Methylchlorosilanes, distillation

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. 

Distillation of unreacted methylchloride and rectification of methylchlorosilane mixture... 

Distillation is conducted at the excess pressure of 0.5-0.55 MPa. From pressure container 1 the mixture is constantly fed into heater 2, from where at 50-60 °C it is sent to the feeding plate of rectification tower 3. In the tower, methylchlorosilanes and methylchloride are separated. Methylchlo-rosilanes from tank 4 are collected into collector 10. The temperature in the tank is maintained within 145-155 °C with vapour (1 MPa) fed into the tank jacket. Methylchloride is condensed in refluxer 5, which is cooled with Freon (-50 °C) from there part of methylchloride is returned into tower 3, and the rest through cooler 6 is collected into receptacle 8. The uncondensed methylchloride from refluxer 5 and cooler 6 is sent into condenser 7, and from there is poured into receptacle 8 and collector 9. The... 

Methylchlorosilanes are difficult to separate due to the closeness of some of their boiling points. It is especially difficult to separate pure dimethyldichlorosilane (the boiling point is 70.2 °C) devoid of methyltrichlorosilane (the boiling point is 66.1 °C), because the difference of their boiling points is only 4.1 °C. It is known that the efficiency of separating reactive mixtures depends on the number of theoretical plates in the rectification towers moreover, in distillation there is a certain dependence between the number of theoretical plates and the difference in the boiling points of the components. For precise distillation and compete separation of methyltrichlorosilane from dimethyldichlorosilane, one needs a rectification tower with the efficiency of 60-80 theoretical plates. 

Moreover, apart from dimethyldichlorosilane, the second component of high-viscosity oligomethylsiloxanes can be tank residue, which remains after the distillation of methylchlorosilanes. 

Raw stock tank residue after distilling methylchlorosilanes (40-55% of chlorine, not more than 3% of dimethyldichlorosilane) trimethylchlorosilane (33-45% of chlