Synthesis of Electrophotographically Active Chlorodiane Blue Pigment
Original Publication Date: 1983-Nov-01
Included in the Prior Art Database: 2005-Feb-07
The novelty in this synthetic procedure is found in the interactions of certain process variables: (1) rate of addition of the reagents used to form chlorodiane blue (CDB), (2) the ratios of pyrridine-dimethylsulfoxide-dimethylformamide, (3) the reaction temperature, and (4) the isolation and purification techniques used to obtain the final product. Preparation of bis-diazo-3,3'-dichlorobenzidine bis-tetrafluoroborate is accomplished by treating an aqueous 6M HCl solution of 3,3'-dichlorobenzidine with two equivalents of nitrous acid. A fourfold excess of fluoroboric acid is then added to the cold acid solution to precipitate bis-diazo-3,3'-dichlorobenzidine as the bis-tetrafluoroborate salt. This salt is isolated by vacuum filtration and is then washed with cold methanol and subsequently with diethyl ether.