Improved pigment dispersibility in thick inks based on increased molecular dispersion of poorly water-soluble block copolymers

For application as an aqueous ink, a low-acid-value and poorly water-soluble amphiphilic block polymer was successfully converted into an aqueous solution with a concentration of ≤ 5wt.%. This was achieved via neutralization with an alkaline solution after the preparation of a highly concentrated solution of the highly viscous alcohol. When cyan and magenta inks were prepared in aqueous solutions via this method, the pigment dispersibility was improved and the viscosity of each ink was reduced. In traditional ink preparation approaches, the pigments, polymers, and additives are often mixed and dispersed together, but the importance of dissolving polymers in advance has been confirmed in this study. Zeta potential measurements of the pigments showed that a more negative potential led to a more dispersible ink, likely due to a greater electrostatic repulsion closely related to the adsorption of dispersants. The development of highly concentrated aqueous polymer dispersion solutions of poorly water-soluble block copolymers has enabled more precise analysis between polymer structures and dispersion mechanisms for thick pigment dispersions, including zeta potential estimation to study adsorption and rheological dispersion characteristics. In general, the design of polymer dispersants is determined by ink tests, and the results are always affected by polymer solubility. This paper therefore demonstrates the possibility of widening the scope of polymer design for inks through improving polymer solubility.