Background and overview[1]
With the development of the rubber industry, the research and production of vulcanization accelerators have attracted more and more attention. Vulcanization accelerator plays a very important role in the rubber vulcanization process. It can greatly accelerate the reaction between rubber and vulcanizing agent, improve productivity, and also improve the physical and mechanical properties of vulcanized rubber. The accelerator czis a white or light gray powder with a molecular weight of 264.41, a relative density of 1.27 to 1.30, and a melting point of 90 to 108°C. Soluble in acetone, ethyl acetate, dichloromethane, carbon tetrachloride, benzene and other organic solvents, slightly soluble in gasoline and ethanol, insoluble in water. It can gradually decompose when exposed to heat for a long time. The storage stability period is half a year. It is a post-effect accelerator. There is no danger of scorch at operating temperature and has excellent scorch resistance. The promotion effect is very strong at the vulcanization temperature and the vulcanization time is short. It is especially suitable for natural rubber and synthetic rubber containing highly alkaline oil furnace reinforced carbon black. The rubber needs to be supplemented with zinc oxide and stearic acid. Used together with other accelerators, it can improve the tensile strength and tear strength of synthetic rubber and vulcanized rubber, with slight discoloration and no blooming. The vulcanized rubber has excellent aging resistance. The general dosage is 0.5 to 2 parts. Mainly used in the manufacture of tires, tapes, hoses, rubber shoes, cables and general industrial products. The main foreign manufacturers include Uniroyal, Vanderbilt, DuPont, Akron, Pennwalt, Monsanto, American and other companies in the United States, ICI Company in the United Kingdom, Bayer Company in Germany, ACNA Montecatini and Naugatuck S.P.A. in Italy, Ouchi Shinsei, Sumitomo and Three new companies.
Purpose[2]
Rubber vulcanization accelerator CZ, whose scientific name is N-cyclohexyl-2-benzothiazole sulfenamide, is a highly active post-effect semi-super speed accelerator with excellent scorch resistance, safe processing and short vulcanization time. . Adding alkaline accelerators, such as thiuram and dithiocarbamates, can enhance its activity. It is suitable for all kinds of rubber, with slight discoloration and no blooming. Vulcanized rubber products are resistant to aging, have strong tensile strength and elongation, and are suitable for manufacturing industrial rubber products such as tires, rubber shoes, and cables. It is suitable for rubber materials using furnace black, such as natural rubber, butyl rubber, isoprene rubber, styrene-butadiene rubber, nitrile rubber, EPDM rubber, etc. It is characterized by excellent scorch resistance and short vulcanization time. , no blooming, aging resistance, products resistant to heat, cracking and wear. It can be used as a vulcanization accelerator alone or in combination with other accelerators such as D, DT, TT, TS, etc. Used to prepare tires, tapes, cables, hoses and other general industrial supplies.
Preparation[3-5]
(1) Hydrogen peroxide oxidation method
The hydrogen peroxide oxidation method was successfully developed by the Czech company Dimitrova in 1948. The synthesis method first puts a certain amount of recycled cyclohexylamine into the reactor, and adds 2-mercaptobenzothiazole (accelerator M) under stirring. After stirring evenly, add fresh cyclohexylamine and continue stirring until M and cyclohexylamine are fully miscible into a slurry. Then add hydrogen peroxide dropwise within a certain period of time at a rate that ensures the reaction temperature is below 30°C. Stop adding hydrogen peroxide after the reaction reaches the end point, allow the reaction solution to cool down slightly and then put it into a suction filtration tank. After vacuum filtration, the filtrate is distilled and recycled. Hexylamine, the filter cake is washed with water several times and then dehydrated and dried to obtain the product. The hydrogen peroxide oxidation method produces no salt and is basically harmless to the environment. However, a large amount of wastewater is produced during the hydrogen peroxide oxidation process and the yield of the resulting product is low.
