Most of the additives used in coatings are surfactants, which achieve the effects of leveling, defoaming, dispersion and improving adhesion by reducing the surface tension at the gas-liquid, liquid-solid or gas-solid interface. Organosilicon compounds have low surface tension and high surface activity. They are widely used in coating systems and are important types of coating additives.


When the leveling agent needs to be used in high-temperature systems (such as baking paint), due to the low decomposition temperature of polyether, it is easy to decompose during use, causing some surface defects of the paint film, such as poor recoating, shrinkage, etc. It is necessary to choose silicone oil modified with high temperature resistant groups (such as alkyl modified silicone oil, phenyl modified silicone oil, polyester modified silicone oil, etc.). Relatively speaking, alkyl modified silicone oil can not only provide leveling effect, It also has a good defoaming effect, but it has poor compatibility and is generally not suitable for use in varnishes. Phenyl silicone oil and polyester modified silicone oil have relatively good compatibility and are suitable for use in high-temperature varnish systems, while providing excellent compatibility and high-temperature resistance. With the development of technology, some leveling agents that combine silicone and acrylate have recently appeared. This type of leveling agent combines the advantages of both and has excellent early-stage leveling and late-stage leveling effects. According to their different chemical structures, they can be divided into acrylate-modified silicone leveling agents (organic silicone as the main chain, acrylate as the side chain) and silicone-modified acrylates. As defoaming agents for coatings, they usually require specific applications. The system has low surface tension and is incompatible with the application system. Due to its low polarity structure, silicone is incompatible with most coating resin systems, so it is widely used as a raw material for coating defoaming agents. Usually, polydimethylsiloxane with a relatively large molecular weight (10 000 to 100 000) can be used as a coating defoamer. Currently, this type of defoamer is widely used in heavy anti-corrosion and other systems. In order to improve the defoaming efficiency, some white carbon black can also be added as a synergistic component. In addition, due to the high defoaming efficiency of organic silicon, it has good effects at very low addition amounts. In order to facilitate the addition, the organic silicon defoaming agent is usually made into a lower concentration solution to adapt to actual production. need.

 

In solvent-based coating systems, in order to enhance the defoaming ability of the coating, fluorocarbon-modified silicone is used. By introducing fluorocarbon segments with lower compatibility and surface tension into the main chain of the organic silicon, the coating and the The compatibility of the system greatly improves the defoaming effect. Generally, the longer the fluorocarbon chain introduced, the better the defoaming effect. This type of defoaming agent is usually a high-end variety among silicone defoaming agents. In water-based coating systems, due to the high polarity of water-based resins, conventional polydimethylsiloxane has limited compatibility with the system and is difficult to be used directly as a defoaming agent. Polydimethylsiloxane often needs to be modified with polyethers, especially for applications in high-gloss systems. Generally, the higher the degree of polyether modification, the better the compatibility, but the defoaming effect will also decrease. Generally, it is necessary to select an appropriate modification ratio according to the difficulty of defoaming of the system to meet the defoaming ability. Under the conditions, the lower the silicon content, the better.