Methylchlorosilanes, distillation production

High viscosity (more than 1000 mm2/s) oligomethylsiloxanes can be prepared by the hydrolytic cocondensation of trimethylchlorosilane and tank residue after methylchlorosilane distillation with subsequent partial polycondensation of the obtained products. 

The production of sodium oligomethylsiliconate in this case comprises two main stages the hydrolytic cocondensation of the methylchlorosilane mixture the treatment of the hydrolysate with caustic soda. The reactive mixture, which consists of methyltrichlorosilane and tank residue from the distillation of methylchlorosilanes, is hydrolysed with water xCH3SiR3R3 nCln + yCH3SiCl3 + (x+y+l)H20 (x+y)HCi "... 

In the production of sodium oligomethylsiliconate agitator 3 (Fig. 54) is loaded with methyltrichlorosilane and tank residue from the distillation of methylchlorosilanes. The mixture is agitated at room temperature for 0.5 hours and poured into weight batch box 4, Then hydrolyser 5 is filled with a necessary amount of water and with 10% sulfuric acid from batch box 7. After that, backflow condenser 6 is filled with water, the agitator is switched on and the reactive mixture is gradually loaded from weight batch box 4 at such speed that the temperature in the apparatus does not exceed 45-50 °C. 

Eventually, the complete synthetic process will be executed in a new dedicated production unit as presented in Fig. 1. The necessary amounts of the different chloromethylsilanes and their corresponding precursors (methylchlorosilanes) are already available on an industrial scale within Wacker-Chemie. The alkoxylation process, a well-developed technology, will be run continuously as well whereas the carbamatosilane production will be a batch-type synthesis. The purified carbamatosilane will be fed into the tube reactor, in which the catalytic thermolysis will lead to the desired NCO-silanes. The latter will be isolated in high purity by distillation. 

The chemistry of silicones is summarized by following the steps necessary to produce a two-part, platinum-cured silicone containing vinyl-stopped polydimethylsiloxane, Si-H-on-chain siloxane, platinum catalyst and catalyst inhibitor. The process begins with silicon dioxide and follows the steps of conversion to sand to elemental silicon. Silicon is reacted with MeCl to make methylchlorosilanes in the methylchlorosilane reaction (MCS). The products from the MCS reaction are separated by distillation and then hydrolyzed and condensed to make the various siloxane polymers. Polymers with methyl, vinyl or Si-H functionality are made as required for the platinum addition-cured silicone product. 

Regarding the pyrolysis products of Me3SiCl, approximately 60 % of these products were separable by distillation at atmospheric pressure between 163-200 °C, and 40 % existed as oils and solids which were soluble in nonpolar solvents. Approximately 85% of the pyrolysis products of MeSiCl3 are colorless liquids, while the other 15 % are oils or meltable solids. Using gas chromatography, it was possible to detect all compounds with boiling points up to 250 °C formed by pyrolysis of the three methylchlorosilanes, as well as to establish the ratios of amounts of each compound present. 

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