| abstract |
An improved process for producing a ground crude pigment by grinding in the dry state a crude pigment composed of a phthalocyanine compound or a polycyclic organic pigment compound, is achieved by using a grinding apparatus comprising a cylindrical receptacle having an axis in the longitudinal direction, a stirrer having a rotating shaft disposed along the axis of the receptacle and at least two pairs of arms, each pair having arms fixed to the rotating shaft and extending outwardly toward the side wall of the receptacle, and steel balls as a grinding medium filled in the receptacle. |