Defoamers (defoamers, defoaming agent) is a kind of auxiliary agent. Its function is to eliminate the foam formed by materials in the production process. There are many defoamers with different ingredients. There are many kinds of defoamers, such as shear resistant defoamer, high temperature resistant defoamer, acid and alkali resistant defoamer, solid defoamer, silicon free defoamer, silicone defoamer, mineral oil defoamer, silicon polyether defoamer, polyether defoamer, etc.            (1) Functions of active ingredients: breaking and defoaming, reducing surface tension: representative substances: silicone oil, polyether, higher alcohol, mineral oil, vegetable oil, etc. [1] (2) emulsifier function: make the active ingredients disperse into small particles, which is convenient for dispersing in water and has better defoaming and antifoaming effect. Representative products: nonoxyphenol polyoxyethylene ether, soap salt, Op series, Tween series, Sipan series, etc. (3) Carrier function: it is conducive to the combination of carrier and foaming system, and easy to disperse into the foaming system. When the two are combined, its own surface tension is low, which is conducive to foam suppression, and can reduce the cost. Representative: solvent other than water, such as aliphatic hydrocarbon, aromatic hydrocarbon, oxygenated solvent and so on. (4) emulsifying assistant function: make emulsifying effect better. Representative: * dispersant: hydrophobic silica, etc. * tackifier: CMC, polyethylene ether, etc.