White carbon black, also known as silica, scientific name precipitated hydrated silica. It is a high-tech inorganic fine chemical product, mainly composed of SiO2. The performance and appearance of carbon black are similar to that of white highly dispersed amorphous or flocculent powders, and they are also processed into particles as commodities. Lightweight, original particle size 0.3 μ The relative density below m is 2.319-2.653, with a melting point of 1750 ℃. It is insoluble in water and most acids, and when absorbed by water in the air, it becomes a fine particle that absorbs water. Soluble in caustic soda and hydrofluoric acid. Other chemicals do not react, do not decompose at high temperatures, and do not burn. It is chemically inert to substrates, active ingredients, and additives, and has good compatibility with many active ingredients commonly used in vitamins, hormones, fluorides, antibiotics, enzyme preparations, and cosmetics. Has high electrical insulation. Due to its porosity and large specific surface area, it has great dispersibility in raw rubber and exhibits high reinforcement performance in rubber. The surface modification of hydrophobic silica is easily soluble in oil, rubber, and plastics as reinforcing fillers, which will significantly improve its mechanical strength and tear resistance indicators. Due to different manufacturing methods, the physical and chemical properties and microstructure of silica may vary, resulting in different application fields and effects.

White carbon black can be roughly divided into precipitated white carbon black and gas-phase white carbon black according to production methods

White carbon black is the general term of white powder X-ray amorphous silicic acid and silicate products, mainly referring to precipitated silica, fumed silica and ultra-fine silica gel, as well as powder synthetic aluminum silicate and calcium silicate.

White carbon black can be roughly divided into precipitated white carbon black and gas-phase white carbon black according to production methods. Under normal conditions, gas-phase white carbon black is a white amorphous flocculent semi transparent solid colloidal nanoparticle (particle size less than 100nm), non-toxic, and has a huge specific surface area. Gas phase white carbon black is entirely made of nano silica, with a product purity of up to 99% and a particle size of 10-20nm. However, the preparation process is complex and expensive; Precipitation white carbon black can be divided into traditional precipitation white carbon black and special precipitation white carbon black. The former refers to silicon dioxide produced with sulfuric acid, hydrochloric acid, CO2 and water glass as basic raw materials, and the latter refers to silicon dioxide produced with special methods such as high gravity technology, sol gel method, chemical crystal method, secondary crystallization method or reverse micellar micro lotion method. Precipitated silica is mainly used as a reinforcing agent for natural rubber and synthetic rubber, as well as a friction agent for toothpaste. Vapor phase silica is mainly used as reinforcing agent, coating and unsaturated resin thickener of silicone rubber, and ultra-fine silica gel and aerogel are mainly used as coating matting agent, thickener, plastic film opening agent, etc.

Thanks to the growth in demand in the tire manufacturing industry, silicone rubber industry, coating industry, new energy and other fields, it is expected that the average annual growth rate of precipitated silica (silica) in China will be about 10% in the future. In 2015, Asia will become a major market for highly dispersed white carbon black, with a demand growth rate far higher than the global average of 9%, reaching 15% or higher. China accounts for 40% of the Asian market and will become the world's largest single market.

What are the traditional methods for preparing white carbon black?

The traditional method for preparing white carbon black is to use sodium silicate, silicon tetrachloride, and ethyl orthosilicate as silicon sources. Except for sodium silicate, other costs are very high. The new method uses inexpensive non-metallic minerals as silicon sources, greatly reducing the production cost of white carbon black.

Traditional methods

(1) Gas-phase method

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

SiCl4+2H2+O2->SiO2+4HCl

Air and hydrogen are respectively pressurized, separated, cooled and dehydrated, dried with silica gel, and filtered for dust removal before being sent to the synthetic hydrolysis furnace. Send the raw material of silicon tetrachloride to the distillation tower for distillation, heat and evaporate it in the evaporator, and use the dried and filtered air as the carrier to send it to the synthesis hydrolysis furnace. After gasification of silicon tetrachloride at high temperature (flame temperature 1000-1800 ℃), it undergoes gas-phase hydrolysis with a certain amount of hydrogen and oxygen (or air) at a high temperature of around 1800 ℃; At this time, the generated gas-phase silica particles are fine and form aerosols with the gas, which are difficult to capture. Therefore, they are first aggregated into larger particles in the aggregator, collected by a cyclone separator, and then sent to a deacidification furnace. The gas-phase silica is washed with nitrogen-containing air to a pH value of 4-6, which is the finished product. 

(2) Precipitation method

The precipitation method, also known as sodium silicate acidification method, 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+->White carbon black+2Na++H20

Most domestic production enterprises adopt the precipitation method.

White carbon black can be roughly divided into precipitated white carbon black and gas-phase white carbon black according to production methods

White carbon black is the general term of white powder X-ray amorphous silicic acid and silicate products, mainly referring to precipitated silica, fumed silica and ultra-fine silica gel, as well as powder synthetic aluminum silicate and calcium silicate.

White carbon black can be roughly divided into precipitated white carbon black and gas-phase white carbon black according to production methods. Under normal conditions, the white amorphous flocculent half of gas-phase white carbon black

Transparent solid colloidal nanoparticles (particle size less than 100nm) are non-toxic and have a huge specific surface area. Gas phase white carbon black is entirely made of nano silica, with a product purity of up to 99% and a particle size of 10-20nm. However, the preparation process is complex and expensive; Precipitation white carbon black can be divided into traditional precipitation white carbon black and special precipitation white carbon black. The former refers to silicon dioxide produced with sulfuric acid, hydrochloric acid, CO2 and water glass as basic raw materials, and the latter refers to silicon dioxide produced with special methods such as high gravity technology, sol gel method, chemical crystal method, secondary crystallization method or reverse micellar micro lotion method. Precipitated silica is mainly used as a reinforcing agent for natural rubber and synthetic rubber, as well as a friction agent for toothpaste. Vapor phase silica is mainly used as reinforcing agent, coating and unsaturated resin thickener of silicone rubber, and ultra-fine silica gel and aerogel are mainly used as coating matting agent, thickener, plastic film opening agent, etc.

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