The dispersion of carbon black is the most difficult among pigments used in paints, due to its strong aggregation and high oil absorption properties. There is a tendency for unstable suspension particles to form in paints, and initially dispersed color paste or finished paint products can re-aggregate during storage, causing particle coalescence and thickening. After improving dispersion and oxidative treatment, the specific surface area increases, becoming porous and containing volatile components (usually increasing to more than 10%), while the content of volatile components in untreated carbon black is only about 5%. With an increase in surface volatile components, the hydrophilicity increases and the dispersion improves to some extent. In the process of application, pigments need to be dispersed into microparticle states that meet optical performance requirements. Pigment carbon black is the most difficult pigment to disperse among all pigments, so the quality of dispersion directly affects the blackness, hue, and covering power, and therefore the final use effect for the user.
Water-based ink is composed of water-based resins, additives, pigments, water, and other raw materials. Pigment carbon black, as a pigment, is the solid component of the ink and the colorant of the ink, and it is a pigment that is not soluble in water. The color saturation, coloring power, transparency, and other properties of water-based ink are closely related to the properties of pigment carbon black. Pigment carbon black in water-based ink is a black solid powder. It is the main solid component of water-based ink and the visible color part printed on the object, which largely determines the quality of water-based ink.
The dispersion of carbon black is mainly influenced by the following three factors:
Intrinsic characteristics: the original particle size, structure, and various surface groups will have a significant impact on dispersion. Generally, smaller original particle size, lower structure, and lower volatile content make dispersion more difficult, while the opposite is relatively easier.
User formula: the user's formula, the properties of the base material, solvent, and resin will significantly affect the final dispersion, especially the choice of resin used with carbon black.
Dispersion equipment: different dispersion equipment has different dispersion effects under the same conditions. Choosing the right dispersion equipment is something that engineers must pay attention to.