CZ288713B6 - Process for preparing isoindoline pigments - Google Patents

Abstract

In the present invention there is disclosed a process for preparing isoindoline pigments of the general formula V, in which R represents hydrogen, methyl, ethyl or phenyl group by a two-stage reaction of phthalodinitrile with barbituric acid or derivatives thereof. The proposed preparation process is characterized by reacting in the first stage phthalodinitrile in an inert organic medium that is miscible with water with barbituric acid sodium or potassium salt or derivatives thereof of the general formula VI, wherein R is as specified above in molar ration 1 : 1 at pH value in the range from 8 to 14 and at a temperature ranging from 0 to 80 degC and the obtained monocondensate of the general formula VII, wherein R is as specified above is then reacted in the second stage with excess of barbituric acid or specified derivatives thereof in the presence of water and at pH value ranging from 0.1 to 6.

Description

Process for the preparation of isoindoline pigments

Technical field

The invention relates to a process for the preparation of isoindoline pigments which are used for coloring paints, plastics and printing inks.

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BACKGROUND OF THE INVENTION

Prior art processes for the preparation of isoindoline pigments consist in the separate preparation of an isoindolenine-based intermediate, which is then condensed with barbituric acid or its derivatives. German patent 20 041 999 generally describes the preparation of diiminoisoindoline 15 with CH-acids, another patent 2,628,409 mentions the preparation of the diiminoisoindoline of formula I or

II by reacting phthalodinitrile with ammonia gas in ethylene glycol. According to another German patent 3,022,839, barbituric acid condenses with isoindolenine derivatives of formula III formed by the condensation of phthalodinitrile with skyanamide or its derivatives. According to EP 424759, the phthalodinitrile is condensed with the dimethoxyiminoisoindoline IV.

The subsequent preparation of the pigment is identical and consists in the condensation of the obtained intermediates I to IV with barbituric acid or its derivatives to form a yellow pigment, which takes place mostly in an aqueous medium, resp. in a mixture of water and an organic solvent. It is the solvent used in the preparation of the compounds I to IV as the reaction medium, since they are not isolated according to the processes described. In order to condense with barbituric acid, the reaction mixture must be heated and the pH of the reaction slurry maintained between 1 and 6 by the addition of organic or mineral acids. A disadvantage of the known methods is the relatively complex process which requires separate preparation of intermediates I, II, III or IV.

SUMMARY OF THE INVENTION

These disadvantages are overcome by the process for preparing the isoindoline pigments of formula V

-1 CZ 288713 B6

wherein R is hydrogen, methyl; Ethyl or phenyl group according to the invention, characterized in that in a first step in a medium of an inert organic solvent miscible with water, phthalodinitrile is reacted with the sodium or potassium salt of barbituric acid or its derivatives of the general formula VI

(VD, where R is as defined above and Me is Na or K, in a molar ratio of 1: 1 at pH 8 to 14 and a temperature of 0 to 80 ° C and the monocondensate of formula VII formed

Wherein R and Me are as defined above, react in a second step with a 1.01 to 1.5 molar excess of barbituric acid or said derivatives thereof at a pH of 0.1 to 6 in the presence of water in a ratio of 25 to 500% by weight %, based on the organic solvent. The condensation of phthalodinitrile with the sodium or potassium salt of barbituric acid is readily carried out in an organic solvent environment at temperatures ranging from 0 to 80 ° C by stirring for 1 to 8 hours at pH 8 to 14. Water-miscible solvents inert to the reaction components , such as dioxane, glycols, glycol ethers such as ethylene glycol dimethyl ether, formamide, dimethylformamide, N-methylpyrrolidone or dimethylsulfoxide. Particularly suitable aliphatic alcohols are C] to C _6, e.g., methanol, ethanol, propanol, isopropanol, butanol, glycols such as ethylene glycol or alkyl ethers thereof, such as e.g. ethylene glycol monoethyl ether or Ethylen. The sodium or potassium salt of barbituric acid is prepared by reacting barbituric acid with a strong base such as sodium hydroxide, potassium hydroxide, or with alkali metal alcoholates such as sodium methylate, sodium ethylate or, for example, potassium tert-butylate. As the reaction medium for forming the barbituric acid salt, some of the above-mentioned water-miscible organic solvent is used, which is also the reaction medium for the reaction of the barbituric acid salt with phthalodinitrile. The reaction intermediate is not isolated but is reacted with another equivalent of barbituric acid or derivatives thereof, optionally with an excess of barbituric acid up to 120% of theory, in the same reaction medium in which it was formed. In order for the components to react, the pH of the reaction mixture must be adjusted by the addition of an organic or inorganic acid, or a mixture thereof, and the suspension heated to 20 to 100 ° C for 3 to 24 hours. As inorganic acids, hydrochloric, sulfuric or phosphoric acids can be used to adjust the pH to 0.1 to 6.0. Suitable organic acids are, in particular, formic acid, acetic acid, propionic acid, benzoic acid or terephthalic acid. In addition to the acidic environment, the effective conducting of the second condensation with barbituric acid or its derivatives also requires the presence of water in the reaction mixture in a ratio of 25 to 500% by weight, based on the organic solvent used. The required water is added to the reaction mixture either by using dilute mineral or organic acids, or it can be supplied separately before the reaction is started. When a barbituric acid derivative other than that used for its preparation is used for the condensation with intermediate VI, asymmetric pigments of the general formula V are obtained.

Pigments are used for dyeing paints, plastics and printing inks, and different levels of opacity, transparency, stability to solvents, solvents and migration are required for these different uses. These properties, which are related to the particle size of the pigment and to the particle size distribution, respectively. with their surface treatment, they can be partially influenced by the reaction conditions during the synthesis. In addition to changing the temperature, reaction time or reaction component ratio, it is mainly the presence of surfactants. Another possibility to prepare a pigment of optimal particle size is to heat it in water or in organic solvents under pressure, optionally also in the presence of surfactants. This post-conditioning should be used when the pigment as obtained in the synthesis does not have the optimum properties for the intended purpose, especially if it is too transparent in coloring.

Examples

Example 1

12.8 g of barbituric acid are introduced into 100 ml of methanol, 18 g of 30% sodium methoxide are added to the suspension and heated at 50 ° C for 30 minutes. To the suspension of sodium barbituric acid is added 12.9 g of phthalodinitrile and stirred at room temperature for 4 hours. 14.5 g of barbituric acid, 15 g of benzoic acid are added to the resulting yellow monocondensate suspension, the reaction mixture is diluted with a mixture of 240 ml of water and 10 ml of concentrated hydrochloric acid and stirred at room temperature for 3 hours. The condensation is completed by heating at 80 ° C for 18 hours during

Wherein the methanol is distilled off from the reaction mixture. The pigment is filtered hot and washed with boiling water. 31.5 g of a yellow pigment are thus obtained.

Example 2

Example 1 was followed with the following changes: 4.1 g sodium hydroxide was used instead of sodium methoxide and the reaction mixture was stirred at 40 ° C for 2 hours. Finally, 29.8 g of a brilliant yellow pigment suitable for coloring plastics is obtained.

Example 3

Example 1 was followed with the following changes: 100 ml of 15 ethylene glycol monomethyl ether was used instead of methanol, the monocondensate was prepared at 50 ° C for 2 hours.

The ethylene glycol monomethyl ether was not distilled off from the reaction mixture. Finally, 32.7 g of a yellow pigment are obtained.

Example 4

Example 1 is followed with the following changes: 1 g of Disperbyk 185 and 1 g of Slovafol 915 are added to the pigment-forming reaction mixture. This gives 31.8 g of a yellow pigment suitable for printing inks.

Example 5

Example 1 is followed with the following changes: a mixture of 210 ml of 30 water and 40 ml of formic acid is used to dilute the suspension, and the reaction mixture is stirred at room temperature for 1 hour and further refluxed for 5 hours. 33.2 g of a yellow pigment are obtained.

Example 6

Example 1 was followed with the following changes: a mixture of 125 ml of water and 125 ml of acetic acid was used to dilute the suspension. 35.5 g of a yellow pigment having a high brilliance and a greenish shade are obtained.

Example 7

Example 1 is followed with the following changes: 14.3 g of Ν, Ν-dimethylbarbituric acid is used instead of barbituric acid in the preparation of the monocondensate and 16.2 g of Ν, dimethyl-dimethylbarbituric acid for pigment condensation. 35.2 g of a yellow pigment are obtained.

Claims (1)

PATENT CLAIMS Process for the preparation of isoindoline pigments of the general formula V Wherein R is hydrogen, methyl, ethyl or phenyl, wherein in a first step in a water-miscible, inert organic solvent, phthalodinitrile is reacted with the sodium or potassium salt of barbituric acid or its derivatives of formula VI (VD, where R has and Me is Na or K, in a molar ratio of 1: 1 at pH 8 to 14 and 0 to 80 ° C, and the monocondensate of formula VII formed Wherein R and Me are as defined above, react in a second step with a 1.01 to 1.5 molar excess of barbituric acid or said derivatives thereof at a pH of 0.1 to 6 in the presence of 5 water in a ratio of 25 to 500% by weight, based on the organic solvent.