阅读说明：本技术 一种高分散低密度纳米二氧化硅的粘胶分散制备方法 (Viscose dispersion preparation method of high-dispersion low-density nano silicon dioxide ) 是由 金鑫 吕子剑 王朝兵 于 2020-06-09 设计创作，主要内容包括：本发明公开了一种高分散低密度纳米二氧化硅的粘胶分散制备方法。该方法以水玻璃为原料,利用生物纤维材料制备得到的粘胶作为水玻璃的分散体系,将形成的粘胶纤维-原硅酸分散体系通过微孔挤出至硫酸介质中固化,形成的硅胶由再生纤维包覆而分散；将该含硅粘胶再生纤维材料在空气中高温煅烧,硅胶转化为二氧化硅微粒,而纤维质物质则被高温分解,燃烧转化为二氧化碳除去,最终形成高分散性纳米二氧化硅材料。本发明制得的二氧化硅材料具有比表面积大,相对密度小,粒径小且粒径分布窄等特点。而且本发明的制备方法简单,原料价廉易得,设备要求简单,用水量少,污染小。(The invention discloses a method for preparing high-dispersion low-density nano silicon dioxide by viscose dispersion. The method takes water glass as a raw material, utilizes viscose prepared from a biological fiber material as a dispersion system of the water glass, extrudes the formed viscose fiber-orthosilicic acid dispersion system into a sulfuric acid medium through micropores for curing, and forms silica gel which is coated by regenerated fibers and dispersed; the silicon-containing viscose regenerated fiber material is calcined in the air at high temperature, silica gel is converted into silica particles, and cellulosic substances are decomposed at high temperature and are burnt to be converted into carbon dioxide to be removed, so that the high-dispersity nano silica material is finally formed. The silicon dioxide material prepared by the invention has the characteristics of large specific surface area, small relative density, small particle size, narrow particle size distribution and the like. The preparation method is simple, the raw materials are cheap and easy to obtain, the equipment requirement is simple, the water consumption is low, and the pollution is low.)

1. A viscose dispersion preparation method of high-dispersion low-density nano silicon dioxide is characterized by comprising the following specific steps:

(1) adding water glass and a dispersing agent into the viscose solution, stirring uniformly to form silicon-containing viscose, and standing and curing;

(2) injecting the silicon-containing viscose into a sulfuric acid coagulation bath through a micropore nozzle for solidification to form silicon-containing viscose regenerated fibers, washing the regenerated fibers with water to be neutral, and drying the regenerated fibers;

(4) and (3) calcining the dried silicon-containing viscose regenerated fibers at high temperature, and converting carbon-containing cellulose substances into carbon dioxide to remove the carbon dioxide to obtain the high-dispersion low-density nano silicon dioxide.

2. The method according to claim 1, wherein SiO is contained in the water glass₂The content of the sodium silicate is 25-35 percent, and the modulus of the water glass is 2.0-4.5; the mass ratio of the viscose solution to the water glass is 0.5:1-3: 1.

3. The method of claim 1, wherein the dispersant is a fatty acid or a soluble salt of a fatty acid.

4. The method according to claim 1, wherein the dispersant is one or more selected from stearic acid and its soluble salt, n-octanoic acid, n-hexanoic acid, sodium dodecyl sulfonate, and polyacrylic acid.

5. The preparation method according to claim 1, wherein the dispersant is added in an amount of 0.1 to 3% by mass based on the mass of the water glass.

6. The method according to claim 1, wherein the stirring in step (1) is carried out at a linear speed of 10 to 15 m-min^-1(ii) a The curing time is 1-4 hours.

7. The production method according to claim 1, wherein the concentration of sulfuric acid in the sulfuric acid coagulation bath is 1 to 6 mol-L^-1。

8. The method as claimed in claim 1, wherein the temperature of the high-temperature calcination is 800-1000 ℃.

9. The method according to claim 1, wherein the viscose solution is prepared by: taking a biomass material containing cellulose as a raw material, crushing, adding into alkali liquor, boiling for 1-5h, cooling to room temperature, filtering out the cellulose material in the alkali liquor, squeezing water, and drying; mixing the dried alkalized cellulosic material with CS₂Mixing, stirring uniformly, adding alkali solution, and stirring to completely dissolve cellulose into orange viscose solution.

