Application fields of silicone defoamer
1. Mechanism of action: Mechanism of action: The ability of silicone defoamers or foam suppressors is due to their very low surface tension. Silicone compounds (silicone oil) interfere with the surface tension of the gas-liquid interface, resulting in a defoaming effect. When silicone is added to the foam medium, small particles of silicone oil fall to the surface of the bubble, effectively reducing the surface tension of the contact point, causing a weak point on the outer skin of the bubble, thereby causing bubble breaking. The best defoaming activity standard can be described as follows: the free small particles of silicone oil must be completely, as quickly and effectively as possible dispersed into the active area. Silicone oil is quickly dispersed by virtue of the small proportion of SiO2 filler added during production and processing, which has a large surface area, and causes demulsification and bubble breaking outside the contact point of SiO2 particles. The squeezed foam causes an unstable state due to the rupture of the adjacent foam, which accelerates the effect of continuous bubble breaking until it reaches a stable state. If it is an emulsion defoamer, the emulsion is too stable, which will reduce the defoaming effect. When the stability is poor, it has greater activity. Therefore, it is necessary to balance stability and activity, and select organic silicon compounds with low solubility in water and oil phases but extremely high activity. The function of defoamers is also defined by three mechanisms: foam breaking, defoaming, and foam suppression. Foam breaking: relative to foam, entering the bubble from the air side and destroying the bubble. Foam suppression: entering the bubble from the liquid side and destroying the bubble. Defoaming: invading the bubble from the interface of the bubble, making the bubble float to the surface of the liquid. Defoamers include oil type, solution type, emulsion type, solid powder type and composite type.
All should have the following properties:
1. Strong defoaming power and low dosage;
2. Does not affect the basic properties of the system after addition;
3. Low surface tension;
4. Good balance with the surface;
5. Good diffusivity and permeability;
6. Good heat resistance, acid resistance and alkali resistance;
7. Chemical stability and strong oxidation resistance;
8. Gas solubility and good permeability;
9. Low solubility in foaming solution;
10. High physiological safety.
2. Types of silicone defoamers: Types of silicone defoamers:
1. Water-emulsion defoamer: With polydimethylsiloxane (silicone) as the main body and white carbon black complex, it is prepared into O/W type water-emulsion defoamer of various concentrations (suitable for water-based medium defoaming occasions) or made into high-concentration silicone paste under the action of surfactant (emulsifier), which is used by smearing or temporary dilution.
2. Oil system defoamer: Oil system defoamer: Silicone oil is carried by solvent and dispersed into the starting fluid. The solvent diffuses, and the silicone oil or droplets play a defoaming role (generally high and low viscosity silicone oils are blended) or made into silicone oil/mineral oil dispersion. Crude oil demulsification and dehydration: When crude oil accounts for a certain proportion, it is obtained in the form of W/O emulsion. If most of the water is not removed, this oil cannot be processed. The petroleum industry needs a large amount of organosilicon surfactants as demulsifiers. This is a white solid, and the surface tension of 1% aqueous solution is 20.6mN/m
3. Solid powder defoamer: Solid powder defoamer: Contains 2%~5% organosilicon defoaming components by mass and 98%~50% powdered solid carrier by mass.
