Study On The Technology Of One-step Synthesis Of Methyltin Mercaptoacetate

Methyl tin mercaptoacetate is the most prominent species of PVC heat stabilizers, which is widely used in the synthesis of PVC and related products. A lot of research has been done for its preparation and application. There are many disadvantages in conventional synthesis methods, such as complicated process, high cost and severe environmental pollution. To overcome the disadvantages above, methyl tin mercaptoacetate was synthesized in low-pressure by one-step method in this study, and the synthesis process parameters was optimized systematically as follows:Firstly, the traditional synthesis route was modified by replacing the purification of the intermediate with a intermediate absorption unit, which is easy-operated and low-cost.Secondly, analyzed and screened the traditional catalyst of the intermediates syntheticly, through experiments, trimethylamine hydrochloride was chosen as the catalyst. It is proved that this method has many advantages, such as mild reaction conditions, higher product yield and lower cost.Thirdly, the reaction conditions acquired for the synthesis of intermediates methyl tin chloride were optimized, and the results of the experiments showed that the yield of intermediates methyl tin chloride was above 83% in the condition of 200℃, 1～2MPa, reaction time 8 hours and the amount of catalyst being 3.5% of total mass of tin.Fourthly, crude methyl chloride was absorbed into the solvent-ethylhexyl mercaptoacetate with a self-made device after it was synthesized, and the conditions of preparing methyl tin issoctyl mercaptoacetate were optimized. When the mass ratio of methyl tin chloride to issoctyl thioglycolate =1:2, reaction temperature is 40℃, reaction time is 1 hour, the sodium carbonate adding rate is 30g/h in the first 30 minutes and 10g/h in the second 30 minutes,the experimental results showed that the yield of methyl tin mercaptide was 83.7%.Fifthly, HPLC and ICP Apparatus were used to analyze methyl tin mercaptoacetate, and the result showed that the technological index of the product reached the level of slandered pipe material.Finally, experiments were taken for the performance evaluation of methyl tin mercaptoacetate and the results showed that: the performance of methyl tin mercaptoacetate was as good as the products in the market, and could meet industrial application requirements.