10. The method for preparing the biomass material as claimed in claim 9, wherein the cellulose-containing biomass material is selected from one or more of cotton, bagasse, reed, straw, bamboo and straw.

The technical field is as follows:

the invention belongs to the technical field of nano-silica preparation, and particularly relates to a viscose dispersion preparation method of high-dispersion low-density nano-silica.

Background art:

the inorganic filler plays an important role in the material by the unique physical and chemical properties, can generally toughen and reinforce a single matrix material, improves the aging resistance, corrosion resistance and other capabilities of a product, and can greatly reduce the cost of the product. It is considered that the smaller the particle size of the inorganic filler is, the more prominent the effect of the filler is. Therefore, the powder technology of inorganic fillers has been rapidly developed in recent decades. At present, the production of ultrafine and even nanoscale inorganic powders has become a hot spot.

The ultrafine silicon dioxide, commonly called white carbon black, is one of inorganic fillers, and is widely applied to products in various industries such as catalyst carriers, high-molecular composite materials, electronic packaging materials, precise ceramic materials, rubber, papermaking, plastics, glass steel, adhesives, high-grade fillers, sealants, coatings, optical fibers, precise casting and the like due to the high purity, low density, high specific surface area, good dispersibility, hydrogen bonds with different strengths formed by surface silanol groups and active silane bonds, and excellent optical properties and mechanical properties. The importance of precipitated silica in the synthesis of silica is the forefront, and in particular, in recent years, precipitated silica has increasingly wide application in the fields of military affairs, communication, electronics, laser technology, biology and the like.

China is a large world for producing silicon dioxide at present, but the production capacity of high-quality nano silicon dioxide is far less than the market consumption, the demand of high-quality silicon dioxide is greatly increased by the high-tech products such as cathode electrophoretic paint, finish paint, large-scale integrated circuit sealing agent, high-grade powder coating and the like in the automobile industry along with the increase of the demand of organic silicon sealant in the building industry, the automobile industry, the electrical industry and the like by import.

One of the important problems to be faced in the production of ultrafine powder materials is the agglomeration of ultrafine particles. For a powder particle, when the particle size is reduced to a certain degree, the specific surface area of the powder material will increase rapidly, and the number of atoms occupying the surface of the particle will increase more greatly than that of the product of the large particle, thereby causing imbalance of the surface charge of the particle and causing rapid rise of the surface energy of the particle. The nanometer particles have small particle size and high surface energy, are seriously prone to mutually conglomerate to reduce the surface energy, show that the nanometer particles are easy to agglomerate to form secondary particles, further cause the instability and the easy aggregation of nanometer-sized materials, and ensure that the nanometer particles cannot show unique surface area effect, volume effect, quantum size effect and the like. In order to reduce the surface energy of the particles, the powder particles have a tendency of being adhered and aggregated with each other to reduce the surface atomic number so as to reduce the surface charge and the surface potential, thereby forming crystals with larger particle size, reducing the surface energy of the particles and improving the stability, and the influence factors finally cause the product to lose a series of excellent properties of the superfine material. The agglomeration of particles is generally divided into two categories: soft agglomeration and hard agglomeration. Soft agglomeration is mainly due to van der waals and coulomb forces between particles, and the agglomeration can be eliminated by some chemical or mechanical energy method. In addition to van der waals and coulomb forces between particles, there is also a chemical bond effect within the hard aggregate of particles. At present, the typical theories for explaining the formation of the hard agglomerates include a crystal bridge theory, a hydrogen bond or chemical bond action theory and a capillary adsorption theory. When the liquid phase method is used for preparing the nano powder, the reaction agglomeration is carried out in two steps: as a first step, the prevention of agglomeration of particles during gelling, i.e. the formation of secondary particles from primary particles, is currently less investigated in this respect. Second, prior to the drying process, a number of methods have been used to control the secondary agglomeration of the gel, and much work has been done in this regard. Among these methods, the method of eliminating hard agglomeration by modifying the surface of nano powder with a surfactant is currently the most economical and widely used method.

