阅读说明：本技术 纳米二氧化硅的制备方法及表面改性方法 (Preparation method and surface modification method of nano silicon dioxide ) 是由 杨威 严顺洪 肖立鲜 陈敏 黎超 于 2020-05-22 设计创作，主要内容包括：本发明属于纳米材料技术领域,特别涉及纳米二氧化硅的制备方法及表面改性方法。制备方法包括以下步骤：向含有水和氨的醇类物质中加入正硅酸乙酯得到反应体系,反应体系进行反应,得到含有纳米二氧化硅的分散液。本发明制备方法通过调整水浓度、氨浓度和/或反应温度等,能够得到不同粒径的纳米二氧化硅。表面改性方法包括以下步骤：纳米二氧化硅分散液中加入甲基丙烯酰氧丙基三甲氧基硅烷,常温下反应,然后升温继续反应,得到改性的纳米二氧化硅分散液。本发明改性方法能够对纳米二氧化硅进行改性,具有良好的效果。(The invention belongs to the technical field of nano materials, and particularly relates to a preparation method and a surface modification method of nano silicon dioxide. The preparation method comprises the following steps: adding ethyl orthosilicate into alcohol substances containing water and ammonia to obtain a reaction system, and reacting the reaction system to obtain dispersion liquid containing nano silicon dioxide. The preparation method can obtain the nano silicon dioxide with different particle sizes by adjusting the water concentration, the ammonia concentration, the reaction temperature and/or the like. The surface modification method comprises the following steps: adding methacryloxypropyl trimethoxy silane into the nano silicon dioxide dispersion liquid, reacting at normal temperature, and then heating to continue the reaction to obtain the modified nano silicon dioxide dispersion liquid. The modification method can modify the nano silicon dioxide and has good effect.)

1. The preparation method of the nano silicon dioxide is characterized by comprising the following steps of adding ethyl orthosilicate into alcohol substances containing water and ammonia to obtain a reaction system, reacting the reaction system at the temperature of 22-40 ℃ to obtain dispersion liquid containing the nano silicon dioxide, wherein the ammonia concentration of the reaction system is 0.1-7.5 mol/L, and the water concentration is 0.05-15 mol/L.

2. The method for preparing nano silica according to claim 1, characterized in that: the alcohol substance is at least one of ethanol, methanol or isopropanol.

3. The method for preparing nano silica according to claim 1 or 2, characterized in that: dispersing the ethyl orthosilicate in an alcohol substance, and then adding the ethyl orthosilicate into the alcohol substance containing water and ammonia; further, the addition is completed within 10-20 min.

4. The method for preparing nano silicon dioxide according to any one of claims 1 to 3, wherein the concentration of tetraethoxysilane in the reaction system is 0.3 to 0.7 mol/L.

5. The method for preparing nano silica according to any one of claims 1 to 4, characterized in that:

when the reaction temperature is 25 +/-3 ℃, and when the water concentration in the reaction system is 0.05-2.5 mol/L, the ammonia concentration is 0.1-0.5 mol/L, and the ethyl orthosilicate concentration is 0.1-0.3 mol/L, preparing nano silicon dioxide with the particle size of 30-100 nm;

when the reaction temperature is 25 +/-3 ℃, and when the water concentration in the reaction system is 2.6-6 mol/L, the ammonia concentration is 0.55-1.6 mol/L, and the ethyl orthosilicate concentration is 0.2-0.45 mol/L, preparing nano silicon dioxide with the particle size of 100-200 nm;

when the reaction temperature is 25 +/-3 ℃, and when the water concentration in the reaction system is 6-8 mol/L, the ammonia concentration is 1.7-2.5 mol/L, and the ethyl orthosilicate concentration is 0.3-0.65 mol/L, preparing nano silicon dioxide with the particle size of 200-300 nm;

when the reaction temperature is 25 +/-3 ℃, and when the water concentration in the reaction system is 8-12 mol/L, the ammonia concentration is 1.8-4.5 mol/L, and the ethyl orthosilicate concentration is 0.32-0.75 mol/L, preparing nano silicon dioxide with the particle size of 300-400 nm;

