CS237748B1 - Process for the preparation of 1-diazo-2-naphthol-6-nitro-4-sulfocyanaline ammonium salt - Google Patents

Abstract

A method for preparing the ammonium salt of 1-diazo-2-naphthol-6-nitro-4-sulfonic acid of the formula by nitration of 1-diazo-2-naphthol-4-sulfonic acid in such a way that the starting material is converted into an aqueous solution containing 0.7 to 1.3 mol. of free 1-diazo-2-naphthol-6-nitro-4-sulfonic acid, the resulting solution is neutralized with gaseous ammonia, or its concentrated aqueous solution to a pH value of 2.3 to 5.7, the ammonium salt of 1-diazo-2-naphthol-6-nitro-4-sulfonic acid is isolated from the reaction mixture by filtration and the mother liquors are optionally used for a further purification cycle.

Description

The present invention provides a process for the preparation of the ammonium salt of 1-diazo-2-naphthol-6-nitro-4-sulfonic acid.

The ammonium salt of 1-diazo-2-aaftol-6-nitro-4-sulfoacid produced by nitracyl-1-diethoxy-2-naphthol-4-sulfoacid has utility for the preparation of mordant or metalocomplete dyes. The industrially produced 1-diazo-2-nef tol-6-nitro-4-aulfokyoelina is accompanied by a series of undesirable side-products which, in the course of a longer processing time, significantly deteriorate the hue quality and the etoethane of synthesized dyes.

For these reasons, a massioperative insulation is usually required during preparation, which, in addition to the loss products, also causes other problems.

It has now been found that the removal of undesirable balate substances is substantially more effective, i.e. without the need for less effective isolation at the dye stage, and occurs when a high purity ammonium salt of 1-diazo-2-naphthol-6-nitro-4 - sulfoacids prepared by neutralizing the crude free acid with ammonia in an aqueous medium.

A process for the preparation of the ammonium salt of 1-diazo-2-naphthol-6-nitro-4-sulfonic acid of the formula

According to the invention, the nitro-1-diazo-2-naphthol-4-sulfo-acid is based on the fact that the starting material converts into an aqueous solution from a content of free 1-diazo-2-naphthol-6-nitro-4-sulfoacid of 0.7 to 1; 3 mol.dm-3, the resulting solution is neutralized with ammonia gas or a concentrated aqueous solution thereof to a pH of 2.3 to 5.7, 1-diazo-2-naphthol-6-nitro-4-sulfo-acidic ammonium salt the mixture is isolated by filtration and the mother liquors are optionally used for further purification process.

In this way, a high purity raw material suitable for preparing the aforementioned dyes is obtained in a yield of 80% to 95%, and as mentioned, the mother liquors can advantageously be re-used for the next purification cycle, thereby increasing the yield of the purification process. T '

The method of purification of 1-diazo-2-naphthol-6-nitro-4-sulfonic acid according to the invention is described in more detail by the following non-limiting example.

Example

500 kg of crude paste containing 65% free 1-diazo-2-naphthol-6-nitro-4-sulfoacidine was dissolved in 200 diP of water at 16 to 23 ° C with stirring and the resulting solution was treated with concentrated ammonia solution. in such an amount as to obtain a final pH of 3.5, at which time also a pale yellow crystalline substance corresponding to the ammonium salt of 1-diazo-2-naphthol-6-nitro-4-sulfocyanel also starts to precipitate from the reaction. The resulting suspension was stirred for up to 1 hour, after which time the crystalline product was collected by filtration.

The filtrate containing 8% of 1-diazo-2-naphthol-6-nitro-4-sulfonyl acid salt in addition to the dissolved balate admixtures can be used to dissolve another batch of feedstock, the number of cycles being limited by the starting and desired quality of 1-diazo-2- naphthol-6-nitro-4-sulfonyl acids, respectively. its ammonium salts.

Claims (1)

SUBJECT OF THE INVENTION A process for the preparation of the ammonium salt of -dizo-2-naphtol-6-nitro-4-sulfoacids of the formula nitro-1-pyrazole-2-naphthol-4-sulfo-acid, characterized in that the starting material is converted into an aqueous solution and 2-Naphthol-6-nitro-4-sulfoalkyls 0.7 and S The resulting solution is neutralized with gaseous ammonia or its concentrated aqueous solution to a pH of 2.3 to 5.7, ammonium salt, dlazo-2-naphthalene-6-nitro-4. the sulfo acids are isolated from the reaction mixture by filtration and mother liquors and optionally used for the next purification cycle.