Application of Pigment Carbon Black in Carbon Ink

Carbon ink is a very important writing and painting tool in the process of office, drawing and learning. It uses carbon black as the main coloring material and has very considerable lightfastness, water resistance, and long-lasting colorfastness. With the increase of output year by year, carbon ink has now accounted for more than 20% of the national ink output. The main raw material carbon black in ink is also called pigment carbon black. The quality of pigment carbon black is the key to manufacturing ink. The writing fluency of ink and the suspension of carbon black in ink have always been topics of concern to manufacturers and consumers.

Generally speaking, the blackness index of pigment carbon black is divided into four categories. The blackness index is the relative branch measured by the carbon black meter. The reflected light intensity is displayed by the ratio of the standard reflected light intensity. If the blackness index is less than 70, we call it high-pigment carbon black, the index is between 70-80, we call it medium-pigment carbon black, and the index is between 80-90 is ordinary pigment carbon black, and the index is above 90 It is low pigment carbon black. It is not difficult to see from here that the smaller the blackness index, the higher its blackness.

In fact, no matter what method is used to produce carbon black, its physical and chemical properties are related to the surface characteristics of carbon black particles, which have a certain impact on the performance of carbon ink.

Take the particle size and specific surface area as an example, the smaller the particle size, the larger the specific surface area, the greater the absorption and scattering of light, and the blacker the carbon black. However, the particle size of carbon black generally has an irregular proportional relationship with its blackness. More incident light, and thus less reflected light, makes it darker when viewed with the naked eye. It is worth noting that the smaller the particle size of carbon black, the more difficult it is to wet, and the viscosity of the dispersion will increase. If the dispersion is not good, its tinting strength will decrease.

In terms of structure, the morphology of carbon black aggregates is critical for ink manufacturing applications. The more particles that make up the carbon black aggregate, the more complex the chain branch structure, we say that its structure is higher, we call it high-structure carbon black, otherwise it is low-structure carbon black. High-structure carbon black has a larger DBP value, and the viscosity of the ink produced by using it is also relatively large, the wetting time is longer, and the dispersing ability is good, but the blackness is lower and the tinting strength is lower. Low-structure carbon black is more difficult to disperse due to the large absorption force between carbon black aggregates, and because its voids are small and contain relatively less air, it is easy to be wetted. Low-structure carbon black has fewer aggregates, so its blackness and tinting strength will be higher.

In addition, the surface of carbon black contains many chemically adsorbed complexes, which are mainly due to oxidation in the production process or considered specific post-treatment. The complexes mainly contain carboxyl, quinone, propyl, phenolic Different forms of adsorption oxygen-containing groups such as radicals, hydrocarbon radicals, etc. These complexes act like surfactants, allowing the carbon black surface to be easily wetted, enhancing its dispersibility and post-dispersion stability, and reducing the tendency for particles to re-agglomerate.

The surface chemical properties of carbon black mainly depend on the production method of carbon black and the treatment method after oxidation, and are usually characterized by volatile matter and surface acidity (PH value). The general furnace pigment carbon black has a volatile content of 1% and the surface is alkaline. The surface of carbon black treated after oxidation is acidic, and the volatile matter content can be increased by more than 2%. In the manufacture of carbon ink, carbon black with more chemical adsorption oxygen-containing groups on the surface should be selected, especially carbon black with more strong hydrophilic groups such as hydrocarbon groups and carboxyl groups, so as to facilitate the long-term suspension of carbon black in water and make the ink more effective. good stability.