Accelerator MBT is the product with the largest output among rubber vulcanization accelerators. The advantages of acid-base method M are good quality, high purity, and good application effect of rubber products. However, the acid-alkali production process commonly used in China has problems such as high raw material consumption in the refining process and serious environmental pollution. The generated wastewater has the characteristics of high salinity, high concentration of pollutants and is difficult to degrade, so the wastewater treatment is difficult.
At the same time, the acid-base production process also has the problem of waste gas and waste residue discharge. The cleaner production technology of accelerators has also become a hot spot and difficulty in technology development in the rubber additives industry in recent years.
Cleaner Production Process Analysis of Rubber Accelerator
The clean production of rubber accelerators has also become a hot spot and difficulty in technology development in the rubber additives industry in recent years.
The cleaning process adopts the solvent method, and the original alkali dissolution and acid precipitation processes are replaced by organic solvents. It used to be more than 20 tons of dilute lye, dilute sulfuric acid and process water to produce 1 ton, but now it does not use solvents with water. Naturally, no waste water will be generated without water, and the goal of source treatment will be achieved.
Based on the domestic annual output of 200,000 tons of accelerators, after the promotion of the whole industry, the annual waste water production can be reduced by 4 million tons, the discharge of inorganic salt (sodium sulfate) by more than 100,000 tons, and the COD emission by 800 tons. Comprehensive utilization of waste gas is realized.
Cleaner Production Safety Requirements for Rubber Accelerators
Environmental protection, safe and efficient selection of new organic solvents is the key to solvent purification. The existing extraction solvent methods mainly include solvent crystallization, distillation-extraction, solid-liquid extraction, liquid-liquid extraction, etc., but the technology is not perfect enough. .
At present, organic solvents can be selected from toluene, carbon disulfide, aniline, benzene and the like.
(1) Using carbon disulfide as a solvent, cost control and safety control are prominent issues. Although the quality is stable and the product can meet international requirements, the safety needs to be improved because carbon disulfide is flammable and explosive.
(2) When aniline is used as a solvent, aniline is slightly soluble in water, which will increase the amount of aniline in the solution, which is not conducive to production.
(3) Benzene and toluene are used as solvents, which have little solubility in resin and affect the purity of the product M. Solvent recovery must also be considered, and benzene and toluene are flammable and explosive, have low safety factors, and are volatile and cause solvent loss in the air. , leading to an increase in production costs, but also harmful to the atmospheric environment.
Process steps of fully enclosed filter washing and drying machine for refining and purifying rubber accelerator by solvent method
(1) Extraction and refining
First, add a composite solvent into the reactor (the composite solvent is a mixture of carbon disulfide, chloroform and tetrachloroethylene), start stirring and reflux, and adjust the stirring speed; then slowly add the crude product of 2-mercaptobenzothiazole synthesized by the conventional high-pressure method into the reactor In the process, the temperature was raised to 60°C for extraction and purification;
(2) Washing and purification
After the heat preservation is over, lower the temperature to 25°C, and then perform solid-liquid separation (the solid product and the mixed solvent mother liquor are obtained after the solid-liquid separation, and the obtained mixed solvent mother liquor is distilled to obtain the mixed solvent for reuse), and the separated solid is separated using a composite solvent. Washing, wet product is obtained after washing;
(3) Low temperature drying
The obtained wet product was dried (the drying temperature was 110° C., and the drying time was 5 h), and the refined vulcanization accelerator 2-mercaptobenzothiazole was obtained after drying.
(4) The appearance of the refined accelerator obtained is light yellow powder, with an initial melting point of 175.0°C. HPLC analysis shows that the product has a purity of 98.66% and a yield of 93.72%.
(1) One machine is multi-purpose, and can complete various operations such as reaction, extraction, filtration, repeated filtration, washing, and drying in one machine, and the finished product can be obtained directly.
(2) The operating flexibility is large, and the operating cycle can be adjusted by adjusting the filter pressure difference, rotating speed, screw extrusion lead, etc., so as to adapt to changes in process conditions.
(3) The machine can form a very thin filter cake on the surface of the filter medium or filter under the condition of no filter cake. The filtration rate per unit filter area is very high, so the equipment is small and compact.
(4) Fully enclosed system with good operating environment, especially suitable for handling toxic, flammable and explosive dangerous products and delicious food, biological products and pharmaceuticals that are not allowed to be polluted.
(5) It can be concentrated and filtered. Especially when it is necessary to wash the material, the material can be concentrated first, washed in a suspended state, and finally press-filtered, which can reduce the handling of the material, reduce waste, and do not need to re-pulp during washing. The quality of the processed product very high.
(6) It can be used for the three operations of reaction, filtration, and drying, so that the functions of the three unit equipment can be completed on this one equipment, so that the equipment cost, floor area, labor intensity, energy consumption, etc. are greatly reduced.
(7) The power consumption of this machine is low, and the extruded filter cake generally has lower water content than the flat three-in-one machine, and the operation is also convenient.
As the country pays more and more attention to environmental protection issues, Wuxi ZhangHua and scientific research institutions have intensified their research on the solvent method. The newly developed fully enclosed filter washing and drying machine can meet the safety requirements of the solvent method rubber accelerator refining and purification process. Realize clean production and lay a solid foundation for the long-term development of the rubber additives industry!