CS198045B1 - Method of preparing water insoluble azo dyes - Google Patents

Description

The present invention relates to the use of surfactants in the preparation of water-insoluble azo dyes by means of which couplings in the environment can be carried out. where the reactions do not take place or proceed in a very limited manner.

The patent literature describes methods of using cationic active substances in the coupling, in an amount of 1 to 10 56, preferably 1 to 3%, which affect the coloretic properties of the pigment or its yield. Aliphatic amines having a carbon chain of C18 to _C18 , acid amides, secondary, tertiary amines with long polyoxyethylene chains and other substances are used. These are added to the reaction of the mixture during diazotization or to a solution or suspension prior to coupling.

We have now found a process for the preparation of water-insoluble azo dyes based on naphthols, 3-hydroxy 2-naphthoic acid arylides and acetoacetate acetic acid aids which comprises adding to the reaction of the mixture in the coupling reaction no more than 0.9 % by weight of pigment. The cationic compositions cannot be dosed arbitrarily, since there is a direct relationship between the amount of cationic agent (calculated on the weight of the pigment) and the spreading rate of the pigment.

If the reaction mixture contains above 1% of these auxiliaries, very small optically inactive particles are formed and, as a result, reduced pigment yield.

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This is particularly noticeable for water-insoluble azo dyes prepared by coupling and naphthols, 3-oxy-2-naphthoic acid arylides and acetoacetacetic acid arylides. However, if a cationic agent such as an ethylene oxide secondary amine and a longer carbon chain is used in an amount of 0.3 to 0.9% by weight of the pigment, the coupling of the respective diazonium salts with the above passive components is suspended in a slightly acidic medium with an almost quantitative yield and the dye obtained shows good coloretic properties.

An advantage of a process in which cationic substances are added to the reaction mixture during coupling is the possibility of using a higher concentration of reacting components. This factor is of particular importance in production, when ae achieves an increase in reactor volume unit performance. The pigment prepared in this way is perfectly filterable and also its coloretic properties are superior to that of the coupling, if any, in the absence of these substances.

The following examples illustrate embodiments of the process for preparing the water-insoluble azo dyes according to the invention. Unless otherwise stated, parts are by weight in all cases.

Example 1

Prepare a solution of the diazonium salt from 15.2 d. Of 4-nitro-2-aminotoluene, which is coupled with the prepared suspension of 29.7 d. Of 3-hydroxy-2-naphthoic acid 4-chloroanilide, to which 0 is added before the diazolate solution is added. , 34 d. Ethylene oxide octadeeylamine. Couples ee at 50% and pH 4.5-5.5 20 min. The resulting dye is filtered, washed and dried. 45.1 d of dry red dye are obtained.

Example 2

The 2,5-dichloroaniline is diazotized and the resulting solution is coupled with the prepared suspension of 26.3 d. Of 3-hydroxy-2-aftoic anilide with the addition of 0.32 d. Of ethylenoxidized octadeeylamine. Couples ee at 60 ° C and pH 4.5 for 20 min. The resulting dye suspension is filtered, washed and dried. The yield of red pigment is 42.8 d.

Claims (2)

SUBJECT OF THE INVENTION A process for the preparation of water-insoluble azo dyes based on naphthol, acid arylides 3-Hydroxy-2-naphthoic acid and acetothioethoetic acid arylide, characterized in that cationic substances are added to the reaction mixture in the amount of not more than 0.9% by weight of the pigment during the coupling.