Patents Assigned to Hoechst Aktiengescellschaft
  • Patent number: 5614015
    Abstract: A process for the preparation of 4,10-dibromoanthanthrone pigment, which comprises first subjecting the crude 4,10-dibromoanthanthrone pigment, which is in the coarsely crystalline state, to wet milling in an aqueous medium in a stirred ball mill which is operated at a power density of more than 2.5 kW per liter of milling space and at a peripheral stirrer speed of more than 12 m/s under the action of grinding media with a diameter of less than 1.0 mm, until the desired degree of fine division is reached (millbase suspension), and then isolating the resulting pigment in a conventional manner; or subjecting the prepigment obtained in the wet milling to a treatment at elevated temperature (finish) in an aqueous medium, an aqueous-organic medium or a liquid aromatic compound, and then isolating the pigment.
    Type: Grant
    Filed: September 14, 1995
    Date of Patent: March 25, 1997
    Assignee: Hoechst Aktiengescellschaft
    Inventors: Manfred Urban, Gerhard Wilker