Hubei anti-settling agent is a kind of paint that has the advantage of rheology control. It makes the paint thixotropic and greatly improves the viscosity. Most of the thickeners discussed in the previous chapter can give the paint thixotropy. Anti-settling agents play an important role in modern coatings, and have an important impact on the production, storage, coating and film performance of coatings. Therefore, their use has been paid more and more attention, and new varieties with better performance have been continuously developed.
At present, the variety of anti-settling agents is relatively complete, and new products are constantly appearing, which can basically meet the requirements of modern coatings. The development technology of anti-settling agents has two directions: one is to improve the performance of the original product, enhance its use effect in coatings, ensure the safety of use, and facilitate the use; the second is to develop new varieties to continue to meet the needs of modern high-performance coatings. New requirements are constantly emerging.
The precipitation of fumed silica is very beneficial to the storage of coatings, especially certain pigments such as metal powder and flakes, which are very easy to precipitate and cannot be completely suspended. Using fumed silica can ensure that it is dispersed without precipitation. In completely non-polar liquids, such as hydrocarbons and halogenated hydrocarbon solvents without hydrogen bonding ability, the viscosity recovery time is only a fraction of a second; in polar liquids, such as those with hydrogen bonding tendency Among amines, alcohols, carboxylic acids, aldehydes, and glycols, the recovery time is as long as several months, which depends on the concentration of fumed silica and its degree of dispersion. Fumed silica is pre-dispersed and added to In the finished paint, in order to improve the dispersion quality, a high-speed disperser or a three-roller is usually used. If the dispersion is not sufficient, the paint film will have particles, which will affect the gloss.
It is reported in the literature that fumed silica is added as an anti-settling agent to copper-acrylic resin conductive coatings. Tests have shown that fumed silica can make thermoplastic acrylic resin thixotropic and prevent the sedimentation of filler particles, but the addition amount is too high. Many, the coating is in a gel state, and the conductivity of the coating is reduced.