CS195965B1 - Process for the separation of derivatives of p-phenylendiamine - Google Patents

Description

The present invention relates to a process for separating p-phenyleridiamine derivatives produced by reduction from aminoazo dyes, and is based on the use of the hydrotropic effect of reducing components intentionally previously incorporated into the starting azo dyes.

In the preparation of p-phenylenediamine derivatives by reduction of aminoazo dyes, the distribution of the final multicomponent system is associated with difficulties, as exemplified by the reduction of the dye obtained from the diazotized sulfanilic acid and p-xylidine. Sub-stages of syntheay according to the scheme:

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In addition to the cleavage components (A) 1 (B), it is also necessary to separate off the reaction mixture from the reducing agents used, such as iron oxides at work and iron, or solid catalysts employed in the hydrogen cleavage of azo dyes and the like.

The amphoteric nature of the sulfanilic acid and the baeic nature of the p-phanylandiamine derivatives, as well as their relatively low solubility in water, have hindered separation so far, regardless of the pH reduction. For example, by acidifying the reaction mixture with hydrochloric acid, sulfanilic acid is partially precipitated as a solid, and 2,5-dimethyl-p-phanylenediamine as the hydrochloride is transferred into the solution, but also a more visible sulfanilic acid portion.

After filtration and the addition of sulfuric acid to the mother liquor, a sparingly soluble 2,5-dimethyl-p-phenylenediamine sulphate is separated from most parts, but also entrains a portion of the sulfanilic acid; after separation, the mother liquors contain sulfanilic acid and the residue

2,5-dimethyl-p-phenylenediamine and their resolution is difficult.

It has now been found that the separation of p-phenylenediamine derivatives of formula I,

NH ₂

NH ₂ wherein X and Ϊ is alkyl or alkoxy each β 1-2 carbon atoms or halogen, and X and Ϊ are the same or different from the reaction mixture after reduction aminoazobarviv formula (II) (° ₃ ^H) _n - Ar η * N

(II), wherein X and I are as defined above, Ar represents a benzene or naphthalene radical, optionally containing methyl, n = 1 or 2 and e according to the invention by acting on reducing aids to azo dyes II prepared from active azo components of formula III ^(H0 3 ^S) n "'^ 2 ^<111>» NZ wherein Ar is as hereinbefore defined ahora possessing hydrotropic affect, wherein AE reduction results in an aqueous medium and the concentration of the azo dyes of 0.2 gmol / 1 solution of 0.5 gmol / 1 at pH 4 to 12 and from the reaction mixtures heated to 70 [deg.] C., optionally up to boiling, mechanically removes the products of the reducing agents and the resulting solution of the hydrotropic agent of the general formula III. and the diamine of formula I and e are cooled to crystallization and preferably to a temperature between 30 ° C to the freezing point of the system, whereupon the precipitated diamine of formula (I) is mechanically separated *

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After separation of the p-phenylenediamine derivatives of the formula I, the mother liquors are returned to the eynthesis of the aminoazo dyes of the formula II.

The new process allows to work at extremely high concentrations, which in favor of separation based on the crystallization of diamines I from the reaction solutions - favorably results in an increase in yields. A second equally significant advantage of the process of the present invention is an increase in the production capacity of the plant. The essence of the enhanced effect of the new process is the participation of reducing gases of the type (HO2Sjjj-Ar-NHg) or their salts in the formation of “supersaturated diamine solutions I after reduction *” from hot mixtures. solid iron oxides after reduction with iron or ferrous salts, or catalysts after hydrogenation).

By cooling the filtrates, most of the resulting diamines 1 can be isolated as a solid crystalline fraction. The presence of aminosulfocyeeline III salts in the process system is ensured by controlling the pH of the solutions by adjusting the pH to between 4 and 12 by adding carbonates, acetates, phosphates and other similar known ingredients; this can be done before or during the reduction or after reduction.

Example 1

To 100 ml of water was added 29 g of granular iron and 1 ml of conc. hydrochloric acid and heated to 70 ° C. This gives a slurry of etched iron for reduction.

In addition, a dye solution is prepared

by adding 61.1 g of a paste containing 0.1726 gmol of the above dye to 400 ml of water, adjusting the pH of the mixture to 7 by the addition of soda and heating the suspension to 80 ° C to form a solution. This solution, temperature of 80 ° C, is added in portions of approx. 40 ml - while stirring - to the etched iron suspension at 80 ° C. Mixing is continued for 20 minutes while the reaction mixture is decolorized (assay of the filter paper; the effluent is colorless).

At 80 ° C, the mixture was filtered and the filtrate was cooled in an ice-water bath. The precipitated coarse crystalline fraction was filtered off, washed with 60 ml of water at 5 ° C and dried. 14.3 g

2,5-dimethyl-p-phenylenediamine, i.e. 60.8% th. The mother liquors comprise practically inhaled eulfanilic acid in the form of its sodium salt and a residue of 2,5-dimethyl-p-phenylenediamine.

Example 2

5.7 L of water is poured into a 10 L stirred reactor, 300 g of azo dye as in Example 1 (i.e. 1.4124 gmol) are added and the pH of the mixture is adjusted to 10 by the addition of 30% sodium hydroxide solution. lit. stainless steel autoclave and add ee 20 g aqueous paste

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Raney nickel catalyst, followed by hydrogenation at 50 ° C and 5 atm of hydrogen over 2 hours.

After hydrogenation, the hydrogen overpressure is vented, the autoclave is heated to 90 ° C, the catalyst is allowed to settle without stirring for 20 minutes, then the reaction solution at 90 ° C is withdrawn into a closed vessel filled with nitrogen gas and cooled to crystallize and finally cool external bath ice and water at 5 ° C. The precipitated crystalline product is filtered off and washed with 300 ml of 5 ° C water containing 0.2 g of hydrosulfite.

223 wet, 77.3%, 2,5-dimethyl-p-phenylenediamine is obtained, which is 90% th. The mother liquors contain virtually all aulfanilic acid and small amounts of 2,5-dimethyl-phenylenediamine.

Claims (2)

SUBJECT OF THE INVENTION A process for separating p-phenylenediamine derivatives of the general formula (Z) nh ₂ nh ₂ wherein X and Y are alkyl or alkoxy, in each case 1 to 2 carbon atoms, or halogen, wherein X and Y are the same or different from the reaction mixtures after reduction of aminoazo dyes of formula II ( ^H ° ₃ S) _n - Ar - N - N NH2 (II), wherein X and Y are as defined above, Ar represents a benzene or naphthalenic radical, optionally containing methyl, n is 1 or 2, characterized in that aminoazo dyes of the formula II prepared from active azo components of the formula III ⁽ III ^O 3 ^S) n - Ar - NH ₂ (III), wherein n is 1 or 2 and Ar is as defined above having a hydrotropic effect, wherein the ee reduction results in an aqueous medium and a concentration of azo dyes of 0.2 gmol / l. of a solution of up to 0.5 gmol / l at pH 4 to 12 and from reaction mixtures heated to 70 ° C or to boiling point and mechanically remove the fumes from the reducing agents and the obtained aqueous solution of the hydrotropic agent of the formula III and the diamine of the formula of the formula is cooled to crystallization, preferably to a temperature of between 30 ° C and the freezing point of the system, whereupon 195 9 mechanically separates the diamine of formula (I). 2. Process according to claim 1, characterized in that the mother liquors, after separation by p-phenylenediium derivatives of the general formula I, are returned to the ayntheay eminoazo dyes of the general formula II.