Preparation Of High Performance Nano Quinacridone Pigment

Colorants for jet-printing inks maybe classified as either water soluble dyes or pigments. Since water soluble dyes can impart extremely high ink stability and chroma, they are the primary choices for the first generation jet-printing inks. Dye-based inks are particularly suitable for high speed and wide format jet printings. Unfortunately, the printouts from the dye-based inks, however, only show very limited fastness properties, preventing the water soluble dyes from being used for outdoor applications and indoor photo products which need long term preservations. Therefore, people have inevitably turned their attentions to pigments while formulating the second generation jet inks. Due to their relatively large particle size, ordinary pigments normally have low tinctorial strength and poor transparency, and can not be used directly for the preparation of jet inks. In order to improve their color strength and transparency, and to retain their fastness properties, pigments have to be nanotized.One important part of this project was the preparation of quinacridone quinone, a quite effective crystal growth inhibitor for 2,9-dimethyl quinacridone, namely C.I. Pigment Red 122. Based on a new solid state oxidization process, quinacridone quinone was prepared by using either quinacridone or 6,13-dihydroquinacridone as starting raw materials, water as reaction medium and salt of persulfate as the oxidizer. The process itself was much more environmentally friendly than traditional oxidization process with metal-containing oxidizers. Oxidization parameters including temperature, amount of oxidizer, reaction time had been optimized in a systematic study. Quinacridone quinone products of relatively high yield had also been made. The structure of this compound was characterized with UV-Vis, FTIR, X-ray diffractometer and confirmed by comparing with references.The key objective of this study was the preparation of nano C.I. Pigment Red 122. A salt attrition process with twin Z-blade kneader had been adopted for pigment size reduction. Phthalimidomethyl quinacridone, 6,13-Dihydro quinacridone, quinacridone quinone, and barium salt ofβ-anthraquinone sulfonic acid were used, respectively, as crystal growth inhibitor during the attrition. Factors related to the salt attrition efficiencies such as attrition time, type of solvents, fineness of the salt, ratio of raw materials including salt, solvent, and the crystal growth inhibitor versus pigment had all been studied systematically. The particle size, crystal, heat stability, and color properties of the finished samples from the salt attrition had also been characterized by SEM, TEM, X-ray diffractometer, TGA, and Color Spectrometer respectively. The experiments suggested that salt attritions up to 8 hours with phthalimidomethyl quinacridone or quinacridone quinone of 5% on pigment, diethylene glycol as the solvent in the range of 1-2 parts on pigment, and 200-400 mesh salt of 8-12 parts on pigment were optimum for the preparation of pigment of size in the range of 20-35 nm and relatively narrow distribution. Color evaluation of the nano pigments indicated that the tinctorial strength and masstone transparency had all been improved significantly.