CS250994B1 - Process for the purification of 2-hydroxy-3- (4'-acetamino-N-phenyl) naphthamide - Google Patents

Abstract

The solution relates to a method for purifying 2-hydroxy-3-(4'-acetamido-N-phenyl)-naphthamide, prepared by reacting 2-hydroxy-3-naphthoyl chloride with 4-aminoacetanilide in a heterogeneous medium in the presence of surfactants, e.g. alkyl polyglycol ethers. The procedure according to the solution allows for reliable removal of reaction by-products by washing in an aqueous ammonia medium and optionally in a solution of ammonium salts, such as in chloride, sulfate or ammonium carbonate at pH 8 to 11 at a temperature of 60 to 120 °C, finally the purified product is filtered off and washed.

Description

The invention relates to a process for the purification of 2-hydroxy-3- (4'-acetamido-N-phenyl) -naphthamide prepared by the reaction of 2-hydroxy-3-naphthoyl chloride with 4-aminoacetanilide in a heterogeneous environment. In the presence of surfactants such as alkyl polyglycol ethers.

The crude product is often contaminated with by-products of synthesis and must be subjected to a refining process for dyeing purposes. Prior methods of purification of 2-hydroxy-3- (4-acetamido-N-phenyl) -naphthamide by washing with hydrochloric acid acidified water to pH 4 to 6.5, filtration and washing with water were poorly effective and did not remove accompanying impurities from the synthesis of the crude product , whose quality as a dyeing semi-finished product was not satisfactory.

The above disadvantages are eliminated by a process for the purification of 2-hydroxy-3- (4-acetamido-N-phenyl) -naphthamide in the presence of dispersants of the nonionic surfactant type, for example ethylene condensates such as alkyl polyglycol ethers / C 6 H 8 - (O-CH ₂ -CH ₂ ) _2Q - The object of the invention is that the purification is carried out in an aqueous ammonia medium having a concentration of ammonium hydroxide of 20 to 26% by weight, optionally replacing 5 to 50% by weight, preferably 20 to 35% by weight. ammonium hydroxide with an ammonium salt such as ammonium chloride, sulfate or carbonate, at the pH of the reaction mixture pH = 8 to 11 and a temperature of 60 to 120 ° C with constant stirring of the reaction mixture, then the purified product is filtered and washed with water.

The purification process according to the invention is illustrated by the following non-limiting and non-limiting examples.

Unless otherwise indicated, weight percentages are by weight.

He did

With stirring, 1200 l of water are introduced into the enamelled boiler and 120 kg of crude 2-hydroxy-3- (4'-acetamido-N-phenyl) -naphthamide in the form of a 40% aqueous paste are introduced, allowing 22 l of 25% ammonia water. weight percent, and added with 4 kg of alkyl polyglycol ether (-O-CH ₂ -CH ₂₎ 20 OH. After stirring briefly, the pH of the reaction mixture, which should be 8.5-10, is checked.

The boiler is sealed, the reaction mixture is heated to 85 ° C and kept at this temperature for 2 hours, then filtered on a filter press and washed with 400 L of 60 ° C warm water. 110 kg of 2-hydroxy-3- (4'-acetamido-N-phenyl) -naphthamide pure 100% are obtained.

Example 2

The procedure is the same as in the first exemplary embodiment except that instead of 22 L of 25% by weight ammonia water, 16 L of 25% by weight aqueous ammonia solution is used, together with the addition of 3 kg of ammonium chloride, 96 ° C and pH 8.5 to 9.0.

The product obtained does not contain foreign impurities which have not been removed by a known method of purification in a weakly acidic medium of hydrochloric acid at a pH of 4.5 to 6.0.

The advantage of the described purification method is that the synthesis by-products, which would otherwise impair the dye quality, can be largely removed in a simple way.

Claims (1)

Process for the purification of 2-hydroxy-3- (4'-acetamido-N-phenyl) -naphthamide prepared by the reaction of 2-hydroxy-3-naphthoyl chloride with 4-aminoacetanilide in heterogeneous medium in the presence of nonionic surfactant dispersants such as ethylene condensates such as alkyl polyglycol ether -CH ₂ -CH _{2 102} -OH) characterized in that the purification is carried out in an aqueous-ammoniacal medium having a concentration of ammonium hydroxide of 20 to 26% by weight, optionally replacing 5 to 50% by weight of ammonium hydroxide with an ammonium salt, ammonium sulfate or carbonate, at a pH of the reaction mixture of 8.0 to 11 and a temperature of 60 ° C to 120 ° C, while stirring the reaction mixture, then the purified product is filtered off and washed.