Preparation method of permanent violet pigment

Abstract

The invention discloses a preparation method of a permanent violet pigment. The method comprises the following steps: dissolving 3-amino-N-ethyl carbazole in an organic solvent and carrying out a condensation reaction by adding chloranil in the presence of an acid-binding agent so as to obtain an organic solution containing 2,5-dichloro-3,6-di(9-ethyl-3-carbazole amino)-1,4-benzoquinone after the reaction; adding a metal salt catalyst into the organic solution obtained in the step a or simultaneously adding the metal salt catalyst and a quinone compound cocatalyst into the organic solution; feeding air or oxygen into a reaction kettle to reach a certain pressure; carrying out heat preservation at 120-180 DEG C for 2-10 hours; cooling to 80-120 DEG C after the reaction; washing a filter cake obtained after filtering with a small amount of organic solvent; then, respectively washing with methyl alcohol and water and drying, thereby obtaining a crude permanent violet pigment product. According to the method, a traditional poisonous and harmful closed-loop agent is not adopted, so that the cost of raw materials is saved; the generation of byproducts is reduced, so that the selectivity and total yield of the reaction are improved. Thus, less environmental pollution is generated.

Description

technical field [0001] The invention relates to a method for preparing a pigment, in particular to a method for preparing a permanent violet pigment. Background technique [0002] Permanent violet pigment is a high-grade machine pigment with dioxazine structure. As a high-grade purple organic pigment, it has outstanding coloring strength, brightness, excellent heat resistance, permeability resistance and good light fastness, and is widely used in coatings, plastics, inks, textile printing and other fields. Permanent violet pigment, see the following structure: [0003] The preparation of permanent violet pigment is based on carbazole as raw material, and the product of the above structure is obtained through the process steps of alkylation, nitration, reduction, condensation, and ring closure. At present, this method is almost used in industrial production at home and abroad (Xie Qiusheng. Yong Synthesis of Fast Violet RL and its intermediates, "Dyes and Dyeing", 2003, Vol...

AI Technical Summary

Problems solved by technology

Using aromatic ring acid chloride as a ring-closing agent will produce a large amount of by-product hydrochloric acid during the reaction, which will seriously corrode equipment and pollute the environment

In addition, the use of active aromatic ring acid chlorides results in low selectivity of the ring-closing reaction and the formation of thioether by-products (US20020091257A1), which are difficult to remove, resulting in low ring-closing yields and a large amount of waste residue

Patent EP234870 discloses the use of inorganic acids (such as hydrochloric acid, sulfuric acid) as a ring-closing agent, 2,5-dichloro-3,6-bis(9-ethyl-3-carbazole amino)-1,4-benzoquinone in React in o-dichlorobenzene at 155-160°C to obtain crude permanent violet pigment, but the reaction conversion rate is low, and the use of inorganic acid still brings equipment corrosion problems

U.S. Patent US5932727A discloses that pyridine nitrogen oxide is used as a ring-closing agent, and the ring-closing yield can reach up to 97%, but the price of the ring-closing agent is high and recovery is difficult

In addition, the use of the highly toxic substance pyridine will seriously endanger the health of employees, so it is difficult to realize industrialization