阅读说明：本技术 一种多孔无定型二氧化硅粉体及其制备方法、应用 (Porous amorphous silicon dioxide powder and preparation method and application thereof ) 是由 王韶晖 蒋学鑫 张轲轲 秦永法 于 2020-06-12 设计创作，主要内容包括：本发明公开了一种多孔无定型二氧化硅粉体及其制备方法、应用,涉及二氧化硅粉体技术领域,所述多孔无定型二氧化硅粉体由纳米二氧化硅聚集构成,纳米二氧化硅之间通过化学键连接,形成孔道互穿结构；将本发明制备的粉体作为防沉降剂用在灌封胶中,灌封胶大分子可以通过孔道互联,形成稳定的网络结构；并且少量添加该粉体便可以起到防止导热粉体沉淀的效果,同时对导热灌封胶的整体导热性能、流平性影响小。(The invention discloses porous amorphous silicon dioxide powder and a preparation method and application thereof, relating to the technical field of silicon dioxide powder, wherein the porous amorphous silicon dioxide powder is formed by aggregating nano silicon dioxide, and the nano silicon dioxide is connected with each other through chemical bonds to form a pore interpenetrating structure; the powder prepared by the invention is used in the pouring sealant as an anti-settling agent, and the macromolecules of the pouring sealant can be interconnected through the pore channels to form a stable network structure; and the powder can be added in a small amount to prevent the heat-conducting powder from precipitating, and the influence on the overall heat-conducting performance and the leveling property of the heat-conducting pouring sealant is small.)

1. A porous amorphous silica powder characterized in that: the structure is formed by aggregating nano silicon dioxide, and the nano silicon dioxide is connected with each other through chemical bonds to form a pore interpenetrating structure.

2. The porous amorphous silica powder according to claim 1, characterized in that: the median particle size of the porous amorphous silicon dioxide powder is 1-10 mu m, and the specific surface area is 150-300m²The pore diameter is 2-3 nm.

3. The porous amorphous silica powder according to claim 1, characterized in that: the preparation method of the porous amorphous silicon dioxide powder comprises the following specific steps:

step (1): adding nano silicon dioxide into water, stirring, and starting heating to obtain mixed slurry;

step (2): adjusting the pH value of the slurry;

and (3): adding a coupling agent while stirring for reaction to obtain a reaction product;

and (4): and (3) washing, filtering, drying and crushing the reaction product by ions to obtain the porous amorphous silicon dioxide powder.

4. The porous amorphous silica powder according to claim 3, characterized in that: the mass ratio of the water, the nano silicon dioxide and the coupling agent is 100 (5-15) to 1-6; the heating temperature is 40-80 ℃; the pH value is 1-5; the particle size of the nano silicon dioxide is 5-50 nm; the coupling agent is at least one of silane coupling agent and titanate coupling agent; the reaction time is 8-20 h.

5. The porous amorphous silica powder according to any one of claims 1 to 4, characterized in that: and treating the porous amorphous silicon dioxide powder by using a silane coupling agent to obtain the modified porous amorphous silicon dioxide powder.

6. The porous amorphous silica powder according to claim 5, characterized in that: the silane coupling agent includes but is not limited to at least one of methyltrimethoxysilane, triethoxysilane, vinyltrimethoxysilane, triethoxysilane, aminosilane, phenylaminosilane, epoxysilane, acryloxysilane.

7. Use of the porous amorphous silica powder prepared according to any of claims 1 to 4 as an anti-settling agent in a potting compound containing filler.

8. Use according to claim 7, characterized in that: the filler comprises at least one of quartz powder, aluminum hydroxide, aluminum oxide, magnesium oxide, zinc oxide, silicon nitride, aluminum nitride, boron nitride, titanium dioxide, calcium carbonate, montmorillonite, carbon fiber, graphite, metal powder and the like.

9. Use according to claim 7, characterized in that: the pouring sealant comprises at least one of epoxy resin pouring sealant, silicone rubber pouring sealant and polyurethane pouring sealant.

10. Use according to claim 9, characterized in that: the silicone rubber pouring sealant is a heat-conducting pouring sealant, and the heat-conducting pouring sealant comprises organic silicon gel, heat-conducting powder and porous amorphous silicon dioxide powder, and all the components are mixed in proportion.

11. Use according to claim 10, characterized in that: the heat-conducting pouring sealant also comprises hydrogen-containing silicone oil, a catalyst and an inhibitor.

12. Use according to claim 10, characterized in that: the heat-conducting powder is at least one selected from quartz powder, aluminum hydroxide, aluminum oxide, zinc oxide, magnesium oxide, silicon nitride, aluminum nitride, boron nitride, titanium dioxide, calcium carbonate and montmorillonite.

13. Use of the porous amorphous silica powder prepared according to any one of claims 1 to 4 as an anti-settling agent in aqueous or solvent borne coatings.

The technical field is as follows:

the invention relates to the technical field of silicon dioxide powder, in particular to porous amorphous silicon dioxide powder and a preparation method and application thereof.

