DK162761B - STABILIZED SOLUTIONS OF HYDROXYLAMINE OR SALTS THEREOF METHOD OF PREPARING THESE - Google Patents

Description

DK 162761 B

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The invention relates to stabilized solutions of hydroxylamine or its salts in water or alcohols and to a process for their preparation.

Solutions of hydroxylammonium salts decompose slowly at room temperature and more rapidly at elevated temperature. This is more true for solutions of free hydroxylamine. It has not been lacking in attempts to stabilize solutions of hydroxylamine and its salts to provide improved storage properties. According to US PS 3 544 270, urea is used in water as a stabilizing agent. It is known from US PS 3 480 391 that amidoximes are suitable as stabilizers and in US PS 3 480 392 hydroxamic acids are recommended for the same purpose. Finally, the use of chelating agents, such as the sodium salt of ethylenediamine tetraacetic acid, as a stabilizing agent is known from US PS 3 145 082. However, it is desirable to provide stabilizing agents which are more effective than those previously used.

The object of the invention is to provide stabilized solutions of hydroxylamine or its salts which are stable over a longer period of time and are particularly distinguished by a minimal decomposition of free hydroxylamine.

This object is solved according to the invention by stabilized solutions of hydroxylamine or its salts in water or alcohols, which are characterized in that they contain flavanes of formula K2 in, 2

DK 162761 B

wherein R 1 - each means a hydrogen atom, a hydroxyl group, a (C 1 -C 4) alkoxy group or a (C 1 -C 2) acyloxy group, at least one substituent being a hydroxyl group.

The invention further relates to a process for the preparation of stabilized solutions of hydroxylamine or its salts by the addition of stabilizers which are characterized by removing the molecular oxygen present in the dissolved form from the solutions desired to be stabilized by treatment with nitrogen which does not contain molecular oxygen, and then adds flavanes substituted by at least one hydroxyl group.

The stabilized solutions of hydroxylamine or its salts according to the invention have the advantage of being stable over a longer period of time than the previously known stabilized solutions. In particular, the decomposition of free hydroxylamine is reduced to a minimum.

In the preparation of the solutions according to the invention, solutions of hydroxylamine or its salts in water or alcohols are used, e.g. alkanols having 1-4 carbon atoms. Suitable hydroxylamine salts are e.g. salts with strong mineral acids such as sulfuric acid, nitric acid and hydrochloric acid, or with fatty acids, e.g. acetic or propionic acid. Due to the various solubilities, hydroxylamine is preferably dissolved in water or alcohols, while the salts are preferably present as aqueous solutions. The content of hydroxylamine or its salts usually ranges from 10 to 70% by weight. The starting solutions usually have a pH value of 8 - 11. Particularly preferred are solutions of hydroxyl amine in water.

As stabilizers, flavanes containing at least 1, preferably at least 3 hydroxyl groups, are used in the molecule.

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Preferred flavanes are compounds of the formula wherein R 1 - R 2 each means a hydrogen atom, a hydroxy 1 group, a (C 1 -C 4) alkoxy group or a (-C 2) acyloxy group, wherein at least one substituent is a hydroxyl group .

Particularly preferred flavanes of formula (I) are compounds wherein R 1 - R 2 each represent a hydrogen atom, a hydroxyl group or a methoxy group, with at least 3 substituents being hydroxyl groups. The hydroxy-substituted flavanes may also be present as glycosides.

Suitable flavors are known from Angewandte Chemie _68 (1956), pages 110 and 111.

The hydroxy-substituted flavanes are preferably used in an amount of from 0.005 to 1% by weight, in particular from 0.01 to 0.1% by weight, based on the solution desired to be stabilized. Furthermore, it has been found advantageous to reverse polyhydroxybenzenes, especially pyrogallol. The polyhydroxybenzenes are preferably added in amounts of 0.005 to 0.1% by weight, based on the solution desired to be stabilized. It is noteworthy that a synergistic effect is produced by the combined use of hydroxyl-substituted flavanes and polyhydroxybenzenes.

Stabilized solutions of hydroxylamine or its salts in water or alcohols are prepared according to the invention in the following way: first, the dissolved molecular oxygen present in the solutions which are desired to be stabilized is displaced by treatment with nitrogen which does not contain molecular oxygen. This treatment

DK 162761B

4 ling can e.g. is carried out by passing oxygen-free nitrogen, e.g. for 5 - 10 minutes. The nitrogen used preferably contains less than 2 ppm O

Thereafter, hydroxy-substituted flavan and optionally polyhydroxybenzenes are added and dissolved in the solution which is desired to be stabilized. This is preferably done at a temperature of 5 - 40 ° C. It is also possible to add the stabilizers in the dissolved state, e.g. dissolved in alkanols having 1-4 carbon atoms.

Obviously, it is advantageous to avoid contamination of the solutions with heavy metals, especially copper or precious metals, as these catalyze the decomposition of hydroxylamine. Furthermore, it is advantageous to exclude energy-rich rays by using suitable colored glass containers. Finally, it is advantageous to store the stabilized solutions at temperatures less than 40 ° C, e.g. at temperatures of 5 - 20 ° C.

The stabilized solutions of hydroxylamine or its salts are suitable for the production of oxymers. In the following, the invention is further illustrated by way of example.

EXAMPLE

An aqueous solution of hydroxylamine was treated with 25 oxygen-free nitrogen for 10 minutes at 20 ° C, after which the stabilizer was added. Hydroxylamine concentration, amount and type of stabilizer added, as well as the time and temperature dependent results are shown in the table below.

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DK 162761 B

TABLE

Stabilizer * C

50 ppm d-Catechin 5 0 743 1198 hours

110.88 110.72 110.55 g / l NH 2 OH

50 ppm d-Catechin 20 0 404 1195 hours

110.25 109.63 109.49 g / l NH 2 OH

50 ppm d-Catechin 40 0 359 1194 hours 110.25 109.79 108.57 g / l NH

Claims (5)

1. Stabilized solutions of hydroxylamine or its salts in water or alcohols, characterized in that they contain as a stabilizing agent flavanes of formula R 2 R 5 wherein R 2 - each means a hydrogen atom, a hydroxyl group, a (C alkoxy group or a (C 1 -C 4) acyloxy group, at least one substituent being a hydroxy group. Stabilized solutions according to claim 1, characterized in that they contain flavanes of the formula as set forth in claim 1, wherein - R 1 is each a hydrogen atom, a hydroxy group or a methoxy group, at least 3 substituents being hydroxyl groups. Stabilized solutions according to claims 1 and 2, characterized in that they contain 0.005 - 1 weight-15 flavans of formula (I), calculated on the solution desired to be stabilized. Stabilized solutions according to claims 1-3, characterized in that they additionally contain pyrogallol. Process for the preparation of stabilized solutions of hydroxylamine or its salts in water or alcohols by the addition of stabilizers, characterized in that the molecular oxygen present in the dissolved form is removed from the solutions desired to be stabilized by treatment with nitrogen which does not contain molecular oxygen and then adds hydroxy-substituted flavanes.