Patent Name: A method for direct production of water-soluble nigrosine

Technical Field：

The invention relates to the preparation of azine acid dyes, in particular to a method for the direct production of water-soluble nigrosine.

Background technology：

The molecular formula of water-soluble nigrosine (index number [CI]ACID BLACK 2(52420)) in azine acid dyes is C36H26O6N5S2Na (see fig. 1). the alias names of water-soluble nigrosine are acid particle element, acid particle element NBL, acid skin element NL, acid particle element green and acid black 2; The English name is = Acid nigrosine, C. I.Acid black 2, calco nigrosine 02 p>ci 50420, ci acid black 2, lurazol deep blue eb>nigrosin, nigrosine B, nigrosine wl water soluble, nigrosine wsb; Usually in particle form or powder form; Widely used in wool dyeing (in strong acid bath, PH below 3.5, adding sodium sulfate as retarding agent, in order to improve levelness), advanced ink, silk dyeing (carried out in scouring liquid, plus acetic acid or sulfuric acid to obtain gray black), leather bottom skin dyeing or leather finishing agent (pigment paste) and other fields, it is usually black granular with metallic luster or black uniform powder, soluble in water, soluble in ethanol is blue, blue in concentrated sulfuric acid, and purple precipitate after dilution; the aqueous solution was blue purple, adding sodium hydroxide was dark purple precipitation. At present, when producing water-soluble aniline black in China, it is necessary to first catalyze and condense aniline and nitrobenzene with ferric chloride, then acidify, wash, filter and dry to obtain alcohol-soluble aniline black. Then, the alcohol-soluble aniline black is sulfonated, isolated, washed, neutralized and dried to finally obtain water-soluble aniline black. The production process has long cycle, high energy consumption, each production of a ton of water-soluble aniline black needs 2. 5 tons of standard coal, heat energy waste.

SUMMARY OF THE INVENTION

In view of the defects in the prior art, the purpose of the present invention is to provide a method for directly producing water-soluble aniline black, which simplifies the process steps, shortens the process cycle, saves a lot of energy and labor resources, and reduces wastewater discharge. Greatly improve labor production efficiency. In order to achieve the above objectives, the technical scheme adopted by the present invention is a method for directly producing water-soluble nigrosine, which is characterized in that its specific steps are step 1, aniline and nitrobenzene are condensed under the catalysis of ferric chloride; Step 2, the condensed mixture is naturally cooled to room temperature; Step 3, the naturally cooled mixture is crushed and directly put into sulfuric acid for sulfonation reaction; Step 4, the sulfonated mixture is placed in cold water for isolation; step 5, the isolated mixture is subjected to solid-liquid separation and water washing, and then dehydrated; step 6, the dehydrated mixture is neutralized with sodium hydroxide or sodium carbonate; and step 7, the neutralized mixture is dried to obtain particulate water-soluble nigrosine. On the basis of the above technical scheme, the method further comprises the following step 8: pulverizing the particulate water-soluble aniline black to obtain powdery water-soluble aniline black. On the basis of the above technical solution, in step 8, the fineness of the pulverized water-soluble aniline black is less than 80 mesh. On the basis of the above technical scheme, in step 1, the temperature of the condensation reaction is controlled at 175 210°C. On the basis of the above technical scheme, in step 3, the mass ratio of the naturally cooled mixture and sulfuric acid is 1 1.8, the concentration of sulfuric acid is greater than 98%, the reaction temperature is controlled at 120 130 ° C., and the temperature is kept for 1 hour, 45 minutes and 2 hours. On the basis of the above technical scheme, in step 4, the concentration of the residual acid in the separated mixture is controlled at 18 20%. On the basis of the above technical scheme, in step 5, the terminal pH value of the water-washed mixture is 23.