Research On Clean Synthesis Of Azo Disperse Dyes With Weakly Alkaline Aromatic Amines As Diazo Components

As the only suitable dye for dyeing polyester fiber, disperse dye has become the largest class of dyes required in dyeing and printing industry with the development of polyster fiber. Azo disperse dye occupys over70%of the field of disperse dye and plays an important role. The scope of its colour is mainly in the dark area of visible light, to which azo disperse dye with weakly alkaline aromatic amine as diazo component contributes much. The dosage of concentrated sulfuric acid in the process of its diazo-reaction consumes more than a dozen moles, most of those are treated with CaCl2to generate CaSO4which are buried expect2moles in theory. Although now waste sulfuric acid have been processed and resued by some factories, sulfuric acid is consumed. To solve above problems, the idea designed is to reduce the use of concentrated sulfuric acid from the source, and two methods were taken:The first one was to replace part of concentrated sulfuric acid with ionic liquids which could be recycled as solvent of diazotization reaction and were also as the solvent of coupling reaction. However, the solubility of diazo components and dye yields were respectively0.4-0.6g and50%-60%which were low. What’s worse, the ionic liquids were hardly separated from the dyes generated and used again. Therefore, this method was not desirable.The other one was to take the place of some concentrated sulfuric acid with fluoroboric acid as diazonium salt stabilizer and ethyl acetate which could also be recycled as solvent of diazotization reaction. Diazonium salt precipitated from ethyl acetate which was with excess concentrated sulfuric acid as solvent of next diazotization reaction and was coupled to synthesis dye. Dye1, Dye2, Dye3and Dye4were synthesized by respectively diazotized from2-cyano-4-nitroaniline,2,4-dinitroaniline,2-chloro-4-nitroaniline and2-cyano-4-nitro-6-brom-oaniline and coupled from3-(N,N-diethyl)amino acetanilide. The dye fields could reach and partly exceed80%-85%which is the field of conventional method. The purity was more than82%and almost higher than the one of conventional method. What’s more, the dosage of concentrated sulfuric acid which decreased to2.3-2.8moles every time significantly reduced compared with conventional method. And the consumption of fluoroboric acid was1-2moles. Ethyl acetate can be recycled for5-7times, and each time recovery rate was more than98.5%. The molechlar structures of the four dyes were characterized by1H NMR, MS, FTIR and UV-visible spectra.The dyes prepared from above and conventional methods were respectively used for dyeing polyester fiber by means of high temperature-ultrahigh pressure method. Compared with conventional method, Exhaustion of Dyel and Dye4increased by1.5%-6.7%,K/S value of four dyes changed by-4.0%-9.5%, Brightness (L*) of Dye3increased by about10%, chroma (C*) of Dye2and Dye3increased by20%-30%and hue (h*) of four dyes changed so small that it was hardly awared by human retina. The fastness to rubbing, washing fastness, sublimation fastness (180℃) and light fastness were averagely increased by0.5-1.