Fine division in the preparation of organic pigments
First Claim
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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Accused Products
Abstract
Organic polycyclic crude pigments are finely divided in an ecologically and economically advantageous manner by first of all subjecting 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. Pigments prepared in this way are particularly suitable as colorants for the pigmentation of paints, printing inks and plastics.
51 Citations
18 Claims
- 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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17. A process for the fine division of crude, coarsely crystalline quinacridone, perylene or dioxazine pigments, which comprises first of all subjecting said crude 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.
Specification