when the reaction temperature is 25 +/-3 ℃, and when the water concentration in the reaction system is 12-15 mol/L, the ammonia concentration is 5-7.5 mol/L, and the ethyl orthosilicate concentration is 0.36-0.9 mol/L, preparing nano silicon dioxide with the particle size of 400-500 nm;

further, when the reaction temperature is 25 ℃, when NH is contained in the reaction system₃The concentration is 0.1 mol/LReacting for 24 hours to obtain nano silicon dioxide with the particle size of 35nm, wherein the water concentration is 0.1 mol/L, and the tetraethoxysilane concentration is 0.15 mol/L;

when the reaction temperature is 25 ℃, when NH is contained in the reaction system₃The concentration is 0.56 mol/L, the water concentration is 5 mol/L, the concentration of tetraethoxysilane is 0.3 mol/L, and the reaction is carried out for 24 hours to obtain nano silicon dioxide with the particle size of 180 nm;

when the reaction temperature is 25 ℃, when NH is contained in the reaction system₃The concentration is 1.8 mol/L, the water concentration is 6 mol/L, the concentration of tetraethoxysilane is 0.35 mol/L, and the reaction is carried out for 24 hours to obtain nano silicon dioxide with the particle size of 220 nm;

when the reaction temperature is 25 ℃, when NH is contained in the reaction system₃The concentration is 2.1 mol/L, the water concentration is 8 mol/L, the concentration of tetraethoxysilane is 0.4 mol/L, and the reaction is carried out for 24 hours to obtain the nano silicon dioxide with the particle size of 330 nm;

when the reaction temperature is 25 ℃, when NH is contained in the reaction system₃The concentration is 6 mol/L, the water concentration is 13 mol/L, the concentration of the ethyl orthosilicate is 0.5 mol/L, and the nano silicon dioxide with the particle size of 460nm is obtained after 24 hours of reaction.

6. The surface modification method of the nano silicon dioxide is characterized by comprising the following steps: the method comprises the following steps: adding methacryloxypropyl trimethoxysilane into the dispersion liquid containing the nano-silica, reacting at normal temperature, and then heating to 2-5 ℃ lower than the boiling point of the solvent for continuous reaction to obtain the modified nano-silica dispersion liquid.

7. The method of claim 6, wherein the surface modification of the nanosilica is carried out by: the dispersion liquid containing nano-silica is the dispersion liquid containing nano-silica prepared by the method of any one of claims 1 to 5, the dispersion liquid containing nano-silica prepared by other methods, or the dispersion liquid formed by dispersing solid nano-silica in alcohol substances.

8. The method for surface modification of nanosilica as claimed in claim 6 or 7, characterized in that: when the modification is chemical modification, the particle size of the modified nano-silica is below 80 nm.

9. The method for modifying the surface of nanosilica as claimed in any one of claims 6 to 8, wherein: the normal temperature is 22-28 ℃; reacting for 10-15 h at normal temperature; the continuous reaction time is 50 min-1.5 h.

10. The method for modifying the surface of nanosilica as claimed in any one of claims 6 to 9, wherein: each 1gSiO₂Correspondingly adding 0.1-1 g of methacryloxypropyltrimethoxysilane; further, each 1gSiO₂Corresponding to 0.3g of methacryloxypropyltrimethoxysilane.

Technical Field

The invention belongs to the technical field of nano materials and polymer composite materials, and particularly relates to a preparation method and a surface modification method of nano silicon dioxide.

Background

The nano silicon dioxide is a material which is widely applied in the fields of coatings, adhesives, concrete, textile, medicine and the like. Because the nano silicon dioxide belongs to inorganic nano materials, the specific surface area is large, the nano silicon dioxide is difficult to disperse, and when the nano silicon dioxide is compounded with materials with different physical and chemical properties for use, the nano silicon dioxide is often applied after being chemically modified.

At present, the method for preparing the nano silicon dioxide mainly comprises a dry method and a wet method, wherein the dry method is mainly used for preparing the silicon dioxide nano material in the industrial production, and the wet method is mainly used for preparing the silicon dioxide by adopting the hydrolysis mode of a precursor. Problem of preparing nano silicon dioxide by industrial gas phase method and powdery nano SiO prepared by gas phase method₂It is industrialized, but the monodispersity and morphology of the particle size cannot be controlled. The sol-gel method is to prepare nano SiO by hydrolytic condensation reaction of silicate ester (such as TEOS)₂Has become to prepare monodisperse nano SiO₂The main method of (1). For example, the literature:

CN 103626188A silicon dioxide particles and a preparation method thereof, nanometer silicon dioxide with the particle size of 5-500nm is prepared by tetraalkoxysilane in an alkaline catalyst solution.

