Synthesis and Application of C.I. Pigment Orange 64
|School||East China University of Science and Technology|
|Keywords||C.I. Pigment Orange 64 5-amino-6-methylbenzimidazolone one-pot reaction aftertreatment|
C.I. Pigment Orange 64 is one of benzimidazolone pigments characterized by excellent weatherfastness and heat stability, primarily used in modulating high grade industrial finishes and coloring engineering plastics.5-amino-6-methylbenzimidazlone is the key intermediate of C.I. P.O.64. Its industrial scale production has not been well developed in our country.In the paper, a novel process of making 5-amino-6-methylbenzimidazlone was developed. We used 4-methyl-2-nitroaniline as starting material, which was reduced with hydrazine hydrate to form 3,4-diaminetoluene, then 5-methylbenzimidazolone was obtained by reacting 3,4-diaminetoluene with urea via condensation reaction. Finally,5-amino-6-methyl-benzimidazolone was synthesized by nitration of 5-methylbenzimidazolone and subsequent reduction of 5-nitro-6-methylbenzimidazolone.After optimizing the process,5-nitro-6-methylbenzimidazolone could be obtained by a one-pot technology, i.e., the condensation and ring-closure reactions between 3,4-diaminetoluene and urea and the nitration reaction between 5-methylbenzimidazolone and nitric acid could be conducted in chlorobenzene.Due to the traditional iron power reduction of 5-nitro-6-methylbenzimidazolone was not environmental-friendly, we employed hydrazine hydrate as reducing agent instead of iron powder. As a result, the reduction product could be obtained in good quality and be directly used for the production of C.I. P.0.64 without further purification. After optimizing the process, the total yield of 5-amino-6-methylbenzimidazlone is 69.5%, calculation based on 4-methyl-2-nitroaniline.C.I. P.O.64 was made by diazotization of 5-amino-6-methylbenzimidazolone and subsequent coupling of the diazonium salt with barbituric acid. The crude pigment was treated with organic solvent to adjust the pigment particle size and distribution. On the base of testing the performance, some parameters were discussed in the course of aftertreatment.