White carbon black is a general term for fine powder or ultrafine particle like anhydrous and hydrous silica or silicate. It is a white, non-toxic, amorphous fine powder with a large content of SiO2 (more than 90%). At present, there are two common white carbon black in the market: vapor phase white carbon black and precipitation white carbon black. Precipitated silica (scientific name: precipitated hydrated silica) is mainly used in shoes, tires and other light colored rubber products. Other uses include as a carrier or flow agent in pesticide, feed and other industries, as a friction agent in toothpaste, and as a dispersant, anti sedimentation agent or matting agent in coatings. Vapor silica (also known as fumed silica) is a multifunctional additive. It is mainly used in the rubber field for room temperature vulcanized silicone rubber (RTV), heat vulcanized silicone rubber (HTV) and other fields. Other uses include coatings, adhesives, inks, chemical mechanical polishing, paper making, food and colloidal batteries. It can play a role in thickening, thixotropic, matting and anti sinking.


The production method of fumed silica is mainly chemical vapor deposition (CAV). This process is also called pyrolysis, dry process or combustion process. The preparation process is to send the silicon tetrachloride (or methyl trichlorosilane) raw material to the distillation tower for rectification, heat and evaporate in the evaporator, and send it to the synthetic hydrolysis furnace with the dried and filtered air as the carrier. The advantages of gas phase method are that the production process is relatively simple, the reaction conditions are easy to control, the product purity can reach 99.8%, the specific surface area is large, the activity is high, and the surface hydroxyl is less, which is suitable for the synthesis of high-purity white carbon black; The disadvantage is that there are active silicon hydroxyl groups on the surface, adsorbed water and preparation process, which lead to acid areas on the surface, making white carbon black hydrophilic, difficult to soak and disperse in the organic phase, high production cost, high product price, small application scope and low yield. It is difficult to control the specific operation of the production process of fumed silica, especially to produce high brand products (products with high specific surface area). The technical difficulties are the heat dissipation of the synthesis furnace, the operation control of the high-efficiency separator and the hydrogen chloride desorption. The most difficult to control are the gas phase equilibrium and gas-solid phase equilibrium of the system. In terms of surface modification, the large multinational companies all adopt the continuous dry surface modification process, and are developing towards high efficiency, energy conservation and environmental protection. Domestic research in this area is still in a backward state.


Precipitation method is also called wet method. The main raw materials are quartz sand, soda ash, industrial hydrochloric acid, sulfuric acid, nitric acid or carbon dioxide. The production process mainly includes sedimentation, filtration, drying and granulation. First, industrial sodium silicate is prepared by reacting quartz sand with soda ash using fuel oil or high-quality coal at high temperature; The industrial water glass is prepared into a dilute solution of a certain concentration with water, and then some acid is added under certain conditions to generate hydrated silica precipitation. According to the requirements of the finished product, it is filtered and washed in the roller filter press or plate filter press to remove excess water and reaction by-products to obtain white carbon black filter cake; The finished product is obtained through drying (usually spray drying). If further grinding or granulation treatment is carried out, a series of products can be obtained.