Production of pulverous magnetic particle for developer

Abstract

Abstract PURPOSE:To obtain the uniform electrostatic chargeability and moderate electric resistivity of a magnetic toner and magnetic carrier by mixing a binder resin, magnetic powder and colloidal silica then melting and kneaking the same. CONSTITUTION:The compounding ratio of the binder resin and magnetic powder in pulverous magnetic particles is set at 20:80-80:20. A polymn. resin such as polystyrene, PE and polyether, a condensation resin such as a phenolic resin, urea resin and epoxy resin and the copolymer of these monomers are usable as the binder resin. The magnetic powder having 0.1-3mum average grain size is used, for which pulverous powder of magnetite, chromium dioxide or the like is usable as the magnetic powder. Magnetite is above all inexpensive and usable reliabily. The colloidal silica having <=0.1mu average grain size is used and is compounded at 0.01-10wt% with the magnetic particles by the mixed weight of the magnetic powder and the binder resin. If the magnetic powder, binder resin and colloidal silica are mixed by a dry process in the stage of kneading and melting the same, the fluidity of the mixture is improved and continuous kneading is permitted. The weight average grain size of the magnetic toner and magnetic carrier is made 5-40mum.

Inventors

• 👤 Yoshimi Amagai
• 👤 天貝　良美
• 👤 Hiroaki Yoshikawa
• 👤 吉川　博明

Bibliographic Details