Most of the additives used in coatings are surfactants, which can achieve the effects of leveling, defoaming, dispersion and improving adhesion by reducing the surface tension of gas-liquid, liquid-solid or gas-solid interfaces. Organosilicon compounds have low surface tension and high surface activity. They are widely used in coating systems and are important varieties of coating additives. Silicone additives used in coating systems are divided into chemical components, mainly including silane and silicone oil, as shown in Figure 1. Silanes are mainly some small molecular compounds, which are mainly used as adhesion promoters, crosslinking agents and dispersants in coatings; the main component of silicone oil additives is modified silicone oil, by adjusting the relative molecular weight of the additives, the modified group Depending on the type and content of the group R and the type of the terminal functional group, various additives with different properties can be obtained.

1 Silicone additives used as paint leveling agents
The structure of the leveling agent for coatings is generally composed of two parts: a segment that is compatible with the system and a segment that is incompatible with the system and has a lower surface tension than the system. During the film-forming process, due to the separation and migration of the incompatible chain segments with low surface tension, the additives will spontaneously migrate to the surface of the coating system to form a monomolecular film, thereby providing a uniform surface tension for the system and eliminating the impact caused by the surface tension gradient. Various paint film surface ills caused.

Silicone leveling agent is an important category of coating leveling agents. Generally speaking, polydimethylsiloxane with low relative molecular mass (<5 000) can be used as leveling agent, but because of its relative The capacity is not good, the use is more restricted, and the leveling effect is not good enough, so it cannot be applied to high-end systems. At present, silicone leveling agents widely used in coatings are various modified silicone oils. According to different types of modification, there are mainly polyether modified silicone oils, polyester modified silicone oils, phenyl modified silicone oils, alkyl modified silicone oils Silicone oil, phenyl alkyl co-modified silicone oil and alkyl-polyether co-modified silicone oil, etc. Among them, polyether modified silicone oil can be adjusted in a wide range because of its structure, and its performance can cover a variety of different requirements, which can be applied to Various systems are the main varieties of silicone leveling agents at present.

When the leveling agent needs to be used in a high-temperature system (such as baking paint), due to the low decomposition temperature of polyether, it is easy to decompose during use, causing some disadvantages on the surface of the paint film, such as poor recoating, shrinkage, etc. At this time It is necessary to choose silicone oil modified with high temperature resistant groups (such as alkyl modified silicone oil, phenyl modified silicone oil and polyester modified silicone oil, etc.). Relatively speaking, alkyl modified silicone oil can provide leveling effect, It also has a good defoaming effect, but its poor compatibility makes it generally unsuitable for clear coats. Both phenyl silicone oil and polyester-modified silicone oil have 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 combined with silicone and acrylate have appeared recently. This type of leveling agent combines the advantages of both, and has excellent early leveling and post leveling effects. According to its chemical structure, it can be divided into two types: acrylate-modified silicone leveling agent (silicon is the main chain, acrylate is the side chain) and silicone-modified acrylate, while silicone-modified acrylate In addition to providing leveling effect, leveling agent can also provide anti-fouling effect.