Dispersing Pigment Carbon Black in Water-Based Inks

The dispersion of pigment carbon black in water-based inks presents unique challenges due to the particle's strong aggregation tendency and high oil absorption capacity. These characteristics make it one of the most difficult pigments to disperse in paints. In paint formulations, pigment carbon black has a tendency to form unstable suspended particles, and even after initially well-dispersed pigments or finished paint products may re-aggregate during storage, leading to particle coagulation and increased viscosity, commonly referred to as "returning to coarseness and thickening."

Through improved dispersion techniques and oxidation treatments, the specific surface area of pigment carbon black can be increased, making it more porous and containing higher levels of volatiles (typically increasing to over 10%). In contrast, untreated pigment carbon black contains around 5% volatiles. The increase in surface volatiles enhances hydrophilicity and somewhat improves dispersibility.

In any application, pigments must be dispersed to a particle size that meets optical performance requirements. Pigment carbon black is the most challenging pigment to disperse among all pigments, and the quality of dispersion directly affects blackness, hue, hiding power, and ultimately, the end-user's experience.

Composition of Water-Based Inks

Water-based inks are composed of water-based resins, additives, pigments, and water. Pigment carbon black, as a solid component, serves as the colorant in the ink, being insoluble in water. The color saturation, tinting strength, and transparency of water-based inks are closely related to the properties of pigment carbon black. As a key solid component in water-based inks, pigment carbon black determines the visible color on printed objects to a large extent and significantly impacts the overall quality of the ink.

Key Factors Affecting Dispersion

The dispersion process of pigment carbon black is influenced by three primary factors:

1. Intrinsic Properties: The original particle size, structure, and surface groups significantly impact dispersion. Generally, smaller particle size, lower structure, and lower volatile content make dispersion more challenging, while larger particles and higher volatiles can facilitate dispersion to some extent.
2. User Formulation: The user's formulation, including base materials, solvents, and resin performance, significantly affects the final dispersion, especially the choice of resin for carbon black.
3. Dispersion Equipment: Different dispersion equipment yields varying results under the same conditions. Selecting the right dispersion equipment is crucial for engineers.

Understanding these factors is essential for achieving optimal dispersion of pigment carbon black in water-based inks, ensuring high-quality ink performance and user satisfaction.