CS267458B1 - Process for preparing m-aminophenyl urea - Google Patents

Abstract

The solution relates to a method for producing maminophenylurea by reacting m-phenylenediamine hydrochloride with potassium cyanate in a hydrochloric acid medium with a pH of 1.3 to 1.6 or in a buffered medium of ammonium chloride and hydrochloric acid in the presence of organic complexing agents, for example sodium salt of N,N -bis-2-hydroxyethylaminoacetic acid in an amount of 0.2 to 0.3 kg of a 40% aqueous solution per 100 g of m-phenylenediamine. These substances inactivate the metals present in the raw materials, so that the formation of guanidine derivatives, which are undesirable both from the point of view of technology and product quality, is completely suppressed.

Description

The invention relates to a process for the preparation of m-amino-phenylurea by reacting m-phenylenediamine hydrochloride with potassium cyanate at pH 1.3 to 1.6 or in a buffered medium of ammonium chloride and hydrochloric acid in the presence of organic complexing agents.

In the current process for the production of m-amino-phenylurea, which is based on technical grade raw materials commonly processed in the chemical industry, in addition to the desired reaction accompanied by a side reaction to form m-phenylenediurea, subsequent reactions are formed in which guanidines are formed according to the following equations 1 a 2:

NH.CO.NHg

KCUO + 2HCl

/ 1 / ₊ 2 C0 ₂ 4- 2KC1

The described guanidine derivatives, i.e. m-aminophenylguanidine and m-phenylenediguanidine, are their own. completely undesirable properties in the product, as they degrade its quality, which is also reflected in the technology of production of m-aminophenylurea.

Reactions (1) and (2) are catalyzed by certain metal ions, in addition to alkaline and corrosive earth metal ions, which are always present in trace amounts in the raw materials. In the acidic environment in which the main reaction takes place, these ions are activated and cause the formation of guanidines as a result of subsequent reactions (1) and (2).

The process for the preparation of m-aminophenyl urea by reacting m-phenylenediamine hydrochloride with potassium cyanate in an acidic medium, which is the subject of the invention and which consists in the presence of organic complexes, eliminates these disadvantages. forming agents, for example the sodium salt of N, N-bis-2-hydroxyethylaminoacetic acid in an amount of 0.2 to 3 kg of a 40% aqueous solution per 100 kg of m-phenylenediamine, preferably 0.6 to 1.65 kg of a 40% aqueous solution per 100 kg of m-phenylenediamine. The formation of undesired guanidines is completely suppressed by the process according to the invention, since the complexing agents act as inhibitors of the catalytically active metal ions present. Some aminoacetic acid compounds can be used, for example the sodium salt of N, N-bis-2-hydroxyethylaminoacetic acid. The choice of complexing agents is not limited to said aminoacetic acid derivative, which is the most suitable in the present case and is also commercially available. Other complexones with similar properties can be used.

To further illustrate the invention, the following examples are given:

Example 1

350 l of water are introduced into the enamelled boiler and 260 kg of m-phenylenedi are introduced through a hopper

CS 267 458 Bl amine. After dissolution, 360 l of 32% hydrochloric acid are allowed to stir with stirring and a solution of potassium cyanate (215 kg of 95% of potassium cyanate dissolved in 380 l of water) is added at 3 to 4 hours with the addition of 2.2 kg of 40 % aqueous solution of sodium salt of N, N-bis-2-hydroxyethylaminoacetic acid. During the reaction, the pH of the reaction mixture is maintained at 1.3 to 1.6 by co-impregnation with 32% hydrochloric acid. After impregnation of all the potassium cyanate solution, the reaction is complete after stirring for 0.5 hours. 130 l of 45% sodium hydroxide are then added to the reaction mixture, which is made up to volume with water. volume 2,400 l, heated to 65 DEG C. and, after the addition of 5 kg of filter aid, is passed through a calolis and the clear clerate is acidified with 360 l of 32% hydrochloric acid. After cooling to 25 [deg.] C., the precipitated m-aminophenylurea is filtered off with suction.

The yield is 312 kg of 100% m-aminophenylurea, 86% of theory for m-phenylenediamine.

Example 2

To a solution of 260 kg of m-phenylenediamine in 950 l of water, 530 l of 36.7% hydrochloric acid are admitted in an enamelled kettle and 00 kg of ammonium chloride are added. After cooling the reaction mixture to -6 ° C to -4 ° C, a solution of potassium cyanate (245 kg of 95% potassium cyanate dissolved in 400 l of water) containing 1.95 kg of a 40% aqueous solution of sodium salt of N, N - bis-2-hydroxyethylaminoacetic acid. The temperature rises to 0 ° C to 5 ° C during the reaction and is gently cooled with a brine bath. After admitting the potassium cyanate solution, the reaction mixture is stirred for a further 2 to 3 hours at the same temperature to react the cyanic acid, then 350 l of water are added, the mixture is stirred for a further 0.5 to 1 hour without cooling and the precipitated m-aminophenylurea is filtered off. .

The yield is 319 kg of 100% m-aminophenylurea, 88% of theory for m-phenylenediamine.

Claims (1)

Process for the preparation of m-aminophenylurea by the reaction of m-phenylenediamine hydrochloride with potassium cyanate in an acidic medium, characterized in that the reaction is carried out in the presence of organic complexing agents, for example sodium N, N-bis-2-hydroxyethyl 1-aminoacetic acid 2 to 3 kg of a 40% aqueous solution per 100 kg of m-phenylenediamine, preferably 0.6 to 1.65 kg of a 40% aqueous solution per 100 kg of m-phenylenediamine.