CS249497B1 - Process for treating mother liquors from oxidative condensation of crude 2-mercaptobenzothiazole with sodium hypochlorite in excess cyclohexylamine - Google Patents

Abstract

The solution relates to a method of processing mother liquors from the oxidative condensation of crude 2-mercaptobenzothiazole with sodium hypochlorite in an excess of cyclohexylamine, after filtration of U-cyclohexylamine. The organic layer is separated at a temperature of 20 to 40 °C, an inorganic alkali solution is added to it, the aqueous solution of cyclohexylamine is distilled off and 2-mercaptobenzothiazole is separated from the distillation residue after acidification with mineral acid to pH 2. The solution can be used in the chemical industry.

Description

(54) Method for treating mother liquors from the oxidative condensation of crude 2-mercaptobenzothiazole with sodium hypochlorite in excess of cyclohexylamine

The present invention relates to a process for treating mother liquors from the oxidative condensation of crude 2-mercaptobenzothiazole with sodium hypochlorite in excess of cyclohexylamine, after filtration of U-cyclohexylamine. The organic layer was separated at 20-40 ° C, an inorganic alkali solution was added, the aqueous cyclohexylamine solution was distilled off, and 2-mercaptobenzothiazole was separated from the distillation residue after acidification with mineral acid to pH 2.

The solution can be used in the chemical industry.

I

The invention relates to a process for treating mother liquors from the oxidative condensation of crude 2-mercaptobenzothiazole with sodium hypochlorite in excess of cyclohexylamine.

Commonly known rubber accelerators of the sulfenamide type include N-cyclohexylbenzthiazole-2-sulfenamide used as a rubber vulcanization accelerator.

A continuous process for the production of U-cyclohexylbenzothiazole-2-sulfenamide in an excess of cyclohexylamine, by means of which a high purity product can be prepared, is the subject of U.S. Pat. AO number 215179.

It is based on oxidative condensation with simultaneous feed of crude 2-mercaptobenzothiazole as the unrefined product of the primary high pressure reaction of aniline, carbon disulphide and sulfur of an aqueous solution of sodium hypochlorite and cyclohexylamine.

The continuous regeneration of cyclohexylamine from mother liquors from the production of N-cyclohexylbenzothiazole-2-sulfenamide, consisting of two limited mixing liquids, is dealt with in U.S. Pat. AO 221005. Two layers are continuously separated at a temperature of 40 to 90 ° C.

The organic / topcoat layer containing excess cyclohexylamine, water, organic pitches from the high pressure reaction of aniline, carbon disulphide and sulfur as well as dissolved sodium chloride is subsequently separated by distillation at atmospheric pressure with cyclohexylamine as an aqueous solution used directly in the production of N-cyclohexylbenzothiazole-2- sulfenamide.

It has now been found to be advantageous to treat the mother liquors from the oxidative condensation of crude 2-mercaptobenzothiazole with sodium hypochlorite in excess of cyclohexylamine, after filtration of N-cyclohexylbenzothiazole-2-sulfenamide, after separation and distillation. an organic layer containing excess cyclohexylamine according to the method of the invention.

SUMMARY OF THE INVENTION The organic layer is separated at 20 to 40 ° C, 0.1 to 0.2 parts of a dilute inorganic alkali solution is added per 100 parts of the organic layer, the aqueous cyclohexylamine solution is distilled off from the distillation residue at atmospheric pressure. or from the separated aqueous layer after acidification with mineral acid to pH 2, free 2-mercaptobenzothiazole is separated.

By treating the mother liquors according to the invention, the efficiency of cyclohexylamine is increased by 5-9%.

recovery

It is well known that it is difficult to lead. a process of oxidizing 2-mercaptobenzothiazole with sodium hypochlorite in an excess of the amine component at a selectivity close to one or total conversion relative to 2-mercaptobenzothiazole.

The unreacted cyclohexylamine salt of 2-mercaptobenzothiazole dissolved in an excess of cyclohexylamine binds an equimolar amount of cyclohexylamine. The amine bound in this way is only partially regenerable, depending on the degree of alkalinity of the aqueous sodium hypochlorite solution used in the oxidation process.

A substantial increase in the efficiency of cyclohexylamine recovery with regard to cyclohexylamine bound in the cyclohexylamine salt of 2-mercaptobenzothiazole is due to the addition of an inorganic alkali.

In addition, by adding an inorganic alkali to the organic layer of the mother liquors from an aqueous solution of the alkali salt of unreacted 2-mercaptobenzothiazole separated from the distillate pitch waste, to obtain 2-mercaptobenzothiazole of 90% purity suitable for reuse for the production processing for other purposes.

The method of the invention also improves the technological feasibility of the degree of cyclohexylamine recovery from the organic layer of the mother liquors by reducing the risk of clogging of the bottoms, whose total weight decreases, from the bottom of the continuously operating distillation column.

