| abstract |
Are obtained by condensing aromatic diamines with pyromellitic acid dianhydride (PMDA). Aromatic diamines are suitably derived from benzene, naphthalene, anthracene or pyridine. E.g. 1/10 mol. PMDA and 2/10 mol. o-phenylene diamine are intimately admixed and heated at 300 degrees C/3hrs. in an appts. which has been purged with N2. The pigment dyestuff so formed is ground finely and used directly for colouring the plastic material. |