Coating additives are considered to be an important component of coating products, which can improve the production process, improve product performance, improve coating performance, reduce pollution to the environment, develop new coating special features, and launch a variety of functional water-based coatings.
Although the majority of additives used in coatings is not a high relative proportion, but often to enhance and improve the performance of coatings and coating film can play a very critical role. In some products even to the extent that it is inseparable, coating additives due to their different functions and a wide variety. According to incomplete statistics, it is estimated that there are several thousand kinds, mainly film-forming additives, wetting agents, dispersants, defoamers, plasticizers, thickeners, antifreeze agents, leveling agents, anti-mold agents and preservatives, pH regulators, etc.
Associative rheology modifiers introduce long-chain hydrophobic groups on the polymer backbone, so they can not only increase the viscosity of the water phase in the system, but also interact with other components in the system such as surfactants, Polymer latex particles interact with pigments, filler particles, etc., michelman eaa dispersion and associate to form a three-dimensional network structure. Under high shear rate, this association structure will temporarily loosen and reduce the viscosity of the system, but under low shear rate, the association structure will recover again and the viscosity will increase accordingly.
Therefore, the associative rheology modifier can not only increase the viscosity of the latex paint system, but also endow the system with a certain degree of thixotropy and better leveling and splash resistance.
The hydrophobically modified alkali-swellable acrylate copolymer has high thickening efficiency under low shear rate, and has suitable viscosity under medium and high shear, which can prevent paint splashing and sagging and increase the thickness of a coating At the same time, it also has ideal thixotropic properties, so that the viscosity recovery speed after the shear is removed is moderate, so the coating film has better leveling performance.
The hydrophobically modified cellulose ether also has good thickening efficiency and anti-sagging and leveling effects. The characteristic of hydrophobically modified polyurethane is that it provides lower viscosity at low shear rate and has excellent leveling effect, but the effects of thickening, anti-settling and anti-sagging are not ideal; while at high shear rate, it can provide better High viscosity, improve the brushing feel, increase the fullness of the coating film, and endow the system with strong splash resistance. The two types of rheology additives, hydrophobically modified alkali-swellable acrylate copolymer and hydrophobically modified polyurethane, are available in a variety of varieties, providing different low, medium and high shear viscosity and rheological properties. The user should be based on the application. The need to choose.
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