CS269944B1 - Process for preparing pure KOH adduct - Google Patents

Abstract

The sixth KOH adduct is prepared by recrystallization from its solution oxidized with hydrogen peroxide or chlorine. In the solution, the ratio of dye to KOH:water or a mixture of water and hydrogen peroxide is 2:4.5 to 10:14 to 46.

Description

The subject of the invention is a method for preparing a pure KOH addition compound of trans isomers of naphthoylenebenzimidazole, the hydrolysis of which in water containing a surfactant produces a pigment of very good yield, which dyes polypropylene silk in a bright orange color with an intensive yellow hue.

Condensation of 1,4,5,8-naphthalenetetracarboxylic acid with 1,2-diamminobenzene produces a mixed naphthalenebenzene-imidazole dye, which is optionally separated into trans and cis isomers, and the mixed dye and isomers are used as vat dyes or the isomers are finalised into pigments, which, due to their stability at high temperatures, have been used, especially recently, mainly in dyeing polypropylene silk. The different solubilities of their KOH addition compounds, prepared by heating the mixed dye in a medium containing water, ethanol and KOH, are usually used to separate the trans and cis isomers. The solid KOH addition compound of the trans isomers is separated from the soluble KOH addition compound of the cis isomers and processed into a vat dye or pigment.

When processing the KOH addition compound of trans isomers into a pigment, the KOH adduct is hydrolyzed either in boiling water or in water containing 0.05 to 1% pyridine, dimethylformamide or butylamine and the hydrolysis is then completed by acidifying the mixture with sulfuric acid or the aqueous-alcoholic alkaline paste of the KOH adduct of trans isomers is treated with a surfactant, for example the potassium salt of abletic acid and hydrolyzed while simultaneously acidifying the mixture to pH 5.5 to 6 with dilute sulfuric acid. The hue, purity and yield of the pigment are the better, the purer the hydrolyzed KOH adduct is.

It has now been found that the pure KOH adduct of the trans isomers of naphthoylenebenzimidazole can be prepared by oxidizing a suspension or solution of the KOH adduct of the trans isomers of naphthoylenebenzimidazole, wherein the ratio of dye: KOH: water or a mixture of 75 to 90% water and 10 to 25% 30% hydrogen peroxide in the solution is 2 to 4.5 to 10: 14 to 46, optionally also ethanol, with hydrogen peroxide or chlorine at a temperature of 20 to 90 °C and from the KOH adduct solution, optionally heated, filtered or filtered after clarification with activated carbon, the purified light yellowish or greenish-yellowish KOH adduct of the trans isomers is separated after cooling or after mixing the solution with ethanol containing KOH and cooling. This process for obtaining the pure KOH adduct of the trans isomers is the subject of the invention. The purified KOH adduct provides, by hydrolysis in water containing polyethylene oxide wax (solidification point 38-2 °C, density at 20 °C 1.15 to 1.17, trade name Apretár RV or Apretár p) or a chlorobenzene solution of polyethylene oxide wax at a temperature of 20 to 75 °C, the pigment form of trans isomers, characterized by yield and a bright yellow shade of orange color, even when dyeing polypropylene silk.

Example 1. in

The sharply suctioned filter cake of the KOH adduct of the trans isomers of naphthoylenebenzimidazole, containing 20 g of the dye dry matter, was suspended in 200 ml of 23.3% KOH diluted with 50 ml of 30% hydrogen peroxide, after three hours of stirring the suspension was heated to 50 °C, the solution was filtered and returned to the filtrate after filtering off the KOH adduct cake of the trans isomers, containing the KOH adduct solution of the cis naphthoylenebenzimidazole. After the addition of 57.8 g of solid KOH and cooling, the purified KOH adduct of the trans isomers crystallized, a light yellowish precipitate.

Example 2.

A sharply suctioned filter cake of the KOH adduct of the trans isomers of benzylimidazole, containing 20 g of the dye dry matter, was suspended in a mixture of 100 g of KOH, 330 ml of water and 100 ml of 30% hydrogen peroxide. After 30 minutes of stirring, the solution was filtered, mixed with 330 ml of 96% ethanol containing 115.6 g of solid KOH and cooled with ice water. The crystallized purified KOH adduct of the trans isomers was filtered off.

Example 3.

The sharply suctioned filter cake of the KOH adduct of the trans isomers, containing 2o g of the dye solids, was suspended in a mixture of loo g of KOH, 33o ml of water and loo ml of 3o % hydrogen peroxide. The suspension was filtered, loo ml of 96 % ethanol and 28o g of solid KOH were added, the reaction mixture was stirred for 1 hour, heated to 7o °C and stirred at this temperature for lo minutes. After cooling to 5 °C, cover —

CS 269944 Bl stated that the KOH adduct of the trans isomer appeared as greenish-yellow flakes and was filtered off. The filter cake weighed 50 g. The filtrate was separated into two layers, an upper reddish-brown layer containing the KOH solution of the cis isomer adduct and a clear layer of the KOH solution.

Example 4.

The preparation procedure was similar to Example 1 except that a suspension of the KOH adduct of the trans isomer in 2o to 25% KOH was oxidized with 5 g of chlorine, the temperature rising from 2o to 5o °C, then stirred for three hours, heated to To °C, filtered while hot and the filtrate treated as in Example 1 or 2.

Example 5.

A sharply suctioned filter cake of the KOH adduct of the trans isomer of naphthoylenebenzimidazole, containing 20 g of dry dye, was suspended in a mixture of 220 g of 40 to 44% KOH, 25 ml of 30 5= hydrogen peroxide and 100 ml of 96% ethanol and the mixture was heated to 70 °C. After cooling or filtering and cooling with ice water, the purified KOH adduct of the trans isomer crystallized as yellowish-greenish flakes.

Example 6.

The purified KOH adduct of the trans isomer was stirred in 4oo ml of 5 °C warm water, containing 1 g of Apretar RV or P or 1 g of Apretar RV or P dissolved in 4 ml of chlorobenzene. The suspension was stirred for 3 hours at normal temperature, or for another 3 hours at 0 °C, after cooling the dye was filtered off, washed with ethanol and water and dried at 8o to .9o °C. 18 g of pigment was obtained, characterized by yield and a bright, intense yellow hue.

Claims (1)

SUBJECT OF THE INVENTION A method for preparing a KOH addition compound of the trans isomer of naphthoylenebenzimidazole from an aqueous alcoholic alkaline medium, characterized in that the KOH addition compound is recrystallized after oxidation of its suspension or solution, containing 2 parts by weight of dye: 4.5 to 10 parts by weight of KOH: 14 to 46 parts by weight of water or a mixture of 75 to 90% water and 10 to 25% of 30% hydrogen peroxide, optionally also ethanol, with hydrogen peroxide or chlorine at a temperature of 20 to 90 °C, optionally after heating, filtering or filtering after clarification and activated carbon, optionally after mixing with ethanol containing KOH and cooling.