Stability of Carbon Black Dispersion for Gel Ink

Different kinds of dispersants were tested and the carbon black dispersion for gel ink was prepared. In order to characterize the stability of carbon black dispersion, a centrifugal separation-absorption spectrophotometry method was proposed and verified experimentally. The dosage of the dispersant was optimized. The effect of sand milling time on the storage stability of dispersion was investigated. The results indicated that the block copolymer with aromatic rings was the good dispersant for carbon black aqueous dispersion. The good storage stability of dispersion was achieved under the condition of 2 h sand milling by adding 20%(ω) of ammonium solution of styrene-maleic anhydride resin based on the dry weight of carbon black. The mean particle diameter of the fresh dispersion was 117.1 nm and became 160.0 nm after 15 d storage. And the gel ink prepared with this dispersion also showed good storage stability and writing properties.