Hydrogen Peroxide → Quinacridone

Participants

Reaction Conditions

Reaction Steps

A one liter flask equipped with a thermometer, stirrer and condenser is charged with 50 g 6,13-dihydroquinacridone, 200 ml methanol and 5 g of the aqueous presscake of the nanosize quinacridone/naphthalene sulfonic acid formaldehyde polymer mixture according to Example 1 are stirred at 20-27° C. for 10 minutes. 50 g 50% aqueous sodium hydroxide are added. The mixture is stirred under a slow flow of nitrogen at 50-53° C. for one hour. 0.9 g anthraquinone-2,7-disulfonic acid disodium salt as catalyst is added and the reaction mixture is heated to reflux for 5 minutes. 77 g of an aqueous 19.1% by weight hydrogen peroxide solution are added into the reaction mixture with a peristaltic pump at a pumping rate of 0.4 ml/minute, whereby after 15 minutes addition time 1.6 g phthalimidomethyl-quinacridone are introduced into the reaction mixture followed by continuing the hydrogen peroxide addition while maintaining reflux and a slow nitrogen flow. The resulting red suspension is further stirred for 10 minutes at reflux then diluted with 100 ml cold water and filtered. The presscake is washed with hot water then dried, yielding a red quinacridone. The X-ray shows the diffraction pattern of a gamma quinacridone. The pigment shows outstanding pigment properties and can be applied for the red coloration of paints, inks and plastics.

Provenance & Evidence