CN 104114627A organosilicon compound grafted silicon dioxide preparation method, describe that organosilicon compound is used to carry on the chemical modification to the surface of nanometer silicon dioxide, nanometer silicon dioxide grafted through organosilicon compound can be used in the silicone elastomer, strengthen the well-known color breaking strength and tensile strength of the silicone elastomer.

CN 106040162B is a surface modified silicon dioxide material and a preparation method thereof, introduces that nano silicon dioxide is modified by trimethoxy silane in ethanol, and reports that the modified nano silicon dioxide has a selective adsorption function on silver ions.

CN 110240168A is a preparation method of small-size modified nano-silica, which describes that after a polymer with positive charges is mixed with an organic solvent, an organic silicon precursor is added and mixed, and after hydrolysis reaction, the silica with the particle size of 15-25nm of the surface graft polymer is obtained.

Disclosure of Invention

The first technical problem to be solved by the invention is to provide a preparation method of nano silicon dioxide, which comprises the following steps of adding ethyl orthosilicate into an alcohol substance containing water and ammonia to obtain a reaction system, and reacting the reaction system at 22-40 ℃ to obtain a dispersion liquid containing the nano silicon dioxide, wherein the ammonia concentration in the reaction system is 0.1-7.5 mol/L, and the water concentration is 0.05-15 mol/L.

Further, the method for producing nano-silica may further comprise removing a liquid in the dispersion containing nano-silica to obtain solid nano-silica particles.

Specifically, in the preparation method of the nano-silica, the alcohol substance is at least one of ethanol, methanol or isopropanol.

Preferably, in the method for preparing nano-silica, the tetraethoxysilane is dispersed in an alcohol substance and then added to the alcohol substance containing water and ammonia. The alcohol substance is at least one of ethanol, methanol or isopropanol.

Further, in the preparation method of the nano silicon dioxide, the addition is completed within 10-20 min.

Preferably, in the preparation method of the nano silicon dioxide, the concentration of the ethyl orthosilicate in the reaction system is 0.3-0.7 mol/L.

Specifically, in the preparation method of the nano silicon dioxide, the reaction time is 16-24 hours.

Further, in the preparation method of the nano-silicon dioxide, when the reaction temperature is 25 +/-3 ℃, and when the water concentration in the reaction system is 0.05-2.5 mol/L, the ammonia concentration is 0.1-0.5 mol/L, and the ethyl orthosilicate concentration is 0.1-0.3 mol/L, the nano-silicon dioxide with the particle size of 30-100 nm is prepared.

Further, in the preparation method of the nano silicon dioxide, when the reaction temperature is 25 +/-3 ℃, and when the water concentration in the reaction system is 2.6-6 mol/L, the ammonia concentration is 0.55-1.6 mol/L, and the ethyl orthosilicate concentration is 0.2-0.45 mol/L, the nano silicon dioxide with the particle size of 100-200nm is prepared.

Further, in the preparation method of the nano-silicon dioxide, when the reaction temperature is 25 +/-3 ℃, and when the water concentration in the reaction system is 6-8 mol/L, the ammonia concentration is 1.7-2.5 mol/L, and the ethyl orthosilicate concentration is 0.3-0.65 mol/L, the nano-silicon dioxide with the particle size of 200-300 nm is prepared.

Further, in the preparation method of the nano-silicon dioxide, when the reaction temperature is 25 +/-3 ℃, and when the water concentration in the reaction system is 8-12 mol/L, the ammonia concentration is 1.8-4.5 mol/L, and the ethyl orthosilicate concentration is 0.32-0.75 mol/L, the nano-silicon dioxide with the particle size of 300-400 nm is prepared.

Further, in the preparation method of the nano-silicon dioxide, when the reaction temperature is 25 +/-3 ℃, and when the water concentration in the reaction system is 12-15 mol/L, the ammonia concentration is 5-7.5 mol/L, and the ethyl orthosilicate concentration is 0.36-0.9 mol/L, the nano-silicon dioxide with the particle size of 400-500 nm is prepared.

