Something you don't know about Silicone emulsion Isomeric alcohol ethoxylates
In the previous article, we mainly introduced the usage of silicone emulsion as a surfactant. Today, we will talk about another usage of silicone emulsion isomeric alcohol ethoxylates.
What is silicone emulsion defoamer?
Silicone emulsion defoamers are generally oil-in-water (O/W) emulsions, that is, water is the continuous phase and silicone oil is the discontinuous phase. It is to pre-mix the silicone oil, emulsifier and thickener, and then gradually add water and stir evenly, and finally grind repeatedly in the colloid mill until the desired emulsion is obtained.
Silicone emulsion defoamer is one of the most widely used and the largest amount of silicone defoamers. It is characterized by being easily dispersed in water systems and can be widely used as a defoamer in water phase systems. When in use, adding the emulsion directly to the foaming system to obtain a good defoaming effect. In order to improve the defoaming effect of the emulsion and the accuracy of measurement, generally do not directly use more than 10% concentrated silicone oil emulsion: instead, dilute it to less than 10% with cold water or directly with foaming liquid. It is contraindicated to use hot or cold liquid to dilute, otherwise it will cause the emulsion to break. After the emulsion is diluted, the stability will become poor, and the phenomenon of layering (oil floating) may also occur during storage, that is, demulsification. Therefore, the diluted emulsion should be used up as soon as possible. If necessary, thickeners can be added to improve the stability of the emulsion. For the batch operation process, the silicone oil emulsion can be added at once before the system operation, or it can be added in batches; for the continuous operation process, the silicone oil emulsion should be added continuously or intermittently at the appropriate part of the system.
When using silicone emulsion defoamer, you should pay more attention to the temperature of the foaming system and the conditions of acidity and alkalinity. Because silicone oil emulsions are more delicate, if they exceed its range of use, the emulsion will demulsify prematurely and become inefficient or ineffective. (The amount of silicone oil emulsion is generally 10-10Oppm (calculated as silicone oil) based on the weight of the foaming liquid. Of course, there are also less than 10ppm and more than 100ppm under special circumstances. The most appropriate amount is determined by experiment.
The general silicone emulsion defoamers are mostly oil-in-water type. According to the different types of silicone oil, there are several types of silicone oil emulsion defoamers:
👉With dimethyl silicone oil as the main body of the silicone oil emulsion
This type of defoaming agent is made up of dimethyl silicone oil plus emulsifier and water, etc., and can be widely used in fermentation, food, papermaking, fiber, pharmacy, synthetic resin, etc.
👉With methylethoxy silicone oil as the main body of the silicone oil emulsion
This type of defoamer is made of methyl ethoxy silicone oil and a compounding agent.
👉With ethyl silicone oil as the main bodyof silicone oil emulsion
In recent years, silicone defoamers are moving towards the direction of silicone-polyether block copolymerization (or graft copolymerization). This type of defoaming agent has the characteristics of silicone and polyether, so the defoaming power is greatly improved; silicone-polyether copolymer defoaming agent can also be called self-emulsifying silicone defoaming agent, it is block (or graft) the hydrophilic ethylene oxide chain or ethylene oxide propylene oxide chain in the silicone molecular chain, so that the hydrophobic siloxane part and the hydrophilic polyether are combined together. This molecule has a larger as a defoaming agent, it has a large spreading coefficient, and can be uniformly dispersed in the foaming medium, and has a high defoaming effect. It is a new type of high-efficiency defoaming agent. This kind of self-emulsifying silicone oil without the use of emulsifiers, the defoaming effect is quite satisfactory for some systems, which are the best alternatives of common silicone oil emulsion.
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