RU2203276C2 - Method of synthesis of n,n'-dicyclohexyl-2-benz- thiazolsulfenamide - Google Patents

Abstract

FIELD: organic synthesis, rubber industry. SUBSTANCE: invention relates to industrial method of synthesis of N,N'-dicyclohexyl-2-benzthiazolsulfenamide used as accelerating agent of sulfuric vulcanization of rubber mixtures. Method is performed by interaction of 2-mercaptobenzthiazole alkaline or ammonium salt with N,N'-dicyclohexyl chloramines in the mole ratio 2-mercaptobenzthiazole : chloramines = 2: 1 at temperature 20-30 C, pH = 11.5-12.5 in medium of water-soluble solvent. Aqueous solution of C₁-C₃-alcohol is used as a solvent. Process is completed at achievement of value Redox-potential = = (-100)-(-150) mv. EFFECT: increased yield and enhanced quality of product. 3 cl, 4 ex

Description

 The invention relates to the technology of organic synthesis, namely the industrial method for producing N, N'-dicyclohexyl-2-benzthiazole sulfenamide, used as an accelerator of sulfuric vulcanization of rubber compounds.

 One of the methods for producing sulfenamide-type vulcanization accelerators is the interaction of 2-mercaptobenzthiazole or its disulfide derivative with the corresponding N-chloramines.

 A known method of producing benzthiazole sulfenamides, which consists in the fact that dibenzothiazolyl disulfide is reacted with the corresponding chloramine and amine in an organic solvent in the presence of water [US patent 3022300, cl. 260-247.1, published. 1962].

 The disadvantage of this method is the use of pure amine, which complicates the process technology.

Closest to the claimed invention is a method for producing sulfenamide, which includes the interaction of the corresponding chloramine and 2-mercaptobenzothiazole in an organic solvent not miscible with water [US patent 3658808, cl. 260-247.1, publ. 1972]. The process according to this method is carried out in the presence of the same amine used as an acceptor of hydrogen chloride at a temperature of 20-60 ^o C.

 The yield of the target product 95%. Purity 96%.

 The disadvantage of this method is the insufficiently high yield of the target product, the need to dilute the reaction mass with water during the operation to isolate the target product, which leads to the formation of an additional amount of wastewater, complicating the process associated with the method for isolating the target product and recovering the solvent described in the invention.

 The problem to which the present invention is directed, is the creation of a technological process for the production of N, N'-dicyclohexyl-2-benzthiazole sulfenamide (Sulfenamide DC), repeatedly reproduced on an industrial scale, providing a high and stable yield of the target product with high purity with an optimal combination of concentrations used ingredients.

 The problem is solved by a new method for producing sulfenamide DC.

The method is carried out by reacting an alkaline, for example, sodium, potassium or ammonium salt of 2-mercaptobenzthiazole with N, N'-dicyclohexylchloramine in an aqueous alcohol medium with a molar ratio of 2-mercaptobenzthiazole: chloramine equal to 1.1-1.3: 1, temperature 20 -30 ^o C and pH 11.5 ÷ 12.5. The process is completed when the value of the Redox potential is reached within: 100 ÷ minus 150 mV. To measure the Redox potential, a millivoltmeter, platinum and silver chloride electrodes are used.

 The target product is isolated from the reaction mass by filtration of the suspension, washed with water and dried. The filtrate is separated into layers and the organic layer without prior processing is sent for recycling to the stage of synthesis of sulfenamide.

 N, N'-dicyclohexylchloramine is obtained as a result of the interaction of industrially produced technical N, N'-dicyclohexylamine with an aqueous solution of sodium hypochlorite and is used in the process after separation of the aqueous layer.

 The alkaline salt of 2-mercaptobenzthiazole is obtained by reacting 2-mercaptobenzthiazole (in the form of a "dry" product with a basic substance content of 97-98% or in the form of an "aqueous" with a basic substance content of 40-95%) with an alkali metal hydroxide (sodium, potassium alkali), taken in crystalline form or in the form of aqueous solutions or aqueous ammonia. The process of obtaining the salt of 2-mercaptobenzthiazole is carried out in an alcohol environment selected for the preparation of N, N'-dicyclo-2-benzthiazolsulfenamide.

 According to the claimed method, the yield of DC sulfenamide is 98.5-98.8%, based on 2-mercaptobenzthiazole, on N, N'-dicyclohexylamine - 97%. The content of the basic substance is not less than 97%, the content of the residue insoluble in ethanol is less than 0.2%, the mass fraction of ash is 0.1%.

 The industrial applicability of the present invention is illustrated by the following examples of specific performance.

 Example 1

A. Synthesis of N, N-Dicyclohexylchloramine (hereinafter - DCCA)
40 ml of isopropyl alcohol, 0.105 mol of dicyclohexylamine are added to a glass reactor equipped with a stirrer, thermometer, dropping funnel, electrodes for measuring the Redox potential, and a solution of sodium hypochlorite with an active chlorine content of n / m 170 g / l is added with stirring. The process is carried out at t = 30-35 ^o C to achieve the Redox potential of 200-250 mV. The reaction mass is kept under stirring for 0.5-1 h, then the organic layer containing 30-35% DCCA is separated and used in the synthesis of sulfenamide. The output of DLCA 97%.

 B. Preparation of the 2-mercaptobenzthiazole sodium salt solution.

 60 ml of isopropyl alcohol, 20 g of “dry” 2-mercaptobenzthiazole (0.12 mol) are charged into a glass reactor equipped with a stirrer, thermometer, and dropping funnel and 8.2 ml of 40% sodium hydroxide are added. The reaction mass is stirred until a homogeneous clear solution is used in the synthesis of sulfenamide.

