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Fine division in the preparation of organic pigments

  • US 5,626,662 A
  • Filed: 04/13/1995
  • Issued: 05/06/1997
  • Est. Priority Date: 04/21/1994
  • Status: Expired due to Fees
First Claim
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1. A process for the fine division of crude polycyclic organic pigments, which comprises first of all subjecting the crude, coarsely crystalline pigments to dry milling and wet-milling the resulting finely divided prepigments in aqueous suspension in a stirred ball mill which is operated at a power density of more than 2.5 kW per liter of milling space and a peripheral stirrer speed of more than 12 m/s under the action of grinding media having a diameter of less than or equal to 1 mm with the proviso that there is no inorganic salt present in the dry milling step.

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