When the silicon dioxide is prepared by a precipitation method, the initial precipitation form is the ortho-silicic acid, and the surface of the ortho-silicic acid precipitation is rich in hydroxyl, so that the hydroxyl hydrogen bond among silicic acid particles is very strong, and the agglomeration is very easy to form. For this reason, the silica products prepared by the reaction of water glass and sulfuric acid have a primary particle size of 50nm, but the final product has a particle size of more than 20 μm due to the presence of agglomeration. Therefore, in order to prevent the agglomeration of nanoparticles and improve the dispersibility and durability of nanoparticles and reduce the particle size of products, it is necessary to perform surface treatment and modification on the nanoparticles in the synthesis of ultrafine silica in view of the instability of the nanoparticles. Prevent the hydroxyl groups from agglomerating and forming oxygen bridges after dehydroxylation, resulting in non-dispersible hard agglomerates. Therefore, in the process of preparing the nano silicon dioxide by the precipitation method, the prevention of the agglomeration of product particles is the most key problem of improving the product quality and expanding the application range of products, is the requirement of modern science, industry and technology, and has great research and application significance.

The invention content is as follows:

the invention aims to provide a viscose dispersion preparation method of high-dispersion low-density nano silicon dioxide. The method takes water glass as a raw material, utilizes viscose prepared from a biological fiber material as a dispersion system of the water glass, and disperses the water glass into the viscose to form a uniform dispersion viscose system of the water glass coated by the viscose; extruding the viscose fiber-orthosilicic acid dispersion system into a sulfuric acid medium through micropores for curing, acidifying water glass by sulfuric acid to form silica gel, curing the viscose fiber by sulfuric acid to form regenerated fiber, and coating the silica gel by the regenerated fiber for dispersing; the silicon-containing viscose regenerated fiber material is calcined at high temperature in the air, silica gel is converted into silica particles, and cellulosic substances are decomposed at high temperature and are burnt to be converted into carbon dioxide to be removed, and finally the high-dispersity nano silica material is formed. The silicon dioxide material has the characteristics of large specific surface area, small relative density, small particle size, narrow particle size distribution and the like.

The viscose dispersion preparation method of the high-dispersion low-density nano silicon dioxide comprises the following steps:

(1) adding water glass and a dispersing agent into the viscose solution, stirring uniformly to form silicon-containing viscose, and standing and curing;

(2) injecting the silicon-containing viscose into a sulfuric acid coagulation bath through a micropore nozzle for solidification to form silicon-containing viscose regenerated fibers, washing the regenerated fibers with water to be neutral, and drying the regenerated fibers;

(4) and (3) calcining the dried silicon-containing viscose regenerated fibers at high temperature, and converting carbon-containing cellulose substances into carbon dioxide to remove the carbon dioxide to obtain the high-dispersion low-density nano silicon dioxide.

SiO in the water glass₂The content of (A) is 25-35%, and the modulus of water glass (ratio of silicon oxide to sodium oxide) is 2.0-4.5.

The dispersant is fatty acid or soluble salt of the fatty acid.

The dispersant is selected from one or more of stearic acid and soluble salt thereof, n-octanoic acid, n-hexanoic acid, sodium dodecyl sulfate and polyacrylic acid. The molecular weight of the polyacrylic acid is 2000-6000.

The mass ratio of the viscose solution to the water glass is 0.5:1-3: 1.

The addition amount of the dispersant is 0.1-3% of the mass of the water glass.

The linear velocity of the paddle for stirring in the step (1) is 10-15 m.min^-1。

The curing time is 1-4 hours.

The concentration of the sulfuric acid in the sulfuric acid coagulation bath is 1-6 mol.L^-1。

The temperature of the high-temperature calcination is 800-1000 ℃.

