CS242294B3 - Method of m-aminophenylurea preparation - Google Patents

Abstract

Process for the preparation of "m-aminophenyl urea by basic MS. author's certificate No. 200,441, the essence of which is that an aqueous solution of cyanate is used for the reaction potassium stabilized by addition 0.1 to 5% by weight of hydroxide sodium and / or potassium.

Description

(54) A process for preparing m-aminophenyl urea

The process for the preparation of m-aminophenyl urea according to the basic art. No. 200,441, which is characterized in that an aqueous potassium cyanate solution stabilized by the addition of 0.1 to 5% by weight of sodium and / or potassium hydroxide is used for the reaction.

The present invention relates to a process for the preparation of m-aminophenyl urea of the formula (C ^-nh ₂ nh-co-nw ₂₎ by reacting cyanic acid with m-phenylenediamine in an aqueous-acidic medium according to AO No. 200 441. potassium cyanate, complete protonation of one and partial protonation of the other amino group of m-phenylenediamine.

The process has been used in the production of m-aminophenyl urea for many years. Usually, for practical reasons, it is carried out by adding an aqueous solution of KCNO to the acidic solution of m-phenylenediamine of acidity specified in AO No. 200 441 and maintained by adding an aqueous solution of HCl.

This method has the disadvantage of the instability of the aqueous KCNO solution, which is partially decomposed according to the equation

KCNO + 4 H 2 O = K 2 CO 3 + (NH 4) 2 CO 3

This decomposition is catalyzed by impurities in the water and apparatus and sometimes takes on considerable dimensions. Sometimes it results in a significantly higher KCNO consumption than it corresponds

KCNO i - {θ ^ ~ ΝΗ + 0Γ r ~ L

NH3C1 theory, on the one hand, higher consumption of HCl to neutralize the formed alkali carbonates. The foaming caused by the carbon dioxide resulting from this neutralization greatly slows the reaction progress and limits the production capacity. The resulting mineral salts deteriorate the crystalline form of the product, burden wastewater and can cause serious disturbances in the production of reactive dyes from prepared m-aminophenyl urea.

Disadvantages are eliminated by the process for the preparation of m-aminophenyl urea according to the invention, which comprises using a potassium cyanate solution stabilized by the addition of 0.1 to 5% by weight of sodium and / or potassium hydroxide.

This completely removes the decomposition of the initial KCNO solution, decreases its consumption, also decreases the consumption of HCl, which was previously required not only for the release of HCNO but also for neutralization of alkali carbonates, eliminates foaming during reaction, it may not need to be recrystallized, and the amount of inorganic salts in the waste water is reduced. The stability of the KCNO solution also constitutes one of the necessary prerequisites for reducing labor intensity, resp. production continualization.

In well-controlled preparation according to the invention, the consumption of KCNO HC1 and m-phenylenediamine manufacturing approaches the theoretical sum by the equation ^> - NH C ₃ F kc;

NhiCON1 · ^ although this equation does not describe the actual reaction mechanism, as explained in the AO interpretation No. 200 441. Only a very small part of KCNO is consumed during condensation by side reaction

KCNO + 2HCl + H2O = KCl + NH4Cl + CO2

The reduced amount of mineral salts formed further allows a higher concentration of the reaction mixture, i.e. an increase in feed, which in turn is now advantageous for suppressing the solubility and dissociation of the resulting m-aminophenylurea hydrochloride, thereby allowing the final pH to increase to about 2.5 increased formation of m-phenylenediurea.

He did

To a solution of 220 kg of m-phenylenediamine (2.04 mol) in 350 L of water and 360 1.32 wt. hydrochloric acid (3.8 mol) with an initial pH of about 1.2 was added at 30 ° C a solution of 170 kg (2.1 mol) KCNO and 2 kg NaOH in 265 L of water. During admission, the temperature was maintained below 30 ° C by external cooling, and dropped below 20 ° C at the end after the solution inflow slowed.

The pH of the reaction mixture slowly increased from the initial value to about 2.5, after which the gradual admission of the remaining about 30 L (0.3 mol) of HCl solution began to the total amount required for the actual condensation reaction.

The formed m-aminophenylurea hydrochloride slurry with a small amount of m-phenylenediurea (about 1% by weight) was filtered off. The yield was 293 kg of m-aminophenyl urea in the form of about 40% aqueous paste (95% of theory).

Example 2

The batch and the condensation as in Example 1. However, the m-aminophenylurea suspension after condensation was dissolved by adding NaOH solution to pH 5.5 by diluting with water to a total volume of 2400 L and heating to 60 ° C. After addition of carboraffin and diatomaceous earth, the m-aminophenylurea base solution was pre-filtered, acidified with excess HCl solution after filtration, the crystals were enlarged by brief heating to 85 ° C with immediate cooling to 25 ° C and filtered. The yield was 277 kg of m-aminophenylurea in the form of about 55% aqueous hydrochloride paste (90% of theory).

Claims (1)

SUBJECT The process for preparing m-aminophenyl urea according to U.S. Pat. No. 200,441, characterized in that an aqueous solution of potassium cyanate, stearate billated by the addition of 0.1 to 5% by weight of sodium and / or potassium hydroxide is used for the reaction.