Silicone emulsion type defoamers are generally oil-in-water (O/W) emulsions, ie water is the continuous phase and silicone oil is the discontinuous phase. It is premixed with silicone oil, emulsifier and thickener, then gradually mixed with water, and finally repeatedly ground in a colloid mill until a desired emulsion is obtained.

Silicone oil emulsion defoamer is the most widely used and defoamer in silicone defoamer. It is characterized by easy dispersion in water systems and can be widely used as a defoaming agent for aqueous systems. When used, the emulsion is directly added to the foaming system to obtain a good defoaming effect. In order to improve the defoaming effect and measurement accuracy of the emulsion, it is generally not necessary to directly use more than 10% of the concentrated silicone oil emulsion: instead, it is first diluted with cold water or directly with a foaming liquid to 10% or less. Do not use a liquid that is overheated or too cold to dilute, otherwise it will cause the emulsion to break. The stability of the emulsion will be deteriorated after dilution, and stratification (bleaching) may occur during storage, that is, demulsification. Therefore, the diluted emulsion should be used up as soon as possible. If necessary, a thickener may be added to increase the stability of the emulsion. For batch operation, the silicone oil emulsion can be added one time before the operation of the system, or it can be added in batches; for continuous operation, the silicone oil emulsion should be continuously or intermittently added at the appropriate part of the system.

When using an emulsion type defoamer, special consideration should be given to the temperature and acidity and alkalinity of the foaming system. Because the silicone oil emulsion is more delicate and exceeds its range of use, the emulsion will break prematurely and become inefficient or ineffective. (The amount of the silicone oil emulsion is generally 10 to 10 ppm by weight of the foaming liquid (in terms of silicone oil). Of course, there are also less than 10 ppm and more than 100 ppm in special cases. The optimum amount is mainly determined by experiments.

Most of the silicone oil emulsion type defoamers are oil-in-water type. Depending on the type of silicone oil, silicone oil emulsion defoamers are of the following types:

1. Silicone oil emulsion based on dimethyl silicone oil
This type of defoamer is formulated from dimethyl silicone oil plus emulsifier and water. It can be widely used in fermentation, food, paper, fiber, pharmaceutical, synthetic resin and so on.

2. Silicone oil emulsion based on methyl ethoxy silicone oil
These defoamers are made from methyl ethoxy silicone oil and a compounding agent.

3. Silicone oil emulsion based on ethyl silicone oil
In recent years, silicone defoamers have progressed toward the silicone-polyether block copolymerization (or graft copolymerization). Such defoaming agents have the characteristics of silicone and polyether, so that the defoaming force is greatly improved; the silicone-polyether copolymerized defoaming agent can also be called a self-emulsifying silicone defoaming agent, which is Blocking (or grafting) a hydrophilic oxyethylene chain or an oxyethylene oxypropylene chain in a silicone molecular chain to bond a hydrophobic siloxane moiety with a hydrophilic polyether, such a molecule having a larger The polarity, as a defoaming agent, has a large spreading factor, can be uniformly dispersed in a foaming medium, and has high defoaming efficiency, and is a new type of high-efficiency defoaming agent. This type of self-emulsifying silicone oil which does not require the use of an emulsifier, the defoaming effect is quite satisfactory for some systems, and it is particularly suitable for occasions where it is not suitable to use a general silicone oil emulsion and a general silicone oil emulsion.