p-PHENYLENEDIAMINE SYNTHESIS METHOD Russian patent published in 2010 - IPC C07C211/51 C07C209/56 C07C231/02 

FIELD: chemistry.

SUBSTANCE: invention relates to an improved method for synthesis of p-phenylenediamine which can be used in making aramide fibres and as vulcanisation accelerator. The method involves Hofmann regrouping terephthalic acid diamides and is distinguished by that, the starting material used is wastes from production of terephthaloyl chloride, terephthalic acid or terephthaloyl chloride with ammonia gas in a toluene or chloroform medium at temperature 70-250°C while stirring for 1.5-4.0 hours at molar ratio of initial reagents equal to 1:2-4 with subsequent separation by filtering the formed diamide and its treatment at room temperature first with aqueous sodium hydroxide or potassium hydroxide solution with weight ratio diamide:hydroxide:water equal to 1:1:10-13, and then at temperature ranging from -5°C to +5°C with aqueous sodium hypochlorite or potassium hypochlorite solution with weight ratio of active chlorine of 3-22% with subsequent holding at temperature 8.0-12.5°C for 3 hours, at 60°C for 0.25 hours and at 80°C for 1 hour. The obtained reaction mixture is filtered. The filtrate is dehydrated. A concentrated p-phenylenediamine solution is extracted with an extracting agent at weight ratio of concentrated p-phenylenediamine solution to extracting agent equal to 5:1 and filtered. The extracting agent is distilled and technical p-phenylenediamine is separated by vacuum distillation at residual pressure of 5-15 mm Hg in a nitrogen current at temperature 140-250°C with subsequent crushing in a crystalliser.

EFFECT: method reduces cost of product due to use production wastes, and increased output of end product.

2 cl, 9 ex