An important indicator of the quality of the defoamer is its dispersion effect. Only those with low solubility and large dispersibility can become the active ingredients of the antifoaming agent. As the main component of the defoaming agent, dimethyl silicone oil has small solubility and small dispersibility. It must be aided by white carbon black, emulsifiers and other dispersing aids to improve its dispersing effect. Vapor phase method white carbon black is divided into hydrophilic type and hydrophobic type. The hydrophilic type contains silicon hydroxyl bonds and can form hydrogen bonds with water molecules. It can promote the dispersion and stability of defoamers in water systems. Hydrophobic fumed silica is obtained by surface treatment of hydrophilic silica to reduce the Si-OH number of silica to an appropriate level. It can also be used in water systems to reduce silica in water. The degree of association of the system to achieve the best defoaming effect. The application of fumed silica in the defoamer is to make it with silica gel and dimethyl silicone oil, so as to improve its wettability with dimethyl silicone oil and dispersibility in silicone oil. The mixing method of silicon paste has certain influence on the stability and defoaming performance of silicon paste. When hydrophilic silica is used, due to the low compatibility between inorganic silica and silicone oil, in order to achieve the purpose of mixing, put silicone oil and silica in a kneader and mix at 150 ~ 180 ° C. Stir N2 for 2-7 hours to improve the wettability of silica and silicone oil. If hydrophobic silica is used,

The surface has been treated with organic matter, and its affinity with silicone oil is greatly improved. It can be stirred at 150 ° C for 2 to 5 hours under N2. Silicone paste made of fumed silica is transparent or translucent. The ratio is generally silicone oil: silica = (90-95): (10-5). Dimethyl silicone oil is generally selected at 25 ° C and 500-1000cp. Silicone oil and white carbon black can be selected with a specific surface area of 200m2 / g or more (BET method). As the active ingredient of silicone oil defoamer, silicone oil paste can be used directly or diluted with solvent, or self-emulsified with emulsifier or polyether modified silicone oil to achieve the purpose of defoaming. Due to the presence of SiO2 particles, the silicone oil can quickly spread in the foaming liquid, which improves the dispersion efficiency of the silicone oil, thereby improving the defoaming effect. Therefore, fumed silica is a very important dispersant in defoamers.