CS221005B1 - Process for treating mother liquors from filtration of the reaction product to produce N-cyclohexylbenzothiazole-2-sulfenamide - Google Patents

Abstract

The mother solutions, obtained after separation of N-cyclohexylbenzthiazole-2-sulfenamide from the reaction mixture after the oxidative condensation of the cyclohexylamine salt of 2-mercaptobenzthiazole, prepared from the raw melt of 2-mercaptobenzthiazole and an excess of cyclohexylamine, with sodium hypochlorite solution, do not crystallize at elevated temperature; split into two layers. After their separation, cyclohexylamine is regenerated from each layer by special distillation. The team achieves a better use of cyclohexylamine and a substantial improvement in the quality of wastewater.

Description

It is an object of the present invention to provide a process for treating mother liquors from the filtration of the reaction product to produce N-cyclohexylbenzothiazole-2-sulfenamide.

N-cyclohexylbenztlazole-2-sulfenamide is used as a safe rubber vulcanization accelerator. A method for its preparation is described in Czechoslovak patent No. 114 693, in US patents 2 191 657, 2 268 467, 2 762 814, in German patents 855 564 and DAS 1 940 364.

A new technological process for the preparation of N-cyclohexylbenzothiazole-2-sulfenamide, by which a high purity product can be prepared, is the subject of AO 215 179.

The present invention relates to the oxidation reaction of the cyclohexylamine salt of 2-mercaptobenzothiazole, which is formed by direct reaction of the crude, unrefined high pressure reaction product of aniline, carbon disulfide and sulfur with sodium hypochlorite.

The processes for producing N-cyclohexylbenzothiazole-2-sulfenamide used today in the world do not regenerate cyclohexylamine. This is eliminated in the mother liquors. In addition to being highly loss-making, it increases the toxicity of wastewater.

In order to guarantee the technological process in economic and environmental terms, it is necessary after distillation of the mother product to undergo distillation in order to recover cyclohexylamine.

We have found that the recovery of cyclahexylamine from the mother liquors resulting from the production of N-cyclohexylbenzothiazole-2-sulfenamide according to AO 215 179 can be carried out in high yields on the principle of the present invention.

The principle of the invention is that the mother liquors are readily separated into two layers after filtration of the N-cyclohexylbenzothiazole-2-sulfenamide in its preparation according to AO 215 179. The top layer contains the major part of cyclohexylamine and its soluble organic substances, as well as water saturated with sodium chloride. The lower layer contains the bulk of water and sodium chloride, as well as a small proportion of cyclohexylamine and pitch-soluble organic substances soluble therein. It is advantageous to separate the mother liquors continuously and to process them separately on continuously operating distillation columns.

The process of mother liquor treatment according to the invention is illustrated but not limited by the following examples.

Example 1

790 g of mother liquors after filtration of N-cyclohexylbenzothiazole-2-sulfenamide containing 103 g of cyclohexylamine (CHA), 608 g of water, 61 g of sodium chloride, 13 g of pitch and 5 g of soluble unidentified substances are left in a separatory funnel for 15 min. at 60 ° C.

The separated bottom phase, containing 13 g of CHA, 498 g of water, 57 g of sodium chloride and 1.2 g of pitch, is distilled in a boiling flask equipped with a distillation head at atmospheric pressure. The temperature of the outgoing vapors is 93-94 ° C. Distil until the temperature reaches 105 ° C in a boiling flask. The distillate contains 12 g CHA and 15 g water. The residue contains 1 g CHA, 483 g water, 57 g sodium chloride and 1.2 g pitch.

The top layer containing 90 g of cyclohexylamine, 110 g of water, 5 g of sodium chloride and 11.8 g of pitch is distilled in the same apparatus as the lower layer at atmospheric pressure. The temperature of the outgoing vapors is 93-94 ° C. Distil when the temperature reached 115 ° C, in a boiling flask. The distillate contains 88.0 g CHA and 108 g water. The residue contains 0.5 g CHA, 2.0 g water, 5 g sodium chloride and 13.3 g pitch.

Example 2

4390 kg / h of mother liquors from N-cyclohexylbenzothiazole-2-sulfenamide filtration are continuously processed. The mother liquors are first preheated in a tube heat exchanger to a temperature of 60 C. The ^J continuously operating dejičke of phase separation.

502 kg / h of cyclohexylamine, 611 kg / h of water, 27.6 kg / h of sodium chloride and 72 kg / h of pitch flow through the top of the separator. This phase is injected into a continuously operating tray column. A 115 ° C temperature was maintained in the column digester and 94-95 ° C at the top of the column. 495 kg / h of cyclohexylamine, 605 kg / h of water are obtained at the top of the column. At the bottom of the column, 3.5 kg / h of CHA, 6 kg / h of water, 27.6 kg / h of sodium chloride and 75.5 kg / h of pitch are discharged.

Bottom aqueous phase of the separator with prietokoin

68.5 kg / h of cyclohexylamine, 2766 kg / h of water, 313 kg / h of sodium chloride are fed to a continuously operating tray column. A column temperature of 105 ° C at the top of the column is maintained at 93-94 ° C. 66.5 kg / h of cyclohexylamine and 81 kg / h of water were passed through the top of the column. 2.0 kg / h of cyclohexylamine, 2685 kg / h of water and 313 kg / h of sodium chloride were passed through the column.

Claims (1)

221005 SUBJECT A method for treating the mother liquors by filtration of the reaction product to produce N-cyclohexylbenzothiazole-2-sulfenamide by reacting 2-mercaptobenzothiazole, preferably in the form of a crude reaction product of the reaction of aniline, carbon disulfide, cyclohexylamine and an oxidizing agent. using an excess of cyclbhexylamine in an amount of 1.5 to 5.0 moles per mole of 2-mercaptobenzothiazole, characterized in that the liquid solutions are first continuously separated by a dense density at a temperature of 40 to 90 degrees Celsius, preferably at 60 ° C to an org. A NON-EXCESSIVE phase comprising cyclohexylamine, water, organic pitch from aniline, carbon disulphide and sulfur as well as dissolved sodium chloride and an aqueous phase containing sodium chloride and cyclohexylamine, followed by organic The aqueous phase is separated by distillation under atmospheric pressure of cyclohexylamine in the form of an aqueous solution, the remainder being Sodium chloride-containing organic pitch from the distillation of the organic phase is discarded and the effluent from the aqueous phase distillation is discharged as non-toxic waste after the water has been diluted.