkoxysilane and difunctional alkoxysilane are mixed and added dropwise to the dispersion system at a uniform rate, and hydrolyzed at room temperature and pressure for 2-2.5 hours; (2) Low-temperature pre-condensation: The hydrolysate was heated to 65°C and refluxed at normal pressure. An alkaline catalyst was added dropwise to adjust the pH of the system to 8-9. The reaction was carried out at a constant temperature and stirred for 3 hours to prepare primary microspheres. (3) Densification and cross-linking condensation: Continue heating to 80-85℃ and reflux at normal pressure to maintain the alkaline environment of the system. Stir the reaction for 7-9 hours to achieve full cross-linking and densification inside the microspheres; (4) In-situ surface modification: The system is cooled to 50-55℃, trifunctional alkylsilane is added, and the reaction is carried out at normal pressure for 3-3.5h to complete the hydroxyl grafting and end-capping modification of the microsphere surface; (5) Post-processing and purification: The reaction solution is cooled to room temperature, the microspheres are separated by centrifugation, and after being washed alternately with anhydrous ethanol and deionized water, dried under low temperature vacuum and air flow classification, high-flowability narrow-dispersion organosilicon microspheres are obtained.

8. The method according to claim 7, characterized in that: In step (1), the hydrolysis stirring speed is 220-280 rpm.

9. The method according to claim 7, characterized in that: In steps (2) and (3), the stirring speed for the condensation reaction is 150 to 200 rpm.

10. The method according to claim 7, characterized in that: In step (5), the vacuum drying temperature is 50-65℃.

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