Background art:

in the use process of the electronic element, the performance of the electronic element is reduced or damaged due to external factors such as dust, moisture, vibration and the like, and in order to eliminate the external adverse effect, the electronic element is protected by pouring sealant. Since the electronic component emits heat during use, the potting adhesive needs to have good heat conductivity in addition to insulation performance. Particularly, after the 5G era comes, the power and density of electronic components are continuously improved, the heat productivity of the electronic components is higher, and higher requirements on the heat conductivity of the pouring sealant are provided.

In order to improve the heat conductivity of the potting adhesive, the technical personnel adopt a method of adding heat-conducting fillers into the potting adhesive, wherein the heat-conducting fillers mainly comprise heat-conducting ceramic powder, such as quartz powder, aluminum hydroxide, magnesium oxide, aluminum oxide, zinc oxide, aluminum nitride, boron nitride and the like. Due to the very large difference in density between the thermally conductive filler and the polymer, the resulting composite system is an unstable suspension, and the settling rate and tendency are generally more pronounced with larger particle sizes and higher densities of the filler employed.

In order to reduce the sedimentation of the heat-conducting filler, one method is to increase the viscosity of the pouring sealant, but when the viscosity is increased, the leveling property of the pouring sealant is reduced, the space to be filled is difficult to fill smoothly, and the bubbles contained in the pouring sealant are difficult to remove. Another method is to add anti-settling agents, which are mainly nano inorganic materials such as silicon dioxide, titanium dioxide, calcium carbonate, etc. The principle is that the nano inorganic material is dispersed in the pouring sealant, and hydrogen bonds are formed between the surface of the nano inorganic material and the pouring sealant, so that a network effect is formed, and the purpose of preventing the heat-conducting powder from settling is achieved. Since the network effect is achieved by hydrogen bonds, the smaller the particle size, the larger the specific surface area, the more significant the network effect, and vice versa.

The Chinese patent of application No. 2014104939127, entitled "preparation method of Bi-component addition type organosilicon heat-conducting pouring sealant", discloses a preparation method of organosilicon pouring sealant, which adopts nano-silica and the like as additives to weaken the precipitation and hardening phenomena of fillers in the pouring sealant. However, when the nano-scale filler is adopted, the viscosity of the pouring sealant is greatly increased, so that the leveling property of the pouring sealant is reduced. In addition, the nano-scale powder has fine particle size and high surface energy, is easy to agglomerate and is not beneficial to uniform dispersion in a polymer matrix. Although the dispersibility can be improved by the surface treatment process of the nano powder, the agglomeration problem is difficult to fundamentally solve.

The invention content is as follows:

the invention aims to solve the technical problem of providing micron-sized porous amorphous silicon dioxide powder with large specific surface area and a mutual-transmission pore channel structure and a preparation method thereof, and applying the prepared porous amorphous silicon dioxide powder as an anti-settling agent to pouring sealant and water-based or solvent-based paint.

The technical problem to be solved by the invention is realized by adopting the following technical scheme:

the porous amorphous silica powder consists of nanometer silica, and nanometer silica is connected via chemical bond to form interpenetrated pore canal structure.

The median particle size of the porous amorphous silicon dioxide powder is 1-10 mu m, and the specific surface area is 150-300m²The pore diameter is 2-3 nm.

Further, the median particle size of the porous amorphous silica powder is preferably 2 to 5 μm, and the specific surface area is preferably 180-240m²/g。

The preparation method of the porous amorphous silicon dioxide powder comprises the following specific steps:

step (1): adding nano silicon dioxide into water, stirring, and starting heating to obtain mixed slurry;

step (2): adjusting the pH value of the slurry;

and (3): adding a coupling agent while stirring for reaction to obtain a reaction product;

and (4): and (3) washing, filtering, drying and crushing the reaction product by ions to obtain the porous amorphous silicon dioxide powder.

The mass ratio of the water, the nano silicon dioxide and the coupling agent is 100 (5-15) to 1-6.

The heating temperature is 40-80 ℃.

The pH value is 1-5.

The particle size of the nano silicon dioxide is 5-50 nm.

The coupling agent is at least one of silane coupling agent and titanate coupling agent, such as KH540, KH580, KH902, A151, KH171, etc.

The reaction time is 8-20 h.

As shown in fig. 1 and 2, the porous amorphous silica powder is micron-sized, has a large particle size, is easy to disperse, has a uniform particle size, and is structurally stable due to chemical bond connection among nano-silica; the inter-transmission pore canal is formed in the powder, so that the specific surface area is increased. Compared with the conventional silicon dioxide powder prepared by calcination, the preparation method has mild preparation conditions.

The invention also aims to provide application of the prepared porous amorphous silicon dioxide powder, and the powder is used as an anti-settling agent in a pouring sealant containing a filler, so that the settling of the filler can be effectively reduced, and the influence on the leveling property and the heat conductivity of the pouring sealant is small.

