According to the raw material route, there are mainly: 1) aniline method; 2) o-nitrochlorobenzene method; 3) N-methylaniline method; 4) N, N-dimethylformamide method ; 5) Dimethylamine method; 6) Halogenated aniline method; 7) Benzothiazole method; 8) O-chlorothiophenol method; 9) Nitrobenzene method, etc.
The specific synthesis process of Flexex's rubber vulcanization accelerator M is as follows: molten sulfur, aniline, CS2, and benzothiazole are added to a high-pressure reactor with stirring, and the reaction temperature is 250℃, the pressure is 5.87MPa, after the reaction is completed, release the pressure, the gas phase part is the generated H2S and unreacted CS2, and enters the sulfur recovery device and CS2 recovery device. Melted M enters the dissolving tank and is dissolved with NaOH solution, and the insoluble matter is removed by filtration. The filtrate is extracted with toluene to recover by-products benzothiazole and other tar. The toluene layer enters the solvent recovery process to recover benzene. The water layer is M sodium salt solution. According to the needs of downstream M derivative products, it can be used directly after concentration, or it can be acidified with acid and then dried to obtain dry crystal M.
The raw material consumption of Flexex's product M is the lowest in the world. The main reason is that the by-product benzothiazole is returned to the reaction kettle. As early as the 1950s and 1960s, Monsanto Company had done a lot of work in synthesizing M. First, the reaction by-product tar is refined, the benzothiazole by-product is extracted, and then the tar is returned to the reaction kettle. The second step is to use solvents to recover and refine crude M, which avoids unnecessary consumption of chemical refining processes and provides a simple and feasible process for industrial production.
Most of the by-product tar in the M production process is benzothiazole, followed by aniline, thiophenylenediurea, etc. According to literature reports, benzothiazole is the intermediate product of M. Benzothiazole and thiophenylenediurea can add S and CS2/S to form M.
Solvent extraction is used to refine the reaction mixture. The important purpose is to recover the by-product benzothiazole and to refine the M sodium salt at the same time. The solvents used can be: monochlorobenzene, o-dichlorobenzene, toluene, benzene, CS2 and polychlorethane.
During the extraction process, slowly add crude M to hot water, stir vigorously in the presence of surfactant, then add organic solvent, and continue stirring under emulsification until the temperature reaches 170°C.
Surfactants are: sodium dodecylbenzene sulfonate, sodium decylbenzene sulfonate, dibutyl ammonium dodecylbenzene sulfonate, alkali metal salts of sulfonated fatty alcohols, Alkali metal soaps, etc. When using ionic surfactants, after extraction, the first half of the solution must be filtered and acidified to pH 3-4.
The aniline method uses aniline, CS2, and S as the main raw materials. Since CS2 is a flammable and explosive dangerous chemical, it is very inconvenient to use. The company reported on the use of aniline, N, N'- The production process of synthetic accelerator M using dimethylformamide and S as raw materials.
The reaction temperature is 200-300℃, the optimal reaction temperature is 225-275℃, the pressure is 3.45-4.83MPa (gauge pressure), and the reaction time is about 12h, but the yield of this method is relatively low. Only 66%.
In addition, the company's patent also reports a product using aniline, dimethylamine and S as raw materials.
This method is equivalent to homemade carbon disulfide, which is difficult to transport and store, and reacts in it. It is carried out under 5.83MPa (gauge pressure), the time is about 3h, and the reaction yield is about 81% based on dimethylamine.
Hope to adopt