Quinacridone mixed crystals

DPP/Quinacridone Mixed Crystal Phase ( Solid Solutions ) Pigments... 

Another phenomenon to be detected by X-ray crystallography is the formation of mixed crystals, as observed in the mixed coupling of azo pigments or the solid solutions of quinacridone pigments. A change in the angles of the reflected X-rays of a mixed crystal indicates a transition from one crystal phase to another. If, how-... 

P.O.48 mixed crystal phase with quinacridone quinone unsubstituted quinacridone maroon (golden yellow) 1... 

Quinacridone quinone itself (Sec. 3.2.1.6) is a tinctorially relatively weak yellow compound with poor lightfastness. Formation of mixed crystal phases with other quinacridones (Sec. 3.2.2) as well as treatment with various metal salts [25] leads to an improvement of light- and weatherfastness. Oxidation of dihy-droquinacridone with less than molar amounts of chromate affords a quin-acridone/quinacridone quinone mixed phase which offers an interesting shade of gold. 

P.R.206 is a mixed crystal type and consists of unsubstituted quinacridone and quinacridone quinone. The ratio between the two components as well as the crystal modification is not yet known. P.R.206 affords a very dull, yellowish shade of red, referred to as maroon. The pigment is considerably weaker than perylene pigments. All commercially available types of P.R.206 are more or less transparent and are used mostly in metallic finishes for automobiles, to which they lend reddish shades of copper. The pigment is often found to be difficult to disperse. The finishes frequently exhibit rheological problems, especially at high pigment concentration. 

A number of other members of this class are also available, although not all are listed in the Colour Index. Their exact chemical and physical properties remain to be published. The list includes mixed phase pigments made of unsubstituted quinacridone with dimethylquinacridone or other substituted quinacridones. Recently mixed crystal phase pigments of two substituted quinacridones have been published [28]. These pigments are considered specialty products for automotive finishes, especially for metallic finishes. 

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