CS252919B1 - Process for preparing stabilized arendiazonium salts - Google Patents

Abstract

A method for preparing stabilized arendiazonium salts, especially arendiazonium chlorozincate, by nitrosation and subsequent diazotization of the starting amine in the presence of HCl and zinc dust, in which tartaric acid is added to the diazonium salt solution in an amount of 3 to 20% by volume of the reaction slurry before isolation by salting out with sodium chloride, and the precipitated product is filtered off with suction and

Description

(54)

Process for the preparation of stabilized arendiazonium salts

Process for the preparation of stabilized arendiazonium salts, in particular arendiazonium chloride zinc by nitrosation and subsequent diazotization of the starting amine in the presence of HCl and zinc dust, by adding tartaric acid in an amount of 3 to 20% per volume of reaction slurry to the diazonium salt solution prior to isolation; aspirated to the desired active substance content.

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The invention relates to the preparation of stabilized arendiazonium, in particular arendiazonium chloride zincates, by adding a larger amount of tartaric, citric or similar solid organic acids to the solution before isolation of the substance.

The stabilized diazonium salt is intended for use in solution together with a passive component and other excipients for glazing suitable substrates in the manufacture of diazographic materials.

□ For a long time, many diazonium salts stabilized as chlorzincates have been produced industrially and supplied as a dry substance, sometimes filled with various inorganic or organic salts for safety reasons. At the same time, drying or filling is the most demanding part of the technology in terms of energy, time and risk. The diazonium salts used are in most cases p-phenylenediamine derivatives, differently substituted on the nitrogen at the p-position to the diazo group and also differently substituted on the benzene ring. They are used in reprography for the production of diazographic materials, for the production of offset plates, for the right of light-sensitive varnishes, etc. The stabilized diazonium salts thus prepared must be stored in cold places, protected from elevated temperature and impact as they decompose sharply at elevated temperature. Occasionally accidents occur during production.

It has now been found that, after diazotization of the starting amine, sufficient tartaric acid or other solid organic acid such as citric acid and the like is added prior to salting out before salting out. the diazonium salt is separated in a more suitable form for isolation and after filtering the cake to the desired dry matter, the paste can be stored for a long time without drying. The process for the preparation of stabilized arendiazonium salts, in particular arendiazonium chloride zincates by nitration and subsequent diazotization of the starting amine in the presence of HCl and zinc dust, according to the invention, consists in adding to the diazonium solution

252,919 of the salt prior to isolation by salting with sodium chloride is added tartaric acid in an amount of 3 to 20% per volume of reaction slurry and the precipitated product is aspirated to the desired active substance content. After one year of storage under normal conditions, the active substance loss is only a few tenths of a percent.

The examples below limit, but do not limit, the invention.

Example 1

4.41 hydrochloric acid conc., 2.7 kg of ice and 2.3 kg of N, N-diethylaniline were charged to the stirred and cooled reactor.

A solution of 1.1 kg of sodium nitrite dissolved in 2 l of water was added from external cooling over about 2 hours. The temperature was maintained between 5 and 10 ° C. About 4 kg of ice was gradually added to the cooling. During the reaction, fine brown crystals of nitro compounds begin to precipitate. The reaction slurry was allowed to stir for 1 h. Then 8.5 liters of hydrochloric acid conc., Kg of ice were added, and 2.2 kg of zinc dust was slowly added to bring the temperature between 30 and 40 ° C. After the reduction was complete, the solution was sclerified, cooled to 5 ° C, and diazotized with 0.9 kg of sodium nitrite dissolved in 2 L of water. After addition of 0.2 kg of tartaric acid, the diazonium salt was precipitated by successive addition of 3 kg of sodium chloride. After stirring, it was isolated by filtration and washed with 20% sodium chloride solution with 10% tartaric acid.

The isolated paste contains 65-80% of the active ingredient in a yield of about 70% of theory, according to the isolation method. After one year of storage under normal conditions, the active substance content did not decrease by more than 0.2%.

Example 2

2.2 kg of Ν, Ν-dimethylLaniline were processed according to Example 1. The yield was 70-75% of the theory at about 70% of the active substance in the paste.

Example 3

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2.4 kg of N-ethyl-N-hydroxyethylaniline were treated according to Example 1. The yield was 66-75% of the theory at a content of about 75% of active ingredient in the paste.

Claims (1)

SUBJECT OF THE INVENTION Process for the preparation of stabilized arendiazonium salts, in particular arendiazonium chloride zinc by nitrosation and subsequent diazotization of the starting amine in the presence of HCl and zinc dust, characterized in that tartaric acid is added to the diazonium salt solution prior to isolation with sodium chloride. the product is aspirated to the desired active substance content. Printed by Moravian Printing Works,