| 摘要 |
PURPOSE:To obtain the titled fine particle aggregate useful as a filler for electrostatic recording material, etc., having low hydrophilic nature, improved weather resistance, whiteness, etc., by grinding acrylonitrile aggregated polymer particles satisfying a specific condition, classifying and pulverizing. CONSTITUTION:Firstly, polymer particles which have >=95wt% copolymerization amount of acrylonitrile, 1-8 reduced viscosity, 0.1-2mu particle diameters and contain no sulfonic group obtained by aqueous suspension polymerization method are aggregated, to give acrylonitrile aggregated polymer particles having >=10mu volume-average particle diameter. Then, the particles are ground and classified to give the aimed fine particle aggregate having 1-5mu volume-average particle diameter and <=0.05% number content of particles having >=8mu particle diameter. The grinding of the polymer particles is preferably carried out by blowing jet air flow from a jet air flow inlet 11 to a grinding zone 13 and making raw material particle collide with themselves while rotating them. |
