CS257894B1 - Method of high-pure 4,4-diamino-1,1-di-antraquinonyle preparation in pigment form - Google Patents

Abstract

Process for the preparation of very pure 4,4'-diamino-1,1'-diantrachinonyl in pigment particularly suitable for coloring polypropylene fibers in the mass using isolating pigment sulphate from its suspension in dilute sulfuric acid and subsequent regeneration 4,4'-diamino-1,11-diantrachinonyl by hydrolytic decomposition of the sulphate so as to isolation of pigment sulfate by exclusion from its homogeneous solution in sulfuric acid 65 to 75% by cooling from 100 to 150 ° C to 50 ° C to ambient temperature and subsequent separation.

Description

The present invention relates to the preparation of very pure 4,4'-diamino-1,1'-diantraquinonyl in pigment form, particularly suitable for dyeing polypropylene fibers in the mass.

Only high-quality pigments can be used for pigmenting plastics and synthetic fibers in the mass, which can be exposed without damage to the high temperatures required to melt the dyed mass. Furthermore, these pigments must be easy to process, i.e. they must easily form perfect dispersions in the dyed material. For example, the filterability test is used to control the quality of pigments intended for dyeing polypropylene fibers in the mass by extruding the pigment concentrate melt through a fine mesh system and monitoring the rate of pressure increase over the mesh.

By performing the test under standard conditions, the value of filterability, which is a fictitious pressure that would be obtained by extruding a concentrate containing 1 kg of pigment, can be obtained from the measured values by numerical extrapolation. The rapid increase in pressure, i.e. higher filterability, indicates the presence of imperfectly dispersed pigment particles clogging the screen apertures. Pigments which have been found to be filterable above 1200 MPa.kg ^- 1 are generally considered unsuitable for the application.

Pigment red whose color substance is 4,4'-diamino-1,1'-diantraquinonyl (Color Index Pigment Red 177) is suitable for dyeing polypropylene fibers due to the high general stability and good coloring properties. The method of the preparation of this substance to the pigment form is the subject of MS. AO 174 383. It involves precipitation of a pigment from a dilute sulfuric acid solution resulting from the final stage of the synthesis, pouring into excess water and treatment with resin-type substances.

The process of this AO yields a pigment whose quality greatly depends on the quality of the precursor feedstock for the final stage of synthesis and the accuracy with which the prescribed pigment processing procedure was followed. There are also clearly minor shortcomings in both directions, which are difficult to prevent in practice. Thus, in a series of preparations, the filterability of the pigment from different batches varied between 500 and 200 MPa / kg. Attempts to improve the quality of the product indicate the seriousness of this problem, for example, in AO 217 252, special cleaning of the semi-finished product has been proposed but has not been applied in practice.

Significant improvements in the quality of pigments of this type can generally be achieved by processes involving dissolution in sulfuric acid at a suitable concentration, precipitation of the sulfuric acid salt by diluting the original solution with water, filtering out the precipitated salt and separately hydrolyzing it back to the pigment. In these processes, the character of the resulting salt particles and, to a large extent, the final pigment determines the course of the sulfuric acid concentration change.

A general procedure is disclosed in DOS 2,360,792. This process is not suitable for the treatment of 4,4'-diamino-1,1'-diantraquinonyl, since it produces a too fine, very difficult to filter form sulfate and its hydrolysis also produces a pigment unsuitable. form.

It has now been found that at elevated temperature, a homogeneous solution of pigment in dilute sulfuric acid can be prepared from which a well-crystalline pigment sulfate suspension is formed upon cooling. This salt form can easily be separated from the mother liquors containing dissolved impurities by filtration and hydrolyzed back to pigment by stirring in water. The hydrolysis product is then a pigment in the form of a different form resulting from the process of AO 174 383 and DOS 2 360 792.

This form exhibits suitable properties for dyeing polypropylene fibers in the mass without further substantial modification of the particle size and character.

A method for preparing highly pure 4,4-diamino-l, 1 ¹ -diantrachinonylu pigmentary form, especially useful for dyeing polypropylene fibers in the mass, using insulation sulphate pigment from a slurry thereof in dilute sulfuric acid and subsequent regeneration of 4,4'-diamino According to the invention, the homogeneous solution of pigment sulfate in 65 to 75% sulfuric acid is slowly cooled from 100 to 150 ° C.

Celsius to 50 ° C to ambient temperature to form an optimally crystalline form of pigment sulfate

The crystalline pigment sulfate is treated in a known manner, i.e., filtered, hydrolyzed by stirring the filter cake in water and the pigment is obtained by filtration, washing the filter cake with water and drying. For dyeing polypropylene fibers in the mass, the obtained form is suitable without subsequent intensive fine comminution, it is only necessary to homogenize the pigment and convert it into lumps of powder resulting from an unsuitable drying process.

The starting solution of the pigment in sulfuric acid either generated as a product in the final stage of the synthesis, the desulfonation ¹ 4,4-diamino-1,1'-diantrachínonyl-3,3'-disulfonic acid, or may be obtained by dissolving the pigment in sulfuric acid, in where it is desirable to improve its purity and physical form. Preferably, an acid at a concentration at which the pigment is dissolved at normal temperature is also used for dissolution or desulfonation (insoluble impurities can be removed from the solution thus prepared, such as sand, etc.) and at a concentration suitable for formation of crystalline pigment sulfate is adjusted by adding water. However, it is also possible to use the acid of the recommended concentration directly for desulfonation or dissolution.

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Well-developed 4,4'-diamino-1,1'-dianthraquinonyl sulfate crystals are formed by slow crystallization by cooling a solution of this compound in dilute sulfuric acid, with a suitable combination of determining factors such as acid to pigment ratio, temperature ratios and conoent race acid.

In desulfonation, the relative amount of acid is prescribed for this reaction. 9 parts of 100% sulfuric acid per part of pigment are generally used to dissolve the already synthesized pigment.

The final acid concentration depends on whether a pigment was used to prepare the solution or whether the reaction mixture was treated after desulfonation. In the first case the optimum final acid concentration is 70%, in the second 75 i. Sulfuric acid at 75% concentration is also suitable for direct aspiration for desulfonation. If a more concentrated acid than 73% is used to dissolve the already desulfonated pigment, too much pigment remains dissolved in the mother liquor and the particle size is greater than optimum. If more dilute, e.g.

65% acid, it is not possible to prepare a pigment sulfate solution even at the temperatures achievable.

Even in these cases, by stirring the suspension at elevated temperature, crystalline pigment sulfate can be prepared well, but the final product exhibits less reproducible filterability at the propylene poles. The more dilute the acid in the isolation, the less effective the purification is, since possible impurities may crystallize together with the pigment.

The temperature regime is determined by the requirement that the salt pigment crystallize from a homogeneous solution in dilute acid. At the above acid concentrations, heating to 120-140 ° C is required. Under these conditions and the time required to process the reaction mixture, no observable side reactions occur.

The final cooling temperature determines to some extent the product losses in the mother liquors and the purity of the resulting pigment. As a rule, it is expedient and economical to cool the slurry to a temperature close to ambient temperature, i.e. 20 to 40 ° C, and with higher cleaning efficiency requirements higher temperatures can be selected. Isolation of the crystalline sulfate by filtration of the resulting suspension proceeds very easily, the process is also feasible on an industrial scale.

The advantage of said process is that its product is a pigment characterized by very good filterability! in polypropylene and the results are reproducible even when the quality of the starting material varies. A further advantage is that the pigment thus obtained is suitable for dyeing polypropylene fibers without intensive fine grinding, changing the particle size of the pigment.

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In applications other than dyeing polypropylene fibers in the mass, the more difficult dispersibility of the crystallites resulting from the process of the invention may negatively affect the pigment yield and cause an undesirable shade shift to the blue area. In these cases, it is advisable to include the dispersion on the colloidal bead mill as a final pigment treatment step and, if necessary, to supplement the application of the resin type substances according to AO 174 383.

The process according to the invention can also be used only as a method for purifying the pigment. The filtered pigment sulfate is then redissolved in sulfuric acid of the appropriate concentration and further processed according to AO 174 383.

The examples below illustrate the preparation process of the invention.

Example 1

Technical 4,4'-diamino-1,1'-diantraquinonyl (25 parts) was dissolved with stirring in 98.7% sulfuric acid (228 parts), at 25 ° C, water (94 parts) was added dropwise to the temperature does not exceed 110 ° C. The resulting suspension was dissolved by heating to 140 ° C, allowing the solution to cool slowly. After cooling to 30 ° C, the product was filtered off and washed with 70% sulfuric acid. The filter cake was added to water (500 parts), stirred, the suspension was heated to boiling, held for 10 minutes, and the pigment was filtered off. The filter cake was washed with water until neutral and dried at 80 ° C. 22.7 parts of pigment were obtained which, after homogenization in a impact mill, showed a filterability in polypropylene of 600 MPa / kg.

Example2

To 75% sulfuric acid (240 parts) heated to 110 ° C was slowly added, with stirring, sodium 4,4 ^L -diamino-1,1 ^L -diantraquinonyl-3,3 ^L- disulfonic acid sodium (32.4 ^L ). . The temperature of the resulting suspension was raised to 140 ° C and held at this temperature for 3 hours. During this time the starting material was desulfonation ¹ to 4,4 diamino-1,1'-diantrachinonyl and the slurry was changed to a clear solution. The reaction mixture was cooled to 30 ° C over 6 hours, the crystallized pigment sulfate was filtered off and processed to a pigment as in Example 1. 19.6 g of a pigment were obtained which, after homogenization in a impact mill, showed a filterability of 630 MPa.kg ^-1 .

Claims (1)

SUBJECT OF THE INVENTION A method for preparing highly pure 4,4'-diamino-1,1'-diantraohinonylu pigmentary form, especially useful for dyeing polypropylene fibers in the mass, using insulation sulphate pigment from a slurry thereof in dilute sulfuric acid and subsequent regeneration of 4,4 diamino ¹ -1,1'-diantraohinonyl by hydrolytic decomposition of sulphate characterized in that the isolation of pigment sulphate is carried out by precipitation from its homogeneous solution in sulfuric acid at a concentration of 65 to 75% by cooling from 100 to 150 ° C to 50 ° C to ambient temperature and subsequent separation.