Defoamer (English name: defoamer, defoamer) is an auxiliary agent whose function is to eliminate the foam formed in the production process. There are many types of defoamers, and their ingredients vary widely.
  Defoamer is mainly composed of active ingredients, emulsifiers, carriers and emulsification assistants, among which active ingredients are the most important core part, which plays the role of breaking foam and reducing surface tension; emulsifier is to disperse active ingredients into small particles, so that Better dispersion in oil or water, better defoaming effect. The carrier occupies a large proportion in the defoamer, and the surface tension is not high, and it mainly acts as a support medium, which is beneficial to the effect of defoaming and defoaming, and can reduce the cost; the emulsification aid is to make the emulsification effect better.

  Polydimethylsiloxane (also known as silicone oil) is the main component of silicone defoamer. Compared with H2O oil and ordinary oil, silicone oil has smaller surface tension and is suitable for water-based foaming system and oil-based foaming system. In H2O and common oils, silicone oils have high activity and low solubility. Its basic characteristics are stable chemical properties, wide application range, low volatility, non-toxicity, outstanding defoaming ability, etc. The disadvantage is poor defoaming performance.

  Antifoams have many components:
  1. Natural oils (ie soybean oil, corn oil, etc.);
  2. Polyether defoamer (GP defoamer, GPE defoamer, GPES defoamer);
  3. Higher alcohols are linear molecules with strong hydrophobicity and weak hydrophilicity.
  4. Silicon, the most commonly used is polydimethylsiloxane, also known as dimethicone.
  Bleaching powder defoamer is a mixture of calcium hydroxide, calcium chloride and calcium hypochlorite. Its main component is calcium hypochlorite [Ca(ClO)2], and the effective chlorine content is 30%-38%. Bleaching powder is white or off-white powder or granules, with obvious chlorine odor, unstable, strong hygroscopicity, and easily decomposed by light, heat, water and ethanol. Bleaching powder dissolves in water, and its aqueous solution can turn litmus paper blue, and then gradually fade to white. In the presence of carbon dioxide in the air, hypochlorous acid can decompose, and in the presence of dilute hydrochloric acid, a large amount of oxygen can be produced.
  Active ingredient: ca(clo)2-calcium hypochlorite.

  Preparation: Pass chlorine gas into lime milk: 2cl2+2ca(oh)2=CaCl2+ca(clo)2+2h2o. Bleaching powder is produced by the reaction of chlorine gas and calcium hydroxide (slaked lime).
  Bleaching powder is easy to fail when exposed to air: Ca(ClO)2+H2O+CO2=CaCO3↓+2HClO.
  Since defoamer generally does not react chemically with other substances, the COD of water will not increase after adding defoamer, so it can be used with confidence.
  (1) The role of active ingredients: breaking and defoaming, reducing surface tension: representative materials: silicone oil, polyether, higher alcohol, mineral oil, vegetable oil, etc.
  (2) Emulsifier function: Disperse the active ingredients into small particles, which are easy to disperse in water, and better play the role of defoaming and suppressing foam. Representative materials: nonylphenol polyoxyethylene ether, soap salt, op series, Tween series, Span series, etc.
  (3) Carrier function: It is helpful for the combination of the carrier and the foaming system, and it is easy to disperse into the foaming system. When the two are combined, their own surface tension is low, which helps to suppress foam and can reduce costs. Representative materials: solvents other than water, such as aliphatic hydrocarbons, aromatic hydrocarbons, oxygenated solvents, etc.
  (4) Emulsifying auxiliary function: make the emulsifying effect better. Representative: * Dispersant: Hydrophobic silica, etc. ; Tackifier: CMC, polyvinyl ether, etc.