The basic principles for the selection of pigment carbon black in ink:
The finer the particle size of ink carbon black, the larger the surface area, which makes the base material system have higher viscosity and greater thixotropy. Pigment carbon black is a substance with a large surface area and therefore has a certain hygroscopicity. The moisture absorption of ink carbon black is mainly determined by the surface area. Measures can be strengthened, especially in the process of packaging, storage and transportation to reduce the hygroscopicity of the product. Because moisture (moisture absorption) is too high will bring trouble to the processing process, so special packaging is required for some varieties of ink carbon black.
When the particle size decreases or the surface area increases, the blackness and viscosity increase, and the dispersibility and gloss decrease. When the structure increases, the blackness and gloss increase, and the viscosity and dispersibility increase. When the acid value increases, the blackness, dispersion and gloss increase, and the viscosity decreases.
The structure is the form of carbon black aggregates. Generally, the more chain branches, the denser the structure, the higher the structure, otherwise the lower the structure. Low-structure carbon black has stronger tinting strength, better brightness, and better blackness. Compared with high-structure carbon black, it is more difficult to disperse, so a dispersant with better dispersibility should be selected. Especially for high-pigment carbon black, if a suitable dispersant is not used, or a good dispersant is used but the dosage is insufficient, or the dispersant is somewhat incompatible with the resin system, the well-dispersed pigment particles are easy to flocculate.
The pH value is an important index to measure the surface oxidation degree of carbon black aggregates. The oxygen content of pigment carbon black and the acidic oxygen-containing groups on the surface determine the surface chemical properties of carbon black. There are few functional groups on the surface of furnace carbon black and a small amount of soluble salts. The carbon black itself is mostly neutral or weakly alkaline. Change the number of functional groups on the surface through surface oxidation treatment, make the PH value acidic, and improve the dispersion performance, viscosity, stability and fluidity of ink carbon black.