(2) Sodium hypochlorite oxidation method
The sodium hypochlorite oxidation method was successfully developed by Monsanto Company in the United States in 1948. The synthesis method first puts sodium hydroxide aqueous solution into the sodium hypochlorite reactor, and then introduces chlorine gas at a temperature below 20°C for reaction to prepare sodium hypochlorite. Add a certain amount of recycled cyclohexylamine to the oxidation kettle, add the accelerator M under stirring, stir evenly, add fresh cyclohexylamine, continue stirring to make M and amine fully miscible into a slurry, and then stir at a temperature lower than 30°C. Under the conditions, sodium hypochlorite is added dropwise to carry out the reaction. When the end point is reached, the addition of sodium hypochlorite is stopped. The reaction liquid is filtered by suction, and the filtrate is sent for distillation to recover cyclohexylamine. The filter cake is washed, dehydrated and dried to obtain the product. The sodium hypochlorite oxidation method has a stable process, simple operation, low equipment requirements and high product yield. It is a commonly used method in China. If there is research and development of a vulcanization accelerator CZ production process, its characteristic is that the ring is added to the beating kettle. Hexylamine, then add 2 to 3 times its volume of water, stir for 1 to 3 minutes (stir evenly), add accelerator M (add 0.7 to 0.8 kg of accelerator M per liter of cyclohexylamine), and stir for 1 to 2 hours Finally, pour the slurry into the oxidation kettle, turn on the stirring of the oxidation kettle, turn on the condensed water in the jacket coil of the oxidation kettle, control the temperature to 25-38°C, and first add hydrogen peroxide with a concentration of 16-20wt% at a rate of 250-350L/h. (The added amount is 1.5 to 1.8 times the volume of cyclohexylamine). After the dropwise addition is completed, a sodium hypochlorite solution with a concentration of 13-16wt% is added dropwise at a rate of 250 to 350L/h (the added amount is generally 0.45 to 0.45 times the volume of hydrogen peroxide). 0.55 times) to the end point, and then wash, spin, granulate and dry to obtain the finished vulcanization accelerator CZ. The chemical reaction equation is as follows:
(3) Oxidant-free synthesis method
The oxidant-free synthesis method was developed by Bayer Company in Germany in 1984. The synthesis method first adds a sulfide to the preparation kettle of dibenzothiazole disulfide (accelerator DM).�� amount of water, add accelerator M and sodium nitrite under stirring, add sulfuric acid at a certain speed, introduce air at 60°C and react to prepare accelerator DM, which is washed and dehydrated with water for the next reaction. . Add a certain amount of cyclohexylamine and water to the accelerator CZ reactor, heat to 50°C with stirring, add the DM prepared above within a certain period of time, and add a certain amount of 50% NaOH aqueous solution at the same time, and control the pH value at 11 ~12, after the addition is completed, continue stirring for 2 hours, then precipitate, filter, wash and dry the product to obtain the product. However, more auxiliary raw materials are consumed during production, the process is more complicated, and NO is released during production, which pollutes the environment. At the same time, a large amount of Na2SO4 aqueous solution will be needed. deal with. Therefore, this process has not yet been adopted by domestic and foreign manufacturers.
(4) Oxygen oxidation method
The oxygen oxidation method was successfully developed by a Dutch company in 1987. The synthesis method is to add water to a reactor with a jacket, temperature and pressure detection device, and stirrer, and add accelerator M, catalyst and Ammonia water, then raise the temperature to 50°C, add oxygen to bring the pressure to 0.4MPa, add a certain amount of cyclohexylamine within 3 hours, and then react for another 2 hours. When the oxygen intake is very small, the reaction reaches the end point, stop stirring, and the white precipitate is filtered , wash with water, dehydrate and dry to obtain the product, the filtrate and washing liquid are sent to distillation to recover ammonia and excess cyclohexylamine. The key to the oxygen oxidation method is to select a suitable catalyst with excellent performance. This method is still in the research stagein China.
Main reference materials
[1] Fine Chemical Dictionary
[2] Practical Fine Chemical Dictionary
[3] Green process for synthesizing vulcanization accelerator CZ by catalytic oxidation method
[4] CN201210310832.4 A vulcanization accelerator CZ production process
[5] CN201310467586.8 Method for producing rubber vulcanization accelerator CZ using hydrogen peroxide as oxidant two-drop method
[6] Preparation method of CN201410437020.5 vulcanization accelerator CZ
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