A substance that can reduce the surface tension of water, solution, suspension, etc., prevent the formation of foam, or reduce or eliminate the original foam. [1] It should have the following properties: ① strong defoaming force, less consumption; ② adding to the foaming system does not affect the basic properties of the system, that is, it does not react with the defoaming system; ③ small surface tension; ④ good balance with the surface; ⑤ good heat resistance; ⑥ good diffusion and permeability, high positive spreading coefficient; ⑦ chemical stability, strong oxidation resistance; ⑧ good gas solubility and permeability The solubility of ⑨ in foaming solution is small, and the safety is high. [2]            Defoamers are widely used in food industry, paper industry, water treatment industry, oil production industry, printing and dyeing industry, coating industry, detergent industry, rubber latex industry, aerosol industry, daily chemical industry, pharmaceutical industry, dairy industry, etc.