Silicone defoamer is a type of defoamer, which consists of organosilicon compounds and other additives. They are commonly used to eliminate air bubbles and foam in liquids, especially in the chemical, petroleum, pharmaceutical and food industries.
The advantage of silicone defoamers is that they can eliminate various types of foam, including high foam and low foam, and have excellent stability and compatibility during use. They also maintain good defoaming properties in the presence of surfactants, which makes them more suitable for certain applications.
Silicone defoamer use
The following are the six major applications of silicone defoamers:
(1) Sizing process: water-emulsion type silicone defoamer, such as: silicone polyether, the amount added in the sizing tank is 0.2¬0.25g/L
(2) Chemical fiber oil: Add 0.02¬0.04% water emulsion type defoamer to chemical fiber oil. The formula of chemical fiber oil should contain silicone oil.
(3) Desizing and refining: use polyether-containing silicone.
(4) Bleaching: strong acidity, silicone defoamer.
(5) Dyeing: silicone emulsion defoamer. It is best to use polyether silicone for jet dyeing, high-temperature defoaming, low-temperature water-soluble, and non-staining fabric.
(1) Drilling: Ethyl silicone oil (or methyl silicone oil layer emulsion) is used as mud additive.
(2) Oil recovery: oil and gas separation, defoaming rods. The melting point is 2.8¬13.9°C higher than the wellhead foam temperature.
(3) Natural gasoline absorption: make 2% solution of simethicone with gasoline.
(4) Oil and gas separation and demulsification:
A. Oil and gas separation, adding 0.025~0.0065mg/Kg to crude oil can increase production capacity;
B. Demulsification: The crude oil separated from oil and gas is generally micro W/O type emulsion, adding about 0.2mg/Kg of a suitable defoamer can achieve the effect of demulsification and defoaming.
(5) Refining: vacuum distillation with defoamer added, the color of the distillate is improved, and the distillate range is widened. Diesel solution with silicone oil is commonly used.
(6) High-energy fuels (internal combustion, jet, aviation fuel) use cyanoalkylpolysiloxane to disperse in high-flash point kerosene, and then add them to high-energy fuels as an efficient defoamer.
(7) Asphalt and residual oil: the amount of silicone oil added is 0.2×10 -6 to 2.0×10 -6
(8) Delayed coking, decoking, descaling: reference amount of defoamer added: 0.05～100×10 -6
(9) Defoaming drilling fluid: high-viscosity sulfonate metal salt (calcium petroleum sulfonate: sodium sulfonate pitch = 1:1), the amount of siloxane added is about 100-400×10 -6 or 5-15mg/Kg, Sulfonate:siloxane close to 1:1 is better.
(10) Lubricating oil: such as internal combustion engine, automobile lubricant, metal processing fluid, compressor oil, etc., when adding silicone oil for defoaming, it is because of the following advantages:
A. It is insoluble in lubricating oil and is in a dispersed state, which is beneficial to absorb on the bubble film and break the bubble;
B. It has an alkyl group similar to mineral oil, which can squeeze into the bubble film and weaken the molecular gravity;
C. Low surface tension and good penetration. When adsorbed on the surface of the bubble film, the local surface tension is reduced, and the bubble is broken due to the uneven surface tension of the bubble film. Use silicone oil with low viscosity as heavy oil, and add 1~10×10 -6 . In addition, alkyl polyacrylate is also better, and has better gas release properties. Branched-chain amines can be added to crude gasoline and naphtha, and then added to lubricating oil. They can also be used as defoamers. The amount added is 0.05-1%. This defoamer can be added to metal cutting fluids.
(1) Pulping: Silicone emulsion defoamer (90g/T paper).
(2) Coated paper: coating coating, paper for printing pictorials after calendering, non-silicon defoaming agent is generally used for coating air bubbles.
(3) Sewage treatment: Water-emulsion type silicone defoamer.
Application in coatings and inks
I. Requirements for defoamers in coating production:
(1) It has a certain affinity with the active substance on the surface of the foam, but it should be insoluble and insoluble in the bubble liquid;
(2) The surface tension is lower than that of the bubble liquid, and has a lower HLB value;
(3) The emulsion (latex) should be stabilized;
(4) After the coating is formed into a film, it cannot cause fish eyes and shrinkage cavities;
(5) Defoamer for water-based coatings: Use insoluble substances in water, such as mineral oil, higher alcohols, and silicone resins. Silicone is the best defoamer for water-based coatings.
Defoamer for non-aqueous coatings: commonly used substances that are difficult to dissolve in organic solvents, such as lower alcohols, silicone resins (the amount of silicone resin should be appropriate, excessive amount is easy to shrink and crack, and now more modified silicone resins are used or emulsified silicone resin)
II. Recommended silicone defoamers for water-based coatings:
(1) The mixture of silicone oil and hydrophobic SiO2 is applicable : epoxy resin, pouring coating, dosage 0.3%; thermoplastic acrylic resin, spray coating, dosage 0.3%
(2) The mixture of polyether polysiloxane and hydrophobic SiO2 is applicable: thermosetting alkyd resin, the amount of dipping is 0.3%, and the amount of scraping is 0.1 %
(3) The mixture of hydrophobic SiO2, hydrocarbons and silicone oil is applicable: thermoplastic acrylic resin, printing and ink, dosage 0.1%; air-drying acrylic resin, pouring coating, dosage 0.5%.
(4) Silicone oil and hydrophobic SiO 2 mixture emulsion is applicable: alkyd modified styrene-acrylic resin, pouring coating, dosage 0.5%.
Silicone defoamer for detergent industry
Polysiloxane and modified sodium tripolyphosphate are used as powder detergent additives, and the emulsion of simethicone oil (1500c.s) containing 2-6% SiO2 is mixed with anhydrous sodium tripolyphosphate, and the amount of emulsion is 10 ~40%, forming hydrates as additives.
Metal cleaning fluid requires alkali resistance, and it is best to be transparent and have defoaming activity when added to liquid products.
Silicone defoamer for food industry
Food-specific polysiloxane resin: dimethyl polysiloxane as the main body, containing less than 15% SiO 2 When the food is an aqueous solution, use its emulsified product, and other oil-based products can be used directly, and the dosage is controlled.