CS198863B1 - Azo dyes having p-xylidine radical in the molecule and method for preparing them - Google Patents

Description

The invention relates to water-soluble dyes of the general formula I, CH,

Y = N = N

NH = CH ₂ SO ₃ Me (I) wherein A denotes a benzene or naphthalenic radical bearing optionally one or two sulfo groups, optionally methyl and Me denotes a monovalent cation and a process for their preparation from CH,

CHNH CH

SO 2 Me and conventional benzenic and naphthalenic components.

Dyes of similar types are used for dyeing animal fibers and polyamides. According to the invention, the process for the preparation of azo dyes consists in reacting with known active azo components of the formula A - N ⁺ = N, where A is as defined above,

CH ₃

198 863

198 883 wherein Ue is as defined above.

Among the active components, benzenic and naphthalenic derivatives, such as aniline, toluidines, naphthylamines, aniline sulfonic acid, toluidine sulfonic acid, naphthylamine sulfonic acid, aniline disulfonic acid and naphthylamine disulfonic acid, are suitable for the novel dyes.

Compounds of formula II

wherein Ue is as defined above and denotes, for example, Na @ ⁺ , K @ ⁺ , NH4, and is prepared from xylidine, formaldehyde and acid sulfites, for example according to the author's certificate 193 133. The diazotization of said active components is carried out according to known methods. (References: Methoden der organiachen Chemie / Houben - Weyl / 4th revision, Georg Thyems Verlag Stuttgart). Coupling is accomplished by mixing the diazonium compounds and the passive components of Formula II in an aqueous medium at temperatures of 0 to 50 ° C. In the case of the use of diazonium compounds derived from aniline, toluidines and naphthylamines, the reaction is carried out in the low temperature range.

To assess the technical benefit, the preparation of new dyes can be compared to the synthesis of dyes using unsubstituted p-xylidine.

In the process according to the invention, the azo dye is formed considerably faster since the compounds of the formula II are considerably more soluble in water than p-xylidine.

The new process does not produce so-called pre-azotation, which eliminates the formation of undesirable by-products and does not lead to a reduction in yields. The discussed phenomenon can be illustrated in the case of reaction of diazotized aulfanilic acid with p-xylidine.

Besides the main reaction (1)

About --Mjl -i @

ZVe / V aw ₂ ch ₃ reaction (2):

and a priazene of the resulting priazene

198 86

<* λ ϊ® and the cleavage of the above diazoamino compound

to form the diazonium compound p-xylidine and it couples in the reaction medium with p-xylidine to form a dye of formula

N - N - () * -

CH ₃

This not only removes p-xylidine from the process and reduces the yield, but the dye p-xylidine-p-xylidine will undoubtedly be toxic and impair work hygiene.

The rate of coupling with the compounds of formula (II) is almost independent of the pH of the reaction medium, which is another significant advantage of the novel process, since it is possible to work in alkaline regions where higher component solubility and higher temperatures occur.

Based on these findings, the new process can be conveniently and easily continualized. The novel dyes can be used as such in dyeing animal fibers and polyamides. The compound of formula (II) can be cleaved off in an acidic medium to form dyes

CHs

A -Nb N ch ₃ wherein A is as defined above. The dyes do not contain impurities, which is of great importance in technical practice, and from this point of view this indirect method may be more advantageous than the schematically simpler process from p-xylidine.

The examples below illustrate embodiments of the invention.

Example 1

43.3 g of sulfanilic acid are mixed with 200 ml of water at 20 ° C, 10 g of solid NaOH are added and stirred until dissolved. The solution is acidified with 75 ml of concentrated HCl and after cooling

040 ml mixture weighing 1110 g, which contained 0.2375 gmol Azov * // ^NHCHiS ° ^{3Na> coa 95} * ^th 'as an impurity present in a small amount of dye of formula

198 883 at 10 [deg.] C. and a solution prepared from 17.25 g of NaNO2 and 100 ml of water is added in a thin stream. A suspension of the diazonium salt of sulfanilic acid in water is obtained, to which 37 g of fused sodium acetate is added with an aqueous solution prepared from 50 ml of water.

In another reaction vessel, 27.6 g of 96% sodium pyrosulphite was mixed with 40 ml of water, followed by the addition of 22.2 g of 37.8% formalin with stirring. The temperature rises spontaneously from 20 ° C to 35 ° C;

then the external bath is heated to 70 ° C and 30.3 g of p-xylidine - is added, the temperature drops to 55 ° C and an emulsion is formed. Within 10 minutes, the contents of the reactor were heated to 73 ° C, where after a few minutes the emulsion turned into a clear solution. 230 ml of water and 27.9 g of sodium bicarbonate were added and cooled to 5 ° C. To this mixture, under stirring at 5 ° C, a suspension of diazotized sulfanilic acid is added over 2 minutes, immediately forming a yellow-brown azo dye, then stirred for 2 hours and the temperature is allowed to rise to 20 ° C.

1 dye of the formula is obtained

It fell

Example 2

43.7 g of 99% methanilic acid were precipitated in the same manner as the sulfanilic acid in Example 1.

In addition, a solution of the sulphomethylated p-xylidine potassium salt was prepared from 31.6 g of 98.5. % of potassium pyrosulphite analogous to the sodium salt in Example 1.

The entire procedure was identical to that described in Example 1. The yield of the desired azo dye was 96.3% th.

Example 3

58.3 g of 99.2% naphthionic acid aa is diazotized in the same manner as in Example 1. The baits of this aa prepare the sulfomethylated p-xylidine sodium salt as in Example 1 and perform aa analogous coupling.

The reaction mixture is obtained in which the azo dye of formula (*) is contained

N * _s by $ ₃ -ζ (^ - NN

oy NH CH ₂ SO ₃ No

Hs ▼ and a yield of 93.7% th.

198 963

Claims (2)

1. A water-soluble azo dye having a p-xylidine residue in a molecule of formula I, And -N ^ N - / q \ - NM - CH _Z S0 ₃ CH ₃ RTE wherein A is the radical of benzene, naphthalene or toluene, optionally bearing one or two sulfo groups, Me is a monovalent cation. 2. A process for the preparation of dyes of the formula I, characterized in that, with the known active azo components of the formula A - N ⁺ = N, where A is as defined above, in passive azo components of the general formula at 0 DEG C. to 50 DEG C. of formula II, O. NH - CH ₂ CH ₃ rte CH ₃ wherein Me is as defined above.