Furthermore, in the preparation method of the nano silicon dioxide, whenThe reaction temperature is 25 ℃, when NH is in the reaction system₃The concentration is 0.1 mol/L, the water concentration is 0.1 mol/L, the concentration of the ethyl orthosilicate is 0.15 mol/L, and the nano silicon dioxide with the particle size of 35nm is obtained after 24 hours of reaction.

Furthermore, in the preparation method of the nano silicon dioxide, when the reaction temperature is 25 ℃, when NH is in the reaction system₃The concentration is 0.56 mol/L, the water concentration is 5 mol/L, the concentration of the tetraethoxysilane is 0.3 mol/L, and the nano silicon dioxide with the particle size of 180nm is obtained after 24 hours of reaction.

Furthermore, in the preparation method of the nano silicon dioxide, when the reaction temperature is 25 ℃, when NH is in the reaction system₃The concentration is 1.8 mol/L, the water concentration is 6 mol/L, the concentration of tetraethoxysilane is 0.35 mol/L, and the nano silicon dioxide with the particle size of 220nm is obtained after 24 hours of reaction.

Furthermore, in the preparation method of the nano silicon dioxide, when the reaction temperature is 25 ℃, when NH is in the reaction system₃The concentration is 2.1 mol/L, the water concentration is 8 mol/L, the concentration of the tetraethoxysilane is 0.4 mol/L, and the nano silicon dioxide with the particle size of 330nm is obtained after 24 hours of reaction.

Furthermore, in the preparation method of the nano silicon dioxide, when the reaction temperature is 25 ℃, when NH is in the reaction system₃The concentration is 6 mol/L, the water concentration is 13 mol/L, the concentration of the ethyl orthosilicate is 0.5 mol/L, and the nano silicon dioxide with the particle size of 460nm is obtained after 24 hours of reaction.

The second technical problem to be solved by the invention is to provide a surface modification method of nano silicon dioxide. The method comprises the following steps: adding Methacryloxypropyltrimethoxysilane (MPS) into the dispersion liquid containing the nano-silica, reacting at normal temperature, and then heating to 2-5 ℃ lower than the boiling point of the solvent for further reaction to obtain the modified nano-silica dispersion liquid.

Further, the method for modifying the surface of the nano-silica further comprises the steps of cooling the modified nano-silica dispersion, separating, washing, drying and grinding to obtain the modified nano-silica solid.

Further, in the method for modifying the surface of nanosilica, when the modification is chemical modification, the particle diameter of the modified raw nanosilica is 80nm or less.

Specifically, in the method for modifying the surface of nanosilica, the nanosilica-containing dispersion is a nanosilica-containing dispersion prepared by the above method, a nanosilica-containing dispersion prepared by another method, or a dispersion in which solid nanosilica particles are dispersed in an alcohol. The alcohol substance is at least one of ethanol, methanol or isopropanol. The water content of the alcohol substance is below 3%.

Specifically, in the surface modification method of the nano-silica, the normal temperature is 22-28 ℃. And reacting for 10-15 h at normal temperature.

Specifically, in the surface modification method of the nano-silica, when the solvent in the dispersion liquid is ethanol, the continuous reaction temperature is 70-76 ℃.

Specifically, in the surface modification method of the nano-silica, the continuous reaction time is 50min to 1.5 h.

Specifically, in the surface modification method of the nano-silica, 1gSiO 2 is used₂Correspondingly adding 0.1-1 g of MPS.

Preferably, in the method for modifying the surface of nano-silica, 1gSiO 2 is used₂Corresponding to 0.3g of MPS.

Specifically, in the surface modification method of the nano silicon dioxide, the heating rate is 5-8 ℃/min.

