CS266632B1 - A method of processing an amorphous form of disazopigments - Google Patents

Abstract

A method of processing into a crystalline form the amorphous form of disazo pigments of general formula I, where A is phenylene, optionally further substituted with one or two chlorine atoms, methyl, methoxy or cyano group and B is phenyl substituted with one to three groups such as chlorine, methyl, methoxy, cyano, nitro, carbomethoxy or carboxamidic group, in which the amorphous form of the azo dye of general formula I is heated under a pressure of up to 600 kPa, at a temperature of 100 to 150 °C in an environment of aliphatic alcohols.

Description

The invention relates to a process for the treatment of an amorphous form of disazopigments, in which the disazopigments of the formula I are used

COCH, COCH,

I ³ I

B-N = N-CHCOHN-A-NHCOCH-N = N-B (I) convert from a crystallographically unstable amorphous form to a stable crystalline form. In general formula I, A is phenylene and B is phenyl, optionally further substituted by groups which do not have a solubilizing character.

Disazopigments of the formula I are prepared in amorphous crystalline form, usually by customary diazotization of the active ingredient of the formula II.

b-nh ₂ (II) wherein B is phenyl substituted with one to three groups selected from the group consisting of chloro, methyl-, methoxy-, cyano-, nitro-, carbmethoxy-, carbethoxy- or carboxamidic and coupling diazo compounds in a molar ratio of 2: 1 with passive components of the formula III CH ₃ COCH ₂ CONH-and-NHCOCH ₂ COCH ₃ (III) wherein a is phenylene, optionally further substituted by one or two chlorine atoms, methyl, cyano metoxynebo.

Of the compounds of formula II, these are in particular:

2,5-dichloroaniline

2,5-dicarbmethoxyaniline

2,5-dicarbethoxyaniline

2,4-dichloroaniline

2-methyl-5-chloroaniline.

2-methyl-3-chloroaniline

2,3-dimethylaniline

2-nitro-4-chloroaniline

2-chloro-4-carboxamidoaniline

2-cyano-4-nitroaniline

2-methyl-5-carbmethoxyaniline

3-chloro-4-methoxyaniline

2-methyl-4-chloroaniline

2-methoxy-4-chloroaniline

2-methoxy-5-methylaniline

2,5-dichloro-4-nitroaniline

2,6-dichloro-4-nitroaniline

2,4,5-trichloroaniline

4-carbmethoxyaniline

4-carbethoxyaniline

Of the compounds of formula III, these are in particular:

1,4-bisacetoacetylaminobenzene

1,4-bisacetoacetylamino-2-chlorobenzene

1,4-bisacetoacetylamino-2-methylbenzene

1,4-bisacetoacetylamino-2-methoxybenzene

1,4-bisacetoacetylamino-2-cyanobenzene

CS 266 632 Bl

1,4-bisacetoacetylamino-2,5-dichlorobenzene

1,4-bisacetoacetylamino-2,5-dimethylbenzene.

1,4-bisacetoacetylamino-2-chloro-5-methylbenzene

The coupling of the diazo substance with the passive component is usually carried out in an aqueous medium at a suitably selected pH of the reaction mixture, temperature, method of dosing both components, etc. The pigments obtained by this process are amorphous crystallographic. . The influence of the physical form of the pigments on their application properties is generally known, in this case the pigments of general formula I, the amorphous form has a lower yield, a more turbid shade and usually also a lower migration stability in softened PVC. A serious disadvantage limiting the use of the amorphous form of these pigments is that they undergo a thermodynamically more stable crystal modification by the action of a number of organic solvents. This recrystallization, which occurs in particular by the action of aromatic solvents only when applied in paint systems, for example in alkyd paints, results in a change in the hue and color strength of the paint as well as changes in the flow properties of the paint system. Recrystallization occurs either during the dyeing of the system or during its further storage, and pigments with such properties cannot be used in practice for these cases.

So far known procedures described eg in Czechoslovakia. pat. 177 066 therefore recommend treating pigments of this type in advance, by heating in organic solvents boiling above 100 ° C. Heating in xylene, chlorobenzene, nitrobenzene, pyridine, dimethylformamide, cyclohexanone and other solvents boiling above 100 ° C is recommended, with changes in the crystalline form of the pigments occurring by heating to 100-150 ° C. After recrystallization, the pigment is isolated from the suspension by filtration, if a water-immiscible solvent has been used, the filter cake is washed first with ethanol and then with water. Filtration, due to the small pigment particles, requires efficient filtration equipment and the solvent mixtures obtained need to be regenerated.

It has now been found that in a process for the treatment of an amorphous form of a disazopigment of general formula I.

C0CH ₇ COCH.

II d

BN = N-CHCOHN-A-NHCOCH-N = NB (I) wherein A is phenylene optionally further substituted by one or two chlorine atoms, methyl, methoxy or cyano and B is phenyl substituted by one to three groups such as chlorine, methyl-, methoxy, cyano, nitro, carbmethoxy, carbethoxy or carboxamidic group, the amorphous form of the azo dye of formula I is converted to the crystalline form by heating under elevated pressure up to 600 kPa, at a temperature of 100 to 150 ° C in an environment of aliphatic alcohols having carbon numbers. 1 to 3, optionally in an aqueous-alcoholic medium or even in water itself.

The effect of this treatment is further enhanced when working in the presence of hydrazine in an amount of 0.01 to 0.6 moles of hydrazine per mole of disazo dye. In this case, the recrystallization cleaves the monoazo dye, which is always present to a lesser extent in the diazo dye, into non-colored products, thus improving the stability of the resulting pigment in solvents and in migration. The reducing effect of hydrazine is preferably catalyzed by salts of manganese, zinc or tin.

The following examples document the process of the invention. Percentages are by weight.

Example ‘

The diazotized 2,5-dicarbmethoxyaniline is coupled in an aqueous medium with 1,4-bisacetoacetylaminobenzene in a molar ratio of 2: 1. The resulting disazo dye is filtered hot from the aqueous medium, the inorganic salts are washed out of the filter cake with water and the yellow pigment is obtained in amorphous form by drying. 72 g of this finely ground pigment are stirred in 900 ml of 96% ethanol and heated in an autoclave at 130 DEG C. for 8 hours at a pressure of 550 kPa with stirring. After cooling

CS 266 632 B1 at 70 DEG C., the crystalline pigment formed is filtered off, washed with hot water, dried and ground. The pigment obtained is in a stable crystal modification characterized by interplanar distances which are identical to the crystal modification prepared by heating the amorphous form in dimethylformamide, pyridine, or in other solvents.

The main crystallographic data are given in the following table:

Table d (A °) 16.02 8.82 7.95 5.31 5.02 4.61 4.08 3.32

I rel 13 74 25 22 12 26 17 100

The mean particle size is 0.23 .mu.m and is approximately the same as after heating the pigment in dimethylformamide at 130 DEG C. for 1 hour.

Example 2 g of a disazo dye prepared by coupling 2,5-dicarbethoxyaniline with 1,4-bisacetoacetylamino-2-chloro-5-methylbenzene is stirred in 900 ml of an ethanol-water mixture (1: 1 by volume). After adding 1 ml of a 45% strength aqueous hydrazine solution ₍ i.e., 0.015 mol and 0.1 g of MnSO 4 dissolved in 5 ml of water), the suspension is heated with stirring in an autoclave at 130 DEG C. for 6 hours at a pressure of 300 to 400 kPa. After cooling to 70 DEG C., the suspension is filtered off, washed with water and the aqueous paste is dried and ground to give 73 g of a yellow crystalline dye which, in oil oil, is equally abundant, slightly redder and slightly more turbid than the pigment obtained by crystallization from cyclohexanone. .

Example 3

380 g of an aqueous dye paste prepared by coupling diazotized 2,5-dicarbmethoxyaniline with 1,4-bisacetoacetylamino-2-chloro-5-methylbenzene containing 76.5 g of amorphous dye are stirred in 1000 ml of water and heated in an autoclave to 140 to 145 ° C for 10 h at a pressure of 360 to 410 kPa. After recrystallization, the pigment is isolated in the usual manner.

Example4

Λ.

390 g of an aqueous dye paste identical to Example 1 containing 72 g of dry matter are stirred in 580 ml of 96% ethanol, 4 ml of a 45% strength aqueous hydrazine solution, i.e. 0.06 mol and 0.2 g of MnSO4 are added, and the mixture is heated in an autoclave at 130-135 ° C for 6 h. After isolation, washing with water and drying, 70 g of a yellow crystalline pigment containing 0.1% of a monoazo dye are obtained, in contrast to the starting dye, which contained 0.8% of a monoazo dye. Compared to the pigment prepared by recrystallization, of the amorphous form of o-dichlorobenzene, the pigment according to the invention is 20% more abundant and slightly greener when assessed in the alkyd lacquer PL-65.

Example 5 g of a disazo dye prepared by coupling diazotized 2-methoxy-5-methylaniline with 1,4-bisacetoacetylamino-2-chloro-5-methylbenzene in a molar ratio of 2: 1 is heated in an autoclave for 8 h at 100-110 ° C in mixtures with isopropanol with the addition of 0.001 5 mol of hydrazine and 0.1 g of MnSO 4. A reddish-yellow pigment in a finely crystalline state is thus obtained.

Example 6 g of an amorphous pigment prepared by coupling diazotized 2-nitro-4-chloroaniline with 1,4-bisacetoacetylaminobenzene in an aqueous medium at 0-5 ° C and pH = 5 are stirred in 800 ml of 50% ethanol and heated in an autoclave for 5 hours. to a temperature of 120 ° C under pressure

CS 266 632 Bl

200 to 300 kPa. A crystalline tan pigment is formed which is isolated in the usual manner. .

Example?

300 g of an aqueous paste of disazo dye with a dry matter of 20, prepared by coupling diazotized 4-carbmethoxyaniline with 1,4-bisacetoacetylaminobenzene, are mixed in 900 ml of 60% ethanol. 2 ml of an aqueous solution of hydrazine with a concentration of 45% and 0.1 g of ZnSO ₄ are added to the suspensions. Heating in an autoclave at 120 DEG C. for 5 hours gives a pigment in crystalline form suitable for coloring paints.

Example 8 g of a disazo dye prepared by coupling 2,3-dimethylaniline with 1,4-bisacetoacetylaminobenzene is heated in isopropanol with the addition of 0.02 mol of hydrazine and a catalytic amount of MnSO ₄ under the conditions described in Example 5. 53 g of a yellow dye are obtained in crystalline form suitable for pigmentation of paints.

Claims (2)

OBJECT OF THE INVENTION A process for the treatment of an amorphous form of disazopigments of the general formula I coch ₃ COCH, I ^{2 3} BN = N-CHCOHN-A-NHCOCH-N = NB (I) wherein A is phenylene optionally further substituted by one or two chlorine atoms, methyl, methoxy or cyano and B is phenyl substituted by one to three chlorine, methyl -, methoxy-, cyano-, nitro-, carbmethoxy-, carbethoxy- or carboxamidic group in crystalline form, characterized in that the amorphous form of the azo dye of general formula I is heated under elevated pressure up to 600 kPa, at a temperature of 100 to 150 ° C in the environment aliphatic alcohols with a carbon number of 1 to 3, optionally in an aqueous-alcoholic medium or even in water itself. 2. The method according to item 1, characterized in that the heating is performed with the addition of 0.01 to 0.6 moles of hydrazine per mole of disazo dye, preferably catalyzed by Mn, Zn or Sn salts.