Silicone oil emulsion defoamer is generally oil in water (O/W) emulsion, that is, water is a continuous phase, silicone oil is a discontinuous phase. It premixed silicone oil, emulsifier and thickening agent, then gradually added water to mix it up, and then rubbed it repeatedly in the colloid mill until the desired emulsion was obtained.










Silicone oil emulsion defoamer is the most widely used and defoaming agent in silicone defoamer. It can be widely used as defoamer in aqueous system. When used, the emulsion can be added directly to the foaming system, and good defoaming effect can be obtained. In order to improve the defoaming effect of emulsion and the accuracy of measurement, it is generally not used directly more than 10% of concentrated silicone oil emulsion: first, it is diluted to 10% or less with cold water or directly with foaming solution. Taboo should be diluted with overheated or undercooled liquid, otherwise it will cause emulsion demulsification. The stability of emulsion will become worse after dilution, and layering (oil bleaching) phenomenon may occur in storage process, that is, demulsification. Therefore, the diluted emulsion should be used as soon as possible. If necessary, thickeners can be added to improve the stability of the emulsion. For batch operation, silicone oil emulsion can be added either before the system runs or in batches. For continuous operation, silicone oil emulsion should be added continuously or intermittently in the appropriate parts of the system.










In the use of emulsion defoamers, the temperature and acid and alkaline conditions of the foaming system should be taken into consideration. Because the silicone oil emulsion is more delicate, its emulsion will be demulsified earlier, and it will become inefficient or ineffective. The amount of silicone oil emulsion is generally 10 to 10Oppm of the weight of the foaming liquid (according to the silicone oil meter). Of course, under special circumstances, there are less than 10ppm and more than 100ppm. The optimum dosage is mainly determined by experiments.


















Generally, silicone oil emulsion defoamer is mostly oil in water. According to the different types of silicone oil, silicone oil emulsion defoamer has the following types:










1. silicone oil emulsion based on two methyl silicone oil






This kind of defoamer is made up of dimethylsilicone oil, emulsifier and water. It can be widely used in fermentation, food, papermaking, fiber, pharmacy, synthetic resin and so on.










2. silicone oil emulsion based on methyl ethoxy silicone oil






This kind of defoamer is made of methyl ethoxy silicone oil and complex agent.










3. silicone oil emulsion based on ethyl silicone oil






In recent years, silicone defoamers are developing towards block copolymerization (or graft copolymerization) of silicone polyether. This kind of defoamer has the characteristics of both silicone and polyether, so the defoaming force is greatly improved; the silicone polyether copolymer defoamer is also called self emulsifying silicone defoamer, which is a hydrophilic ethylene oxide chain or ethylene oxide propylene oxide chain in the silicone molecular chain, so that the hydrophobic siloxane part is combined with the hydrophilic polyether, Such molecules have large polarity, large spreading coefficient as defoamers, can disperse evenly in the foaming medium, and have high defoaming effect, so they are a new type of high-efficiency defoamers. The emulsifying effect of self emulsifying silicone oil without emulsifier is quite satisfactory for some systems. It is especially suitable for those unsuitable for general silicone oil emulsion and general silicone oil emulsion.