What is the principle of the defoaming agent ?-Iota

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Service > What is the principle of the defoaming agent ?

What is the principle of the defoaming agent ?

Silicone defoamers principles and guidelines in the paint and ink industry, bubble problem usually comes in several ways: First, paint pigments and fillers in the adsorption of air; second, adverse reactions resulting cured film bubble; and third, the production of paints and construction process into a mechanical bubble; fourth, the air in porous substrates adsorbed in the construction process to be brought to release air bubbles. In general, in a system composed of the pure liquid, the foam can not be generated even if a long-term stable, under the force of gravity will soon spontaneous break; Once in the system, comprising a number of surface-active additives, air bubbles there may be in the help surfactant long-term stable, leading to a variety of foaming problems. To solve the above problems of bubbles caused by various reasons, in addition to select suitable raw materials to avoid bubbles, add various types of defoamers is the primary means of coatings and inks industry to solve the foam problem. According to the currently accepted theory defoaming, a compound that can be used as defoamers if a system, the need to meet two conditions: First, is it going to incompatibility and the application system; second, it should have a ratio the application system a lower surface tension. Common paint and ink systems are some of the medium-polar system so the polar lower non-silicone coatings and inks used can effect defoaming additives. In comparison, due to the relatively lower surface tension silicone additives, and in which the surface of the distribution system, tend therefore more silicone additives are used as anti-foaming additives, silicon additives rather than as the surface tension is relatively high, the system may be internal to the surface of both the distribution, so the more the inner system function, is often used as defoaming agents. Further defoamers defoaming capacity depends also on the incompatibility of the two factors polarity and molecular weight of defoamer, for a normal coating resin, the lower the polarity of the molecules antifoaming agent, the molecular weight is larger, it is incompatible with the resin, the higher resistance. Due to the low surface tension of organic silicon compounds as well as most of the coating resin system is incompatible with the characteristics in the coatings industry, a large amount of silicone antifoam were to use. Typically the organosilicon compound may be represented by the following structure, wherein R is a variety of organic functional groups (such as an aromatic group, an alkyl group, a fluorocarbon group, a polyether, a polyester functional group) and the like, when n = 0, that is, the structure shown in dimethicone, when n0, the structure shown as silicone oil. With different R groups, modified silicone defoamer performance obtained is not the same when R is an alkyl group, a phenyl group, a polyether group is an organic group, the resulting ratio of the modified silicone oil is dimethyl better compatibility with the silicone oil antifoaming capacity will be appropriately decreased, while the use of security is greatly improved; when the R group is a fluorine-containing group, that is, the resulting fluorine-modified silicone antifoam defoamer , compared with the defoaming ability dimethicone larger significantly enhanced, while the use of security is decreased. Since the surface tension of most of the silicone antifoam are very low, so they tend to be able to play an extremely excellent defoaming effect is small when the amount of addition, and in a sufficient defoaming effect when added usually the amount is not enough to cause significant changes in the transparency of the system, it is often a silicone antifoam is widely used in the system and to maintain high transparency, a good defoaming effect. Also due to the low surface tension of silicone defoamers, and in the coating system, incompatible with the system and have very low surface tension of the material is often the main cause of the ills of the film, it is for the use of silicone defoamers , the use of safety issues often become a problem engineers need most attention. Also from the foregoing, since the silicone defoamer for defoaming efficiency, the ability to achieve a sufficient defoaming, when the addition amount is often still low, the compatibility of that time often do not significantly change, but even so, film ills still possible, that the use of silicone defoamers particularly strong anti-foaming ability of silicone defoamers, when there may be compatibility film defects in good time, so the choice of some defoamers high anti-foaming ability, especially when silicone anti-foaming, you need to pay great attention to the safety of its use inside the test system. For aqueous coating systems, along with the development of modern waterborne coatings industry, the conventional mineral oil as a substrate defoaming increasingly unable to meet the requirements, followed by a silicone defoamers are more and more applications to aqueous coating systems were. Silicone defoamers typically used in aqueous coating systems with silicone oil emulsion into two categories, which is usually caused by silicone oil emulsion in the emulsion, thereby performing defoaming. Advantages emulsion type antifoam is itself dispersed by emulsification into droplets has a defoaming action, it is not required at the time of polishing can be used directly. And since the content of the silicone oil-based defoamer is high, there is added a small amount of characteristics, and can be adjusted by adjusting the defoaming ability of the water-soluble silicone oil. And silicone defoamer in eliminating microbubbles have a greater advantage than the emulsion type defoamers.

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