According to the accepted defoaming theory, a substance that can be used as a defoamer for a coating system usually needs to meet two points: one is to have a lower surface tension than the application system; the other is to be incompatible with the application system. Since the mineral oil type defoamer will have an adverse effect on the gloss of the paint film surface, the silicone type defoamer is more commonly used in high-grade water-based coatings. As shown in the figure above, the molecule contains 15 organosiloxane units and is a hydrophobic unit. Its polyether structure contains 8 PO units and 2 EO units, so the whole is also a hydrophobic unit. Therefore, in the aqueous coating system, the above structure The polyether silicone oil is hydrophobic as a whole, and it contains organosiloxane segments with low surface tension, which meets two necessary conditions for defoamers in aqueous systems. Therefore, the polyether modified silicone oil can be used as an aqueous coating system. Defoamer.
In addition, the organosiloxane segment of the main chain of the additive contains 10 unmodified units and 5 modified units, and the modification ratio is high, so the silicone defoamer has a better performance in water-based coating systems. It is safe to use and has less tendency to cause paint film malaise.