The preparation method of the viscose solution comprises the following steps: taking a biomass material containing cellulose as a raw material, crushing, adding into alkali liquor, boiling for 1-5h, cooling to room temperature, filtering out the cellulose material in the alkali liquor, squeezing water, and drying; mixing the dried alkalized cellulosic material with CS₂Mixing, stirring uniformly, adding alkali solution, and stirring to completely dissolve cellulose into orange viscose solution.

The cellulose-containing biomass material is selected from one or more of cotton, bagasse, reed, orange straw, bamboo and straw.

Compared with the traditional silicon dioxide material prepared by water glass through a precipitation method, the silicon dioxide material prepared by the method has the following characteristics: high specific surface area of about 300-600 m²·L^-1(ii) a The apparent density is small and is 0.05 to 0.07 g/mL^-1To (c) to (d); the average particle size is small, about 60 to 80 nm. And has the advantages of narrow particle size distributionThe invention has the following advantages:

(1) the invention selects the viscose fiber coating method treatment process to coat the orthosilicic acid precipitated by the water glass through sulfuric acid, thereby preventing the dehydration process among hydroxyl groups on the surfaces of different particles when the orthosilicic acid is heated and dehydrated to form silicon dioxide, and further preventing the occurrence of hard agglomeration caused by the formation of oxygen bridges among particles. The method has simple treatment process and is convenient to apply to industrial production.

(2) The raw materials used in the invention are simple and easy to obtain, and can meet the requirement of large-scale production.

(3) Compared with the traditional production process of silicon dioxide by a precipitation method, the method reduces a large amount of washing water, reduces the discharge of waste water and lightens the environmental pressure. Compared with the production of silicon dioxide by a gas phase method, the method has the advantages of simple equipment requirement, low cost and little pollution.

Description of the drawings:

FIG. 1 is an electron micrograph of the nanosilica prepared in example 5.

Fig. 2 is a volume particle size distribution diagram of nano-silica prepared in example 5.

The specific implementation mode is as follows:

the invention is explained in detail below with reference to laboratory examples. The viscose solution used is prepared from cotton, and the preparation method of the viscose solution comprises the following steps: taking cotton as a raw material, and crushing the cotton according to the following fiber amount: 1 part of alkali liquor: 10, adding the mixture into NaOH solution with the mass fraction of 18%, boiling for 2 hours, cooling to room temperature, filtering out cellulose materials in alkali liquor, squeezing out water, and drying at 105 ℃; drying the alkalized cellulose material according to the mass ratio of 1: 1 and CS₂Mixing, stirring uniformly, adding 5% NaOH which is 5 times of the mass of the alkalized cellulose, and stirring for 2h to completely dissolve the cellulose into an orange viscose solution, wherein the concentration of the orange viscose solution is 20g per 100mL of viscose solution.

Example 1:

(1) taking 100mL of viscose solution, adding SiO₂100mL of 25 wt% water glass with the modulus of 4.1 is stirred at a high speed for 15min, 0.25g of dispersant sodium stearate is added, the mixture is stirred uniformly to prepare the silicon-containing viscose glue, and the silicon-containing viscose glue is placed and cured for 2h at the temperature of 60 ℃;

(2) injecting the silicon-containing viscose glue into a micropore sprayer by 2 mol.L^-1Sulfuric acid (D) ofIn the step (2), preparing the silicon-containing viscose regenerated fiber;

(3) washing the silicon-containing viscose regenerated fiber in water to be neutral, and drying in an oven at 60 ℃;

(4) and calcining the dried silicon-containing viscose regenerated fiber in a muffle furnace at 850 ℃ for 2h to convert fiber substances into carbon dioxide to be removed, thereby obtaining the high-dispersity nano silicon dioxide product.

