Method for producing N, N'-dimethyl-perylene-3,4,9,10-tetracarboxylic acid diimide in the form of highly opaque pigment

摘要

According to the invention, the pigment is prepared in a high-hiding pigmentary form using the known reaction of perylene-3,4,9,10-tetracarboxylic dianhydride with methylamine by using per mole of perylene-3,4,9,10-tetracarboxylic dianhydride at least 3 times the molar amount of methylamine in at least 5 times the weight of water, based on the weight of the dianhydride, carrying out the reaction at a temperature of from 40 to 200 DEG C and distilling off excess methylamine no earlier than after the perylene-3,4,9,10-tetracarboxylic dianhydride used has reacted to form methylammonium salts of the corresponding N,N'-dimethyldicarbamoylperylenedicarboxylic acids, the temperature being set after and optionally even in the course of the formation of the N,N'-dimethylperylene-3,4,9,10-tetracarboxylic diimide to 140 - 200 DEG C for some time to form a highly crystalline pigmentary form, then grinding the resulting aqueous suspension of the highly crystalline crude pigment, which has a median particle size D50% (weight distribution) of from 0.15 to 0.4  mu m and a median ratio q50% (weight distribution) of length to width of the pigment particles between 10:1 and 3:1, with or without intermediate isolation, until the median particle size is from 0.1 to 0.2  mu m and the median ratio of length to width of the pigment particles is less than 5:1, and treating the resulting prepigment in an aqueous suspension or following addition of an organic solvent in an aqueous-organic medium with heat until the pigment has a median particle size of from 0.125 to 0.4  mu m and a median ratio of length to width of pigment particles of 4:1 or less. …??The pigment produced according to the invention is suitable for pigmenting macromolecular organic materials, more particularly for pigmenting automotive coatings of the type of the alkyd-melamine resin or acrylic-melamine resin baking finishes or of the type of the two-part lacquers based on polyisocyanate-crosslinkable acrylic resins.