| abstract |
The invention relates to a process for the preparation of N, N'-dimethyl-perylene-3,4,9,10-tetracarboxylic acid diimidenusing the reaction ofnPerylene-3,4,9,10-tetracarboxylic acid dianhydride with monomethylamine, therebyncharacterized in that per mol of perylene-3,4,9,10-tetracarboxylic dianhydridenat least 2 times the molar amount of monomethylamine and at least 3 timesnWeight amount of water, based on the weight of the dianhydride, thenCarried out reaction at a temperature of 50 to 200 ° C, unreactednMonomethylamine distilled off, the crude pigment obtained in a liquid,naqueous or aqueous-organic medium on a stirred ball mill withna power density of more than 1.5 kW per liter grinding chamber and onenAgitator peripheral speed of more than 12 m / s is operated at whichnExposure to grinding media with a diameter equal to or less than 0.9 mmnwet-ground and the pigment obtained isolated; with the proviso that to anany time of the process, but at the latest during wet grinding,none or more additives from the group of pigment dispersants andnSurfactants are added. |