These examples illustrate but do not limit the scope of the invention.

Example 1

From 470 g of the mother liquor obtained by filtration of N-cyclohexylbenzothiazole-2-sulfenamide from a continuous process, 101 g of the top organic layer containing 39.8% cyclohexylamine was distilled in a separatory funnel at a temperature of 22 ° C and distilled in a boiling flask with the addition of 100 g of water at atmospheric pressure. It was distilled only after reaching a leaving vapor temperature of 99 ° C.

120 g of distillate were obtained containing 30.15% cyclohexylamine. The recovery yield relative to the cyclohexylamine present in the distillation feed is 90%.

Example 2

From 950 g of the mother liquor obtained after filtration of the N-cyclohexylbenzothiazole-2-sulfenamide from the continuous process preparation, 200 g of the organic layer containing 39.8% cyclohexylamine were separated in a separatory funnel at 38 ° C.

After addition of 1 g of potassium hydroxide in 200 g of water, the organic layer was distilled on the apparatus and under the conditions of Example 1.

232 g of distillate were obtained containing 32.5% cyclohexylamine. The recovery yield relative to the cyclohexylamine present in the feed is 95%.

Example 3

Of the 460 g of mother liquor obtained after filtration of NTcyclohexylbenzothiazole-2-sulfenamide from continuous process preparation, 100 g of organic layer containing 39.8% cyclohexylamine were separated in a separatory funnel at 21 ° C.

After addition of 1.3 g of sodium hydroxide in 8 g of water, the organic layer was distilled on the apparatus and under the conditions of Example 1.

118 g of distillate were obtained containing 33.2% cyclohexylamine. The recovery yield for the cyclohexylamine present in the feed is 98.5%.

Further, 7.5 g of pitch impact and 55.3 g of an aqueous solution of 2-mercapto benzothiazole sodium salt were obtained, from which, after addition of the mineral acid to pH 2, 4.48 g of 2-mercaptobenzothiazole having a purity of 89.7% were obtained.

Claims (1)

The method according to the invention also improves the technological feasibility of the cyclohexylamine regeneration step from the organic layer of the mother liquors by reducing the risk of clogging of the residue of the distillation residue whose total weight decreases from the bottom of the continuously operating distillation column. These examples illustrate, but do not limit the invention. Example 1 From 470 g of the mother liquor obtained by filtration of N-cyclohexylbenzthiazole-2-sulfenamide under continuous operation, 101 g of the organic layer containing 39.8% of cyclohexylamine was distilled off in a separatory funnel at 22 ° C and distilled in a boil-beaker equipped with a distilled nozzle. adding 100 g of water at atmospheric pressure. 120 g of distillate containing 30.15% cyclohexylamine were obtained. The recovery yield of the cyclohexylamine contained in the feed to the distillation is 90%. EXAMPLE 2 Of the 950 g of mother liquor obtained after N-cyclohexylbenzthiazole-2-sulphenamide amide purification in a continuous process, 200 g of an organic layer containing 39.8% cyclohexylamine were separated in a separatory funnel at 38 ° C. After adding 1 g of potassium hydroxide in 200 g of water, the organic layer was distilled off under conditions as in Example 1. 232 g of distillate with a content of 32.5% cyclohexylamine were obtained. The recovery yield of the cyclohexylamine found in the feed is 95%. EXAMPLE 3 100 g of an organic layer containing 39.8% cyclohexylamine were separated from 460 g of the mother liquor obtained after filtration of NTcyclohexylbenzthiazole-2-sulfenamide by continuous operation in a separating funnel at 21 DEG. After the addition of 1.3 g of sodium hydroxide in 8 g of water, the organic layer was distilled on the apparatus and under the conditions of Example 1. 118 g of distillate with a content of 33.2% of cyclohexylamine were obtained. The recovery yield of the cyclohexylamine found in the feed is 98.5%. Further, 7.5 g of pitch impact and 55.8 g of an aqueous solution of 2-mercaptobenzothiazole sodium salt were obtained, from which 4.48 g of 2-mercapto-benzothiazole having a purity of 89.7% were obtained after addition of the mineral acid to pH 2. BACKGROUND A method for treating mother liquors from oxidative condensation of crude 2-mercaptobenzothiazole with sodium hypochlorite in excess cyclohexylamine, after filtration of N-cyclohexylbenzothiazole-2-sulfenamide, after separation and distillation! organic layer containing excess cyclohexylamine at atmospheric pressure, characterized in that the organic layer is separated at 20 to 40 ° C, 0.1 to 0.2 parts of dilute inorganic alkali solution is added per 100 parts of organic layer, at atmospheric pressure, distilling off the aqueous solution of cyclohexylamine and separating the free 2-mercaptobenzothiazole from the distillation residue or the separated aqueous layer after acidification with dopH 2.