Hydrogen Peroxide → Quinacridone

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Reaction Steps

A one-liter flask equipped with a thermometer, stirrer and condenser is charged with 50 g 6,13-dihydroquinacridone, 250 ml methanol, 36 ml water, 0.6 g phthalimidomethyl quinacridone as crystal phase director and particle size reducing agent and 75 g 50% aqueous sodium hydroxide. The mixture is stirred under a slow flow of nitrogen at reflux temperature for one hour generating the corresponding 6,13-dihydroquinacridone-di-sodium salt. 1.2 g 2,7-anthraquinone-disulfonic acid sodium salt is added and the resulting mixture is further stirred at reflux for 10 minutes. Subsequently, 91.4 g of an aqueous 17% hydrogen peroxide solution are added at a rate of 0.3 ml/minute maintaining reflux temperature under a slow nitrogen flow. The resulting bright red suspension is diluted with 100 ml cold water, stirred for 5 minutes and then filtered at 50–60° C. The presscake is washed with hot water then dried yielding a high chroma red gamma quinacridone pigment, which shows less than 100 ppm catalyst residues when analyzed by HPLC.

Provenance & Evidence