The filler comprises at least one of quartz powder, aluminum hydroxide, aluminum oxide, magnesium oxide, zinc oxide, silicon nitride, aluminum nitride, boron nitride, titanium dioxide, calcium carbonate, montmorillonite, carbon fiber, graphite, metal powder and the like.

The pouring sealant comprises at least one of epoxy resin pouring sealant, silicone rubber pouring sealant and polyurethane pouring sealant.

The silicone rubber pouring sealant is a heat-conducting pouring sealant.

The heat-conducting pouring sealant comprises organic silicon gel, heat-conducting powder and porous amorphous silicon dioxide powder, and all the components are mixed in proportion; the curing temperature of the heat-conducting pouring sealant is 120-150 ℃, and the curing time is 5-60 min.

The heat-conducting pouring sealant also comprises hydrogen-containing silicone oil, a catalyst and an inhibitor. Wherein the hydrogen-containing silicone oil is used as a cross-linking agent, and the inhibitor is used for preventing the organic silicon gel from generating cross-linking before encapsulation.

The heat-conducting powder is at least one selected from quartz powder, aluminum hydroxide, aluminum oxide, zinc oxide, magnesium oxide, silicon nitride, aluminum nitride, boron nitride, titanium dioxide, calcium carbonate and montmorillonite.

The mixing is realized by mixing equipment with revolution and rotation mixing functions, and the mixing equipment comprises at least one of a homogenizer, a kneader, an internal mixer and a planetary mixer.

The mixing equipment preferably adopts a homogenizer, and a multi-section mode and a vacuum defoaming mode are adopted in sequence during mixing, wherein the multi-section mode is as follows: the rotation speed is 500-700rpm for 20-60s, the rotation speed is 1000-3000rpm for 10-40s, and the rotation speed is 800-1000rpm for 50-100 s; and (3) vacuum defoaming mode: the rotation speed of 800-.

The modified porous amorphous silica powder is obtained by treating the porous amorphous silica powder with a silane coupling agent, so that the compatibility of the porous amorphous silica powder in application systems such as adhesives is improved, the system viscosity is reduced, and the addition amount of fillers in the pouring sealant can be increased.

The silane coupling agent includes but is not limited to at least one of methyltrimethoxysilane, triethoxysilane, vinyltrimethoxysilane, triethoxysilane, aminosilane, phenylaminosilane, epoxysilane, acryloxysilane.

Because the porous amorphous silicon dioxide powder has a porous structure and interpenetrated pore channels, the macromolecule of the pouring sealant can not only form hydrogen bonds with the surface of the powder, but also can be interconnected through the pore channels to form a more stable network structure, compared with the conventional anti-settling agent, the anti-settling porous amorphous silicon dioxide powder has the effect of preventing the heat-conducting powder from settling with less addition amount, and has less influence on the overall heat-conducting performance of the heat-conducting pouring sealant; as the porous amorphous silicon dioxide powder is micron-sized, compared with the conventional nanoscale anti-settling agent, the porous amorphous silicon dioxide powder has the advantages that the network nodes formed in the pouring sealant with the same addition amount are less, and the influence on the leveling property of the pouring sealant system is small.

The porous amorphous silica powder can be used as an anti-settling agent of the water-based or solvent-based coating.

The invention has the beneficial effects that: the invention prepares a porous amorphous silicon dioxide powder, which has a porous structure and interpenetrated pore channels; the powder is used as an anti-settling agent in pouring sealant, and the macromolecules of the pouring sealant can be interconnected through a pore channel to form a stable network structure; and the powder can be added in a small amount to prevent the heat-conducting powder from precipitating, and the influence on the overall heat-conducting performance and the leveling property of the heat-conducting pouring sealant is small.

The attached drawings of the specification:

FIG. 1 is a schematic structural view of a porous amorphous silica powder according to the present invention;

wherein, 1-nano silicon dioxide; 2-a pore channel;

FIG. 2 is a scanning electron micrograph of the porous amorphous silica powder prepared in example 2.

The specific implementation mode is as follows:

in order to make the technical means, the original characteristics, the achieved purposes and the effects of the invention easy to understand, the invention is further explained by combining the specific embodiments and the drawings.

The raw materials adopted by the invention are as follows:

vinyl silicone oil: viscosity 150cs, supplied by organosilicon Limited liability company of Xinanmai chart of Zhejiang;

two-component organic silicon gel: the model R-6509 mainly comprises vinyl-terminated silicone oil, and the two components are respectively as follows: the component R-6509A contains a cross-linking agent with the viscosity of 250-350 mPa.s; the component R-6509B contains a catalyst of 200-300mPa.s, which is provided by Guangdong standard Mei silicon fluoride new material Co.Ltd;

heat-conducting filler: spherical alumina heat-conducting powder, model XY-25, provided by Anhui Shitong materials science and technology Co., Ltd;

nano silicon dioxide: the average particle size is 5-50nm, provided by Wingchuang Texaco.

Precipitation method white carbon black: the specific surface area is 167m²/g。