Preparation of Core-shell Composite Particles Containing a Dye Powder by a Droplet Coalescence Method

It was attempted to prepare core-shell composite particles containing a hydrophilic dye powder by a droplet coalescence method using liquid-liquid dispersion. Core particles composed of dye powder and oleic acid have been forced to coalesce with styrene monomer droplets, and then suspension polymerization has been performed to form the polystyrene shell. In the experiment, the number and diameter of styrene monomer droplets were mainly changed stepwise to promote coalescence between the core particles and the monomer droplets and to control the shell thickness. It was found that the core shell composite particles could be prepared by increasing the monomer droplet number at the constant impeller speed, because the coalescence frequency between the monomer droplets and the core particles increased with the monomer droplet number at the constant impeller speed. Moreover, the diameter and shell thickness of the core shell composite particles increased with the diameter of monomer droplets.