Silica is a high-tech inorganic fine chemical product

Silica, also known as silica, scientific name precipitated hydrated silica. It is a high-tech inorganic fine chemical product whose main component is SiO2. The properties and carbon black are similar to the appearance of a white, highly dispersed amorphous or flocculent powder that is also processed into granules as a commercial product. Light weight, the relative density of the original particle size below 0.3μm is 2.319-2.653, the melting point is 1750 ℃, insoluble in water and most acids, and will become water-absorbing fine particles when absorbed with water in the air. Soluble in caustic soda and hydrofluoric acid. Other chemicals do not react, do not decompose at high temperatures, and do not burn. Chemically inert to substrates and active ingredients and additives, and has good compatibility with many active ingredients commonly used in vitamins, hormones, fluoride, antibiotics, enzymes and cosmetics. Has high electrical insulation. Due to its porosity and large specific surface area, it has a large dispersing ability in raw rubber and exhibits high reinforcing properties in rubber. The surface modification of hydrophobic silica is easily dissolved in oil, rubber and plastic as a reinforcing filler, which will significantly improve its mechanical strength and tear resistance index. Due to different manufacturing methods, the physical and chemical properties and microstructure of silica will be different, so the application fields and application effects are also different.

Silica is roughly divided into precipitated silica and fumed silica according to the production method.

Silica is a general term for white powdery X-ray amorphous silicic acid and silicate products, mainly referring to precipitated silica, fumed silica and ultrafine silica gel, also including powdered synthetic silicic acid Aluminum and calcium silicate, etc.

Silica is roughly divided into precipitation silica and fumed silica according to the production method. Fumed silica is a white amorphous flocculent translucent solid colloidal nanoparticle (particle size less than 100nm) under normal conditions, which is non-toxic and has a huge specific surface area. The fumed silica is all nano-silica, the product purity can reach 99%, and the particle size can reach 10~20nm, but the preparation process is complicated and expensive; the precipitation silica is divided into traditional precipitation silica and Special precipitation method white carbon black, the former refers to silica produced with sulfuric acid, hydrochloric acid, CO2 and water glass as the basic raw materials, the latter refers to the use of hypergravity technology, sol-gel method, chemical crystallization method, secondary crystallization Silica produced by special methods such as the reverse micellar microemulsion method or the reverse micellar microemulsion method. Precipitated silica is mainly used as reinforcing agent for natural rubber and synthetic rubber, toothpaste friction agent, etc. Fumed silica is mainly used as a reinforcing agent for silicone rubber, coatings and unsaturated resin thickeners, and ultra-fine silica gel and aerogel are mainly used as coating matting agents, thickening agents, plastic film opening agents, etc.

Benefiting from the growth in demand in tire manufacturing, silicone rubber industry, coatings industry, new energy and other fields, it is expected that the average annual growth rate of my country's precipitation silica (silicon dioxide) will be about 10% in the future. In 2015, Asia will become a big market for highly dispersed silica, and its demand growth rate will be much higher than the global average growth rate of 9%, reaching 15% or higher. China accounts for 40% of the Asian market and will become the largest single market in the world.

What are the traditional methods for preparing silica?

The traditional method of preparing white carbon black is to use sodium silicate, silicon tetrachloride and ethyl orthosilicate as silicon source. Except for sodium silicate, other costs are very high. The new method uses cheap non-metallic ore as silicon source, which greatly reduces the production cost of silica.

traditional method

(1) Gas phase method

Mainly chemical vapor deposition (CAV) method, also known as pyrolysis method, dry method or combustion method. The raw materials are generally silicon tetrachloride, oxygen (or air) and hydrogen, which are reacted at high temperature. The reaction formula is:

SiCl4+ 2H2+ O2—>SiO2+4HCl

Air and hydrogen are respectively pressurized, separated, cooled and dehydrated, dried on silica gel, filtered by dust removal and sent to the synthesis hydrolysis furnace. After the silicon tetrachloride raw material is sent to the rectification tower for rectification, it is heated and evaporated in the evaporator, and is sent to the synthesis hydrolysis furnace with the dried and filtered air as the carrier. After silicon tetrachloride is gasified at high temperature (flame temperature 1000~1800°C), gas phase hydrolysis is carried out with a certain amount of hydrogen and oxygen (or air) at a high temperature of about 1800°C; the fumed silica particles generated at this time Fine, form aerosol with gas, and it is not easy to capture, so it is first aggregated into larger particles in the aggregator, then collected by the cyclone separator, and then sent to the deacidification furnace, and the fumed silica is purged with nitrogen-containing air to A PH value of 4 to 6 is the finished product.​​

(2) Precipitation method

The precipitation method is also called the sodium silicate acidification method, which uses water glass solution to react with acid, and obtains white carbon black through precipitation, filtration, washing, drying and calcination. The reaction formula is:

Na2SiO3 + 2H+ —> Silica + 2Na+ + H20

Most domestic production enterprises use the precipitation method.

Silica is roughly divided into precipitated silica and fumed silica according to the production method.

Silica is a general term for white powdery X-ray amorphous silicic acid and silicate products, mainly referring to precipitated silica, fumed silica and ultrafine silica gel, also including powdered synthetic silicic acid Aluminum and calcium silicate, etc.

Silica is roughly divided into precipitation silica and fumed silica according to the production method. Fumed silica is a white amorphous flocculent semi-solid under normal conditions.

Transparent solid colloidal nanoparticles (particle size less than 100nm), non-toxic, with huge specific surface area. The fumed silica is all nano-silica, the product purity can reach 99%, and the particle size can reach 10~20nm, but the preparation process is complicated and expensive; the precipitation silica is divided into traditional precipitation silica and Special precipitation method white carbon black, the former refers to silica produced with sulfuric acid, hydrochloric acid, CO2 and water glass as the basic raw materials, the latter refers to the use of hypergravity technology, sol-gel method, chemical crystallization method, secondary crystallization Silica produced by special methods such as the reverse micellar microemulsion method or the reverse micellar microemulsion method. Precipitated silica is mainly used as reinforcing agent for natural rubber and synthetic rubber, toothpaste friction agent, etc. Fumed silica is mainly used as a reinforcing agent for silicone rubber, coatings and unsaturated resin thickeners, and ultra-fine silica gel and aerogel are mainly used as coating matting agents, thickening agents, plastic film opening agents, etc.