The method for preparing the nano silicon dioxide has the advantages of easily available and cheap raw materials, simple and convenient reaction process operation, easily controlled reaction conditions, safe process, energy conservation and environmental protection; the nano silicon dioxide with different particle sizes can be obtained by controlling through adjusting the water concentration, the ammonia concentration and/or the reaction temperature of the reaction system, and the particle size of the nano silicon dioxide can be regulated and controlled only through adjusting the reaction temperature under the condition that the raw materials are not changed. The method can obtain the nano silicon dioxide with good monodispersity, and the nano silicon dioxide has uniform grain diameter and no agglomeration phenomenon. The dispersion liquid containing the nano silicon dioxide obtained by the method can be directly used for the subsequent surface modification of the nano silicon dioxide, the nano silicon dioxide particles do not need to be separated from the dispersion liquid, the continuous and uninterrupted operation can be realized, and the MPS is easily dissolved in the nano silicon dioxide dispersion liquid, thereby being beneficial to the chemical modification reaction between the MPS and the nano silicon dioxide.

The surface modification method of the nano silicon dioxide can carry out physical and/or chemical modification on the nano silicon dioxide, particularly can carry out chemical modification on the nano silicon dioxide with the particle size of below 80nm, can obtain the modified nano silicon dioxide with good dispersity and stability, thereby improving the compatibility between the nano silicon dioxide and polymers (rubber, paint and plastic), can be directly blended and doped in the polymers to enhance the mechanical property and the corrosion resistance of the polymers, can also be copolymerized with other chemical raw materials by a chemical means, can provide further chemical reaction due to functional groups which can be used for chemical reaction and can be used for preparing organic/inorganic composite materials.

Drawings

FIG. 1 shows the surface hydroxyl bonding state of nano-silica with different particle sizes;

FIG. 2 is an infrared spectrum of silica having different particle sizes before and after modification; wherein, (a)30nm is not modified, (b)30nm is modified, (c)80nm is modified, (d)100 nm is modified, (e)220nm is not modified, and (f)220nm is modified.

Detailed Description

The preparation method of the nano silicon dioxide comprises the following steps of adding ethyl orthosilicate into alcohol substances containing water and ammonia to obtain a reaction system, and reacting the reaction system at the temperature of 22-40 ℃ to obtain dispersion liquid containing the nano silicon dioxide, wherein the ammonia concentration of the reaction system is 0.1-7.5 mol/L, and the water concentration is 0.05-15 mol/L.

In the preparation method of the nano silicon dioxide, the main factors influencing the particle size are the concentration of catalyst ammonia, the concentration of water and the reaction temperature. In the preparation method of the nano silicon dioxide, the catalyst NH in the reaction system is controlled₃The concentration of (A) is 0.1-7.5 mol/L, the concentration of water is 0.05-15 mol/L, and the reaction is carried outThe temperature is 22-40 ℃, and then any one or at least one of the factors is adjusted within the range, so that the nano silicon dioxide with different particle diameters can be obtained. For example:

the first condition is as follows: the particle size is controlled by proportioning

Mixing ammonia water, water and ethanol at 25 deg.C, stirring to obtain NH₃The concentration is 0.1M, the concentration of water is 0.1M, the concentration of ethyl orthosilicate is 0.15M, and the nano silicon dioxide with the particle size of 35nm is obtained after 24 hours of reaction.

Mixing ammonia water, water and ethanol at 25 deg.C, stirring to obtain NH₃The concentration is 0.56M, the concentration of water is 5M, the concentration of ethyl orthosilicate is 0.3M, and the nano silicon dioxide with the particle size of 180nm is obtained after 24 hours of reaction.

Mixing ammonia water, water and ethanol at 25 deg.C, stirring to obtain NH₃The concentration is 1.8M, the concentration of water is 6M, the concentration of ethyl orthosilicate is 0.35M, and the nano silicon dioxide with the particle size of 220nm is obtained after 24 hours of reaction.

Mixing ammonia water, water and ethanol at 25 deg.C, stirring to obtain NH₃The concentration is 2.1M, the concentration of water is 8M, the concentration of ethyl orthosilicate is 0.4M, and the nano silicon dioxide with the particle size of 330nm is obtained after 24 hours of reaction.

Mixing ammonia water, water and ethanol at 25 deg.C, stirring to obtain NH₃The concentration is 6M, the concentration of water is 13M, the concentration of ethyl orthosilicate is 0.5M, and the nano silicon dioxide with the particle size of 460nm is obtained after 24 hours of reaction.

Case two: controlling particle size by temperature

Under the same conditions, when the reaction temperature is increased to 40 ℃, the nano silicon dioxide with the particle size of 180nm is obtained at normal temperature, and the particle size of the nano silicon dioxide is 120 nm.

Under the same conditions, the nano silicon dioxide with the particle size of 330nm is obtained at normal temperature, and the particle size of the nano silicon dioxide is 200nm when the reaction temperature is increased to 40 ℃.

Under the same conditions, when the reaction temperature is increased to 40 ℃, the nano silicon dioxide with the particle size of 460nm is obtained at normal temperature, and the particle size of the nano silicon dioxide is 310 nm.

The surface chemical modification method of the nano silicon dioxide comprises the following steps: adding methacryloxypropyl trimethoxysilane (MPS) into a dispersion liquid containing the nano-silica, reacting at normal temperature, heating to 2-5 ℃ below the boiling point of a solvent, continuing to react, cooling, separating a product, washing with ethanol, drying, and grinding to obtain modified nano-silica; wherein the particle size of the raw material nano silicon dioxide is below 80 nm.

In the surface modification method of the nano silicon dioxide, MPS is fully hydrolyzed at normal temperature in the first stage, and a functional group (-OH) generated by the hydrolysis of the MPS is fully contacted with the surface of the nano silicon dioxide; and in the second stage, the temperature is raised, so that MPS and-OH on the surface of the nano silicon dioxide are subjected to a grafting reaction, and the reaction is promoted at a high temperature. The reaction temperature in the first stage is too low, so that the reaction time is prolonged; the second stage reaction temperature is related to the boiling point of the solvent, and is generally selected to be controlled to be 2-5 ℃ below the boiling point of the solvent. For example, the boiling point of ethanol is 78 ℃, the reaction temperature cannot exceed the boiling point, and the reaction temperature is controlled to be 70-76 ℃.

Test example 1

The invention carries out infrared spectrum detection before and after the modification of the nano silicon dioxide with different particle sizes, and the infrared spectrum detection is shown in figure 2.

FIG. 2, a is the IR spectrum of unmodified 30nm silica, of 469cm^-1Is a bending vibration absorption peak of Si-O-Si of 800cm^-1And 1100cm^-1Respectively is the absorption peak of the asymmetric stretching vibration and the symmetric stretching vibration of Si-O-Si, and the absorption peak of the bending vibration of Si-OH appears at 945cm^-1，2980cm^-1The nearby absorption peak belongs to C-H stretching vibration, and the existence of the C-H absorption peak indicates that incompletely hydrolyzed-OC exists on the surface of the particle₂H₅At 3433cm^-1an-OH absorption peak appears in the vicinity.

As can be seen from a and e in FIG. 2, the-OH absorption peak width of a is narrower than that of e, and the presence of hydrogen bonds between-OH is responsible for broadening the absorption peak of the infrared spectrum. It can be seen that-OH on the surface of 30nm silica exists mainly in an isolated state, while-OH on the surface of 220nm nano silica exists mainly in a manner of hydrogen bonding (as shown in fig. 1).

In FIG. 2, b, c, d and f are nano SiO with different particle sizes₂Infrared spectrum modified by MPS. B shows that the infrared spectrum of the modified 30nm silicon dioxide is 1723cm^-1An absorption peak of C ═ O appeared, indicating successful grafting of MPS to the particle surface. As shown in C, when the nanoparticle size is 80nm, the modified particle also shows a C ═ O absorption peak in the infrared spectrum, indicating that MPS reacts with hydroxyl groups on the surface of 80nm silica. D shows that when the particle size is larger than 80nm, no absorption peak of C ═ O appears in the infrared spectrum after MPS modification, which indicates that MPS does not react with hydroxyl on the particle surface and can not generate effective chemical grafting on the large-particle-size nanoparticles. As the particle size increases, the number of hydroxyl groups on the particle surface increases, but the specific surface area of silica decreases, and the number (concentration) of Si — OH per surface unit area decreases. From this, it is found that, when silica is modified with MPS, MPS that can be grafted to the surface of nano silica depends on the Si — OH concentration per unit mass of the particle surface, and since the hydroxyl group concentration on the particle surface of 80nm or more is low and the hydroxyl groups mainly exist by hydrogen bonding, the reactivity of MPS with the nano silica having a large particle size is low, and it is difficult for MPS to modify the surface chemically.

In the following examples, the ammonia concentration was 25%.