CS269641B1 - Process for preparing bis- (2,4-dimercapto-6-triazinyl) disulfide - Google Patents

Abstract

production of bis-(2,4-dimercapto-6-triazinyl)disulfide of formula I by reaction of cyanuric chloride in the presence of sodium carbonate or bicarbonate at a temperature of up to 10 C with an aqueous solution of sodium disulfide and the reaction is completed at a temperature of up to 100 °C after addition of sulfide or sodium hydrogen sulfide. This compound serves as an adhesive agent for the rubber - - textile system and as a crosslinking agent for crosslinking some polymers.

Description

The invention relates to a process for the preparation of bis- (2,4-dimercapto-6-triazinyl) disulfide of formula I

(I) sequentially reacting cyanuric chloride with sodium disulfide and sodium sulfide or bisulfide in the presence of sodium carbonate or bicarbonate.

Said substance serves as an adhesive for the rubber-textile system and also as a crosslinking agent for the sulfurization of some polymers, especially polyvinyl chloride. Such crosslinked polymers then show higher strength characteristics at low and high temperatures, lower migration of plasticizers and higher resistance to solvents and external physical influences.

The present process consists either in the reaction of potassium or ammonium rhodanide with chloride in an aqueous medium at -15 ° C to 20 ° C in the presence of carbonates or carbonic acid, or in the direct oxidation of trimercapto-s-triazine with hydrogen peroxide in hydrochloric acid at 65-75 ° C. The first of these methods is demanding in terms of equipment, from a technical point of view it takes too long, in addition to the main product, many structurally similar substances are synthesized and a large amount of polluted wastewater is eliminated during production. The second method, which is considerably simpler, provides a substance of very poor quality which contains more than half of the other oxidation products, in particular substances containing more than one disulfide bond in the molecule. The synthesis of this compound is also feasible with other oxidizing agents such as hypochlorite or iodine. Purification of the resulting mixtures of these substances is not easy, because these compounds are generally sparingly soluble, even in alkaline environments.

It has now been found that the process according to the invention makes it possible to obtain bis- (2,4-dimercapto-6-triazinyl) disulfide in high purity and in a yield of more than 90%. The process is that the cyanuric chloride is reacted at 0 to 10 ° C with an equivalent amount of a pre-prepared aqueous sodium disulfide solution in the presence of one to three equivalents of sodium carbonate or bicarbonate and the reaction is completed at up to 100 ° C after the addition of sulfide. or sodium hydrogen sulphide in an amount of two equivalents based on cyanuric chloride.

The practice of the reaction is to first prepare a solution of sodium disulfide in water either by directly dissolving it or by dissolving an equivalent amount of powdered sulfur in the sodium sulfide solution, and further dissolving the appropriate amount of sodium carbonate or bicarbonate in this solution. Cyanuric chloride is preferably added to the resulting mixture under cooling, preferably in the presence of a nonionic wetting agent. The procedure can also be carried out in the opposite way, ie a solution of sodium disulphide in water is slowly introduced into a suspension of cyanuric chloride in water with ice and a wetting agent. After the first condensation, when free sodium disulfide is no longer present in the solution, a calculated amount of sodium sulfide or hydrogen sulfide is added to the reaction mixture, either in the solid state or, preferably, in the form of an aqueous solution. The mixture is then slowly heated to 90-100 DEG C. and, after a negative test for the presence of free sulfide ions, the reaction mixture, preferably hydrochloric acid, is acidified to pH 4-6. solution by filtration and dried thoroughly after washing.

The following example describes how to carry out the reaction. The listed parts are by weight.

CS 269641 Bl

Example

350 parts of water are introduced into a vat equipped with a heating coil, in which 149 parts of technical grade 75% molten sodium sulfide are dissolved with stirring, 3 parts of a nonionic surfactant (e.g. Spolion 8) are added and 45 parts of powdered sulfur or sulfur flower are added. Now the temperature is slowly raised to 50 Ca and the mixture is stirred until the sulfur is completely dissolved and a dark orange solution is formed. Then the heating is turned off and the solution is made up to 500 volumes with water.

Meanwhile, in another vat provided with good extraction or better in a boiler, a mixture of 550 parts of cyanuric chloride, 300 parts of water and 700 parts of ice is prepared. Sodium disulfide solution prepared from the vat is admitted to this mixture with stirring, and at the same time sodium bicarbonate is added so that the reaction mixture still shows a weak alkaline reaction. A total of 240 parts of sodium bicarbonate is added to the mixture. Throughout the reaction, the temperature of the reaction mixture must be kept within a range of up to 10 ° C; it is possible to use defoamers (eg Lukosan). After all the disulfide solution has been added, the reaction mixture is stirred for 1 hour, then the condensation termination test is carried out and a sodium sulfide solution prepared by dissolving 596 parts of technical grade 75% molten sodium sulfide in 4,000 parts of water is admitted from the measuring cup. After slowly allowing this solution to rise within 3 hours, the temperature is allowed to rise spontaneously, after the addition is complete, the solution is heated to 90-95 ° C and maintained at this temperature for 1 hour. The sample taken must no longer show a positive reaction to free sulphide ions, then reduce the temperature by cooling to 60 ° C and slowly allow more hydrochloric acid until the external sample gives a positive reaction to Congo red. The solution is then allowed to cool without stirring and the precipitated bis- (2,4-dimercapto-6-triazinyl) disulfide is filtered off with suction. The cake is washed with water until acidity is lost and dried in a vortex dryer. The yield of the yellow product is 324 parts, which corresponds to 92% of theory.

Claims (1)

OBJECT OF THE INVENTION Process for the preparation of bis- (2,4-dimercapto-6-triazinyl) disulfide of formula I characterized in that the cyanuric chloride is reacted at 0 to 10 ° C with an equivalent amount of aqueous sodium disulfide solution in the presence of one to three equivalents of sodium carbonate or bicarbonate and the reaction is completed at up to 100 ° C after the addition of sodium sulfide or sodium hydrogen sulfide in an amount of two equivalents based on the cyanuric chloride used.