The volume average particle diameter of the prepared silicon dioxide product is 65nm through detection, and the apparent density is 0.057g cm^-3Specific surface area 450m²·g^-1。

Example 2:

(1) 80mL of viscose solution was taken and added with SiO₂150mL of water glass with the content of 32 wt% and the modulus of 2.8 is stirred at a high speed for 15min, 1g of dispersing agent sodium n-octoate is added, the mixture is stirred uniformly to prepare the silicon-containing viscose, and the silicon-containing viscose is placed and cured for 4h at the temperature of 80 ℃;

(2) injecting the silicon-containing viscose glue into a micropore sprayer by 2 mol.L^-1Preparing the silicon-containing viscose regenerated fiber in the sulfuric acid;

(3) washing the silicon-containing viscose regenerated fiber in water to be neutral, and drying in an oven at 80 ℃;

(4) and calcining the dried silicon-containing viscose regenerated fiber in a muffle furnace at 1000 ℃ for 2h to convert fiber substances into carbon dioxide for removal, thereby obtaining the high-dispersity nano silicon dioxide product.

The volume average particle diameter of the prepared silicon dioxide product is 82nm through detection, and the apparent density is 0.072g cm^-3Specific surface area 320m²·g^-1。

Example 3:

(1) taking 100mL of viscose solution, adding SiO₂120mL of water glass with the content of 32 wt% and the modulus of 3.5 is stirred at a high speed for 15min, 0.5g of dispersant sodium dodecyl sulfate is added, the mixture is stirred uniformly to prepare the silicon-containing viscose glue, and the silicon-containing viscose glue is placed and cured for 1h at the temperature of 60 ℃;

(2) injecting the silicon-containing viscose glue into a micropore sprayer by 2 mol.L^-1Preparing the silicon-containing viscose regenerated fiber in the sulfuric acid;

(3) washing the silicon-containing viscose regenerated fiber in water to be neutral, and drying in an oven at 80 ℃;

(4) and calcining the dried silicon-containing viscose regenerated fiber in a muffle furnace at 800 ℃ for 4h to convert fiber substances into carbon dioxide for removal, thereby obtaining the high-dispersity nano silicon dioxide product.

The volume average particle diameter of the prepared silicon dioxide product is 70nm through detection, and the apparent density is 0.068g cm^-3Specific surface area of 350m²·g^-1。

Example 4:

(1) taking 100mL of viscose solution, adding SiO₂30mL of 30 wt% water glass with the modulus of 3.0, stirring at a high speed for 15min, adding 0.3g of dispersant polyacrylic acid, stirring uniformly to prepare the silicon-containing viscose, and standing and curing for 2h at 70 ℃;

(2) injecting the silicon-containing viscose glue into a micropore sprayer by 2 mol.L^-1Preparing the silicon-containing viscose regenerated fiber in the sulfuric acid;

(3) washing the silicon-containing viscose regenerated fiber in water to be neutral, and drying in an oven at 80 ℃;

(4) and calcining the dried silicon-containing viscose regenerated fiber in a muffle furnace at 850 ℃ for 3h to convert fiber substances into carbon dioxide to be removed, thereby obtaining the high-dispersity nano silicon dioxide product.

The volume average particle diameter of the prepared silicon dioxide product is 60nm through detection, and the apparent density is 0.052g cm^-3Specific surface area of 570m²·g^-1。

Example 5:

(1) taking 100mL of viscose solution, adding SiO₂150mL of 30 wt% water glass with the modulus of 4.18, stirring at a high speed for 15min, adding 0.5g of dispersant polyacrylic acid, stirring uniformly to prepare the silicon-containing viscose, and standing and curing for 2h at the temperature of 60 ℃;

(2) injecting the silicon-containing viscose glue into a micropore sprayer by 2 mol.L^-1Preparing the silicon-containing viscose regenerated fiber in the sulfuric acid;

(3) washing the silicon-containing viscose regenerated fiber in water to be neutral, and drying in an oven at 60 ℃;

(4) and calcining the dried silicon-containing viscose regenerated fiber in a muffle furnace at 900 ℃ for 2h to convert fiber substances into carbon dioxide for removal, thereby obtaining the high-dispersity nano silicon dioxide product.

The volume average particle diameter of the prepared silicon dioxide product is 75nm through detection, and the apparent density is 0.065g cm^-3Specific surface area 380m²·g^-1。