초록 ▼

The present invention provides a process for preparing transparent perylimide pigments of the formula (I) in which u is a number from 0 to 8 and, if u>0, E is a chlorine or bromine atom and, where u>1, may be a combination thereof, which comprises wet-grinding a crude perylimide pigment in a li

The present invention provides a process for preparing transparent perylimide pigments of the formula (I) in which u is a number from 0 to 8 and, if u>0, E is a chlorine or bromine atom and, where u>1, may be a combination thereof, which comprises wet-grinding a crude perylimide pigment in a liquid medium in a stirred ballmill operated at a power density of from 1.0 kW per liter of milling space and at a stirrer tip speed of more than 12 m/s under the action of grinding media having a diameter of less than or equal to 0.9 mm, and isolating the resulting pigment.

대표청구항 ▼

1. A process for preparing transparent perylimide pigments of the formula (I) in which u is a number from 0 to 8 and, if u>0, E is a chlorine or bromine atom and, where u>1, is a chlorine or bromine atom or combinations thereof, which comprises wet-grinding a crude perylimide pigment in a liqu

1. A process for preparing transparent perylimide pigments of the formula (I) in which u is a number from 0 to 8 and, if u>0, E is a chlorine or bromine atom and, where u>1, is a chlorine or bromine atom or combinations thereof, which comprises wet-grinding a crude perylimide pigment in a liquid medium in a stirred ballmill operated at a power density of from 1.0 kW per liter of milling space and at a stirrer tip speed of more than 12 m/s under the action of grinding media having a diameter of less than or equal to 0.9 mm, and isolating the resulting pigment. 2. The process as claimed in claim 1, wherein the crude perylimide pigment has been prepared by melting 1,8-naphthalenedicarboximide with an alkali metal hydroxide to give a leuco form and oxidizing the leuco form, or by condensing perylene-3,4,9-10-tetracarboxylic acid, its salt or its anhydride with ammonia. 3. The process as claimed in claim 1, wherein wet grinding is conducted in an aqueous alkaline or neutral pH range. 4. The process as claimed in claim 1, wherein wet grinding is conducted from 5 to 60 minutes. 5. The process as claimed in claim 2, wherein perylene-3,4,9,10-tetracarboxylic acid, its salt or its anhydride is reacted with at least 2 times the molar amount of ammonia and an at least 3-fold amount by weight of water, based on the weight of the perylene-3,4,9,10-tetracarboxylic acid, its salt or its anhydride, at a temperature of from 50 to 200° C. and the resulting crude pigment is subjected to wet grinding in a liquid medium in a stirred ballmill operated at a power density of from 1.0 kW per liter of milling space and at a stirrer tip speed of more than 12 m/s under the action of grinding media having a diameter of less than or equal to 0.9 mm, and isolating the resulting pigment. 6. The process as claimed in claim 5, wherein from 3 to 6 times the molar amount of ammonia per mole of perylene-3,4,9,10-tetracarboxylic acid, its salt or its anhydride is used. 7. The process as claimed in claim 5, wherein from 5 to 15 times the amount by weight of water, based on the weight of perylene-3,4,9,10-tetracarboxylic acid, its salt or its anhydride, is used. 8. The process as claimed in claim 5, wherein excess ammonia is distilled off before wet grinding. 9. The process as claimed in claim 5, wherein the crude pigment in form of a suspension is passed on for wet grinding without being isolated. 10. A transparent perylimide pigment formed in accordance with the process of claim 1.