The development of defoaming agent is mainly divided into four stages.The first class of defoaming agent, mainly composed of a variety of organic matter, such as: fatty acid, mineral oil, fatty amide, low alcohol, etc. This kind of defoaming agent is mostly natural material, little to the environment pollution, the price is low. Because the defoaming performance is relatively weak, for a large number of foam can not meet the production requirements.The second category is polyether defoamer CnH(2n+1)O(EO)a(PO)bH, polyoxyethylene chain segment (EO) is hydrophilic; Polyoxy-propylene group (PO) is an oil-loving group. The antifoaming agent has good antifoaming performance, no toxicity, no stimulation, and good dispersibility. In the actual production, the relative molecular weight of polyether and the proportion of EO and PO in the polyether chain segment are adjusted to meet the needs of various production fields. The main polyether defoaming agents in the market are straight chain polyether, ether amine, fatty acid polyoxyethylene ether, and isopolyether derivatives.The third category is silicone defoaming agent, which has better defoaming performance than the former two. Generally, silicone oil with larger molecular weight is insoluble in surfactant solution, while for small molecules, silicone oil is easily solubilized by surfactant molecules, which changes the composition of defoaming agent and weakens the defoaming performance. For the antifoaming agent mixed with silicone oil, it is insoluble in water and mineral oil, so it has strong anti-foaming ability and greatly enhances its anti-foaming effect. Because si-o and si-c bonds are relatively stable, they can be used in systems containing a small amount of acid, base and salt. Most of the silicone defoaming agents commonly used in industrial production are secondary processed products of silicone oil made by adding dispersing auxiliaries to silicone oil, which belong to liquid mixtures. In terms of appearance and fluidity, the mixture can be divided into five types: silicone paste, silicone oil, emulsion, solution and solid.The fourth kind of defoaming agent is polyether modified silicone oil defoaming agent. On the basis of previous generations of defoaming agent, the advantages of polyether and organosilicone are integrated, and the polyether chain segment is introduced into silicone oil chain segment, which has stronger defoaming and anti-foaming performance. Polyether modified silicone oil belongs to a new type of special organic silicon surfactants, using polyether containing double bonds with low hydrogen silicone oil through addition reaction, is a kind of unique performance of organic silicon non-ionic surface active agent, it keeps the high and low temperature resistance, weatherability, silicone mold release, hydrophobic nature and physical properties, such as inert, and polyether, without excitant, high surface activity, and the characteristics of easy to disperse, polysiloxane segment oil-wet, period of hydrophilic polyether chain, that created polyether modified silicone oil can dissolve in water can dissolve in oil phase, thus can be used as organic silicon surfactants; Polyether chain segments can also be used as emulsifiers to keep the properties of the emulsion stable and have good dispersion properties. Therefore, polyether modified silicone oil has a long-lasting defoaming effect in water system. Because polyether modified silicone oil has good heat resistance, shear resistance, acid and alkaline resistance, non-toxic and odorless, and stable storage, it is widely used, especially when silicone oil defoaming agent is difficult to solve the application.