CS258820B1 - Yellow azopigment and its preparation - Google Patents

Abstract

The yellow azo pigment of the general formula I, where R1 and R2 have the same or different meanings and represent an ethoxyl or amino group, is prepared by coupling a solution of the diazonium salt of a terephthalic acid derivative of the general formula II, where Ry and R2 have the above-mentioned meanings, at pH 3 to 10 and at a temperature of 0 to 30 °C with 2-hydroxy-4-methyl-5-cyano-6-pyridone of the formula III used in the form of an aqueous solution of the sodium or potassium salt or in the form of its aqueous suspension, and the obtained azo dye of the general formula I is filtered off in the cold or after heating to 80 to 90 °C, dried and mechanically treated.

Description

The present invention relates to a yellow azo pigment and a process for its preparation from terephthalic acid derivatives and substituted 2-hydroxy-6-pyridone. Similar azo pigments are used to color synthetic materials in the mass. The structure of the novel dyes according to the invention is represented by the general formula I

wherein ^R 1 ^{and R} 2 have the same or different meanings and are methoxy or amino.

The process according to the invention is characterized in that the diazonium salt of the terephthalic acid derivative of the general formula IX con.

NH,

CORj (II) where

R 1 and R ₂ are as defined above, culminating with 2-hydroxy-4-methyl-5-cyano-6-pyridone of formula III

NC.

CH,

(III)

OH

Amino compounds of the formula II are suitable

2-carbomethoxy-5-carbamoylaniline

2,5- Dicarbamoylaniline a

2,5-Dicarbmethoxyaniline (aminodimethyl terephthalate).

The process is carried out by diazotization of the amino derivatives of the terephthalic acid II with sodium nitrite and optional cleration of the resulting diazonium salt solution by addition of activated charcoal or diatomaceous earth. These are further acidified with a mineral acid, usually hydrochloric or sulfuric acid, or, in the case of aminodimethyl terephthalate, diazotization in a mere hydrochloric acid medium, at a stoichiometric ratio of 2.3 to 2.5 moles of HCl per mole of aminomethylterephthalate.

For coupling, 2-hydroxy-4-methyl-5-cyano-6-pyridone of formula III is used in the form of an aqueous solution of sodium or potassium salt, or as a suspension obtained by acidifying aqueous solutions of these salts by addition of an acid, usually hydrochloric, sulfuric / acetic acid, optionally, the suspension is prepared by grinding it in water, usually with the addition of surfactants and dispersants or protective colloids.

The actual coupling is carried out in the range of pH 3 to 10 at a temperature of 0 to 30 ° C, the dosing of the coupling components is arbitrary, so that the active component is introduced into the present passive component and vice versa, or the coupling is facilitated by adding a pH regulator such as acetate or citrate. %, or the mineral acid is blunted by the addition of neutralizing agents such as disodium carbonate or sodium bicarbonate, sodium or potassium hydroxide or calcium.

The novel azopigment prepared according to the invention is characterized by very good coloristic spreading, high thermostability and good stability in organic solvents, so that it is suitable for special applications, for example for dyeing synthetic materials in the mass or for automotive enamels. Thermostability and resistance to organic solvents are due to the nature of the substitution, since both the carbomethoxy group and the carbamoyl substituent, by their highly polar nature, contribute to the extraordinary application properties of the final azo pigment. The structure of the pyridone nucleus, which, unlike the corresponding pigment, in which the amino group of the pyridone nucleus is blocked, for example with methyl or ethyl, also has a significant influence on the formation of intermolecular hydrogen bonds and thereby favorably affects the physical properties of the pigment.

The following examples illustrate the preparation of the azo pigment according to the invention. Unless otherwise indicated, parts given in the examples refer to parts by weight.

Example 1

Dissolve 20.9 parts of aminodimethyl terephthalate in 80 parts by volume of water and 46 parts by volume of hydrochloric acid of (HCl) = 5 mol / l. A hydrochloride suspension is obtained in which, over a period of 30 to 40 minutes, 21.7 parts by volume of an aqueous solution of sodium nitrite c (NaNO4) = 5 mol / l is added so that it is still in excess, which is eliminated by addition after diazotization. urea or amidosulfonic acid. The reaction mixture is overflowed by filtration with diatomaceous earth or activated carbon and the diazo compound content is determined in the solution. The amount of the passive component used in the stoichiometric ratio or in excess of up to 2 mol% is determined by the analysis result. .

The diazonium salt solution after clerification is further coupled as such or after pH adjustment by addition of a neutralizing or buffering agent such as carbonate, hydroxide and sodium acetate, to 15.3 parts of 2-hydroxy-4-methyl-5-cyano-6-pyridone used as suspensions obtained from this salt by precipitation with acetic or hydrochloric or sulfuric acid, or the suspension is prepared by grinding solid pyridone with ballotin, or coupling is carried out with the addition of surfactants and dispersants or protective colloids, for example condensation products of ethylene oxide with higher fatty acids such as palmitic acid or stearic, and the condensation products of naphthalene sulfo acids with formaldehyde and methyl or ethyl cellulose. The resulting yellow azo pigment was isolated from the reaction mixture by filtration. The paste is dried after washing with water at 105 ° C and the dry product is ground. 33.5 parts of a pigment of formula IV are obtained

which is characterized by a pure and bright yellow hue, a high color yield, compared to pigments of superior application properties such as pigments based on condensation azo dyes. Furthermore, it is characterized by high thermostability, does not melt when heated up to 350 ° C and very good stability to common organic solvents. These properties are suitable for demanding applications, for example for dyeing plastics and for automotive enamels.

Diazotization and coupling of aminodimethyl terephthalate can also be accomplished by first dissolving the aminodimethyl terephthalate in concentrated acetic acid or N, N-dimethylformamide, acidifying the solution with hydrochloric acid or dilute sulfuric acid, and then proceeding as in Example 1.

Example 2

19.4 parts of 2-carbmethoxy-5-carbamoylaniline is diazotized and the diazonium salt is coupled with 15.3 parts of 3-cyano-4-methyl-6-hydroxy-2-pyridone as described in Example 1. After coupling, the reaction mixture is acidified by mireral acid, heated to 80 to 90 ° C, hot dye isolated, dried and mechanically treated. A yellow azopigment of formula V is obtained, characterized by practically the same application properties as the pigment prepared according to Example 1.

CH ₃ COOCH ₃

NC.

Example

Μτφ

H CONHj (A)

17.9 parts of 2,5-acarbomoylaniline are dissolved in conc. acetic acid or Ν, Ν-dimethylformamide, the solution is acidified with 50 parts by volume of hydrochloric acid c (HCl) = 5 mol / l and diazotized at 0 to 5 ° C by the addition of an equivalent of 20 parts by volume of aqueous nitrite solution sodium c (NaNop 5 mol / l) The resulting diazo compound is immediately treated by adding 15.3 parts of 2-hydroxy-4-methyl-5-cyano-6-pyridone used as an aqueous potassium salt solution, or The coupling is carried out by slowly adding sodium nitrite solution to the mixture of coupling components so that the coupling mixture is still mineral acidic, the resulting dye is isolated and mechanically treated after drying under reduced pressure to give a yellow azopigmept of formula VI of similar properties to pigments of formulas IV and V.

CH ₂ CONH ₂

NC.

(VI)

conh ₂

Claims (2)

OBJECT OF THE INVENTION 1. Azo azig-pigment of the general formula I CH, where NC ύτ ^{ν = ν} 0 ^{<! Í} | ^{Ra 'x} 0H H cor ₂ (I) have the same or different meanings and are methoxy or amino. 2. A process for the preparation of a yellow azo pigment according to claim 1, characterized in that the solution of the diazonium salt of the terephthalic acid derivative of the formula II is: COR ₁ A / ™ ² (XI) where COR ₂ R | and R ₂ is as defined above, coupled at pH 3 to 10 and at 0 to 30 ° C with 2-hydroxy-4-methyl-5-cyano-6-pyridone of formula III (III) used as an aqueous sodium solution or the potassium salt or in the form of an aqueous suspension thereof and the obtained azo dye of the formula I are filtered, dried and mechanically treated with cold or after heating to 80 DEG-90 DEG.