 B. Synthesis of N, N'-Dicyclohexyl-2-benzthiazole sulfenamide.

In a glass reactor equipped with a stirrer, a thermometer, a dropping funnel, electrodes for measuring pH and Redox potential, 90 ml of isopropyl alcohol are charged, then 3 ml of water and previously prepared N, N'-dicyclohexylchloroamine in the amount of 0 are added to it with stirring. 1 mol A solution of the sodium salt of 2-mercaptobenzthiazole in isopropyl alcohol is metered into the reactor at a rate allowing the pH of the medium to be maintained between 11.5 and 12.5. The process is carried out at a temperature of 25 ± 5 ^o C until the Redox potential of the reaction mass is reached in the range: 100 ÷ minus 150 mV and until an excess of 2-mercaptobenzthiazole appears in the reaction mass, which is determined by the drop reaction with bismuth nitrate. The reaction mass is kept under stirring for 1.5-2 hours and at a temperature of 20-25 ^o C, precipitated crystals of DC sulfenamide are separated by filtration, the sulfenamide paste is washed on the filter with water, squeezed and dried.

 35.6 g of DC sulfenamide are obtained with a basic substance content of 97%. The yield of the target product is 98.5%, counting on 2-mercaptobenzthiazole, taking into account the return of the filtrate, and 97%, counting on loaded chloramine.

 The mother liquor obtained after separation of crystalline N, N'-dicyclohexyl-2-benzthiazole sulfenamide is subjected to sedimentation. Separate the layer containing sulfenamide, N, N'-dicyclohexylamine, 2-mercaptobenzothiazole dissolved in isopropyl alcohol, and direct it to the synthesis step of N, N'-dicyclohexyl-2-benzthiazole sulfenamide in the next step.

 Example 2

 Analogously to example 1, a solution of the sodium salt of 2-mercaptobenzthiazole and DCCA is prepared.

Then, in a glass reactor equipped with a stirring device, a thermometer, a dropping funnel, electrodes for measuring pH and Redox potential, successively load with stirring: 30 ml of isopropyl alcohol, 3 ml of water, 70 ml of the organic layer from the mother liquor of a suspension of sulfenamide obtained according to example 1, and previously prepared N, N'-dicyclohexylchloramine in an amount of 0.1 mol. A solution of the sodium salt of 2-mercaptobenzthiazole in isopropyl alcohol is metered into the reactor at a rate allowing the pH of the medium to be maintained between 11.5 and 12.5. The process is carried out at a temperature of 25 ± 5 ^o C until the Redox potential of the reaction mass is reached in the range: 100 ÷ minus 150 mV and until an excess of 2-mercaptobenzthiazole appears in the reaction mass, which is determined by the drop reaction with bismuth nitrate. The reaction mass is kept under stirring for 1.5-2 hours and at a temperature of 20-25 ^o C, precipitated crystals of DC sulfenamide are separated by filtration. The sulfenamide paste is washed on the filter with water, squeezed and dried.

 35.6 g of DC sulfenamide are obtained with a basic substance content of 97%. The yield of the target product is 98%, counting on loaded 2-mercaptobenzthiazole, and 97%, counting on loaded chloramine.

 The mother liquor obtained after separation of crystalline N, N'-dicyclohexyl-2-benzthiazolsulfenamide is subjected to sedimentation and the layers are separated. The organic layer containing sulfenamide, N, N'-dicyclohexylamine, 2-MBT dissolved in isopropyl alcohol, is sent to the synthesis step of N, N'-dicyclohexyl-2-benzthiazole sulfenamide in the next step.

 Example 3

 The synthesis of N, N'-dicyclohexyl-2-benzthiazole sulfenamide is carried out under conditions similar to example 2 using the potassium salt of 2-mercaptobenzthiazole.

 35.4 g of DC sulfenamide are obtained with a basic substance content of 97%. The yield of the target product is 97.5%, counting on loaded 2-mercaptobenzthiazole, and 96.5% on loaded chloramine.

 Example 4

 The synthesis of N, N'-dicyclohexyl-2-benzthiazole sulfenamide is carried out under conditions analogous to example 2, using the ammonium salt of 2-mercaptobenzthiazole.

 35.4 g of DC sulfenamide are obtained with a basic substance content of 96.5%. The yield of the target product is 97%, counting on loaded 2-mercaptobenzthiazole, and 96% on loaded chloramine.

Claims (3)

1. The method of obtaining N, N'-dicyclohexyl-2-benzthiazole sulfenamide by reacting chloramine with an alkaline or ammonium salt of 2-mercaptobenzthiazole in an organic solvent, followed by isolation of the target product from the reaction mass by filtration, characterized in that the alkaline or ammonium salt of 2-mercaptobenzthiazole interacts with N, N'-dicyclohexylchloramine in a molar ratio of 1.2: 1, pH 11.5-12.5, temperature 20-30 ^o C in a miscible with water solvent, the process is completed at a Redox potential value within 100 ÷ minus 150 mV. 2. The method of claim 1, characterized in that as an organic solvent use an aqueous solution of alcohol (C ₁ -C ₃ ) containing water in an amount sufficient to dissolve the inorganic compounds formed during the synthesis of sulfenamide.  3. The method according to claims 1 and 2, characterized in that the filtrate obtained by isolating the target product from the reaction mass is used in subsequent syntheses of sulfenamide.