CS243572B1 - A process for preparing a pigment form of diftaloylcarbazole or dye - Google Patents

Abstract

A method for preparing a pigment form of a diphthaloylcarbazole dye of the formula by dissolving the dye in sulfuric acid with a concentration of 96 to 100% and reprecipitating it with water while cooling the resulting suspension. Precipitation with water is carried out either by pouring a solution of the dye in sulfuric acid into water while cooling it, or by adding water to the solution while cooling the resulting suspension.

Description

(54) A process for preparing a pigment form of diphthaloylcarbazole or dye

A process for preparing a pigment form of a diphthaloylcarbazole dye of the formula

by dissolving the dye in 96-100% sulfuric acid and back-precipitating with water while cooling the resulting suspension. Water precipitation is effected either by pouring the dye solution in sulfuric acid into the water while cooling, or by adding water to the solution again while cooling the resulting suspension.

The present invention relates to a process for the preparation of a pigment form of a diphthaloylcarbazole dye prepared by dehydrogenation cyclization of 1,5-di (1-anthraquinones of lamino anthraquinone by treatment with various Lewis acids, for example by treatment with TiCH in o-chlorobenzene.

into vigorously stirred and chilled water, the temperature of the resulting suspension not exceeding 20 ° C. Cooling may be performed externally or by adding ice to the stirred suspension. Likewise, the dye can be eliminated from the same solution in sulfuric acid by slowly adding water to the stirred solution in an amount necessary to reduce the sulfuric acid concentration to 82-85%. It is not necessary to cool the reaction mixture so intensively and its temperature can reach up to 80 ° C without negative consequences. The resulting acid suspensions should then be filtered and the pigment pastes washed with cold water, optionally with dilute sulfuric acid, until the acid reaction is lost. The good coloring properties of the obtained pigment can be further improved by known final treatments, e.g. grinding its aqueous dispersion or powder after drying.

The pigment prepared by the processes of the present invention differs from the original dye by the crystalline structure. In diffractographic analysis, the original dye exhibits the following interplanar distances and relative intensities:

The crude dye obtained by said cyclization - commonly referred to in the literature as carbazolization - is first purified by oxidation with sodium hypochlorite and then finalized by grinding with suitable dispersants to commercial form, marketed as an excellent vat dye (CI Vat Orange 11, constitution no. 70 805) for dyeing of cellulose fibers. Although several other vat dyes are also converted to the form of organic pigments, there is no known process for this dye that would allow such treatment industrially. This is probably due to the fact that the untreated dye, when applied as an organic pigment (lacquers, plastics), produces opaque brown shades with a very low coloristic spreading rate. Unsatisfactory application properties cannot be improved by some other cleaning operations, eg by intensive oxidation with a solution of sodium hypochlorite or sodium chlorate, recrystallization from organic solvents (o-dichlorobenzene, dimethylformamide) or precipitation of a dye from its solution in sulfuric acid by pouring into water without cooling the resulting suspension.

Research has now found that by dissolving the dye in sulfuric acid and precipitating it back with water while cooling the resulting suspension, an organic pigment with significantly better coloristic properties can be obtained under the conditions defined below than the original dye.

To dissolve the dye in sulfuric acid, it must be used in a high concentration, preferably 96 to 100%. The dye must be precipitated from the solution by pouring it

Dkx Irel

7.72 84 6.73 21 3.54 82 3.26 100 ALIGN! while its new crystal modification has these analogous values: dkx Irel 9.38 46 7.23 67 3.66 58 3.28 100 ALIGN!

The organic pigment obtained by the process according to the invention, when applied in lacquers and plastics, has up to twice the coloristic spreading rate of the original and, more importantly, a more yellowish-brown shade.

The examples below illustrate an embodiment of the invention. In the examples, the parts given are by weight.

Example 1

100 parts of dry dye prepared by carbazolizing 1,5-di- (1-anthraquinonylamino-ianthraquinone) was slowly and under stirring introduced into 2,600 parts of 100% sulfuric acid and after complete dissolution (at a temperature of up to 20 ° C) the dye was precipitated again by pouring this solution into vigorously 8,000 parts of ice and water were stirred so that the temperature of the resulting slurry did not rise above 20 DEG C. The slurry was filtered and the pigment paste washed with cold water until the acid reaction was lost and finalized using conventional 10 parts abietic acid. 104 parts of an orange powder, coloring varnishes and yellow-brown plastic with good color fastness were obtained.

Example 2

100 parts of the same dry dye were dissolved in 3600 parts of sulfuric acid by the procedure as in the example, and 600 parts of water were slowly added with stirring so that the temperature of the reaction mixture rose gradually up to 80 ° C. The precipitated crystals were aspirated, washed first with 1000 parts of 70% sulfuric acid and then with cold water until acidity was lost. After drying and grinding, 79 parts of an orange powder of the same coloristic properties as the pigment prepared according to Example 1 were obtained.

Claims (3)

SUBJECT A process for preparing a pigment form of a diphthaloylcarbazole dye of the formula INVENTION by precipitating the dye from a solution in sulfuric acid, characterized in that the dye is dissolved in 96-100% sulfuric acid and re-precipitated with water while cooling the resulting suspension. 2. A process according to claim 1, wherein the solution of the dye in sulfuric acid is poured into water while cooling the resulting suspension, the temperature of which is at most 20 [deg.] C. 3. The process of claim 1 wherein water is added to the solution of the dye in sulfuric acid while cooling, in an amount necessary to dilute the acid content of the mixture to 82-85% by weight, the temperature of the resulting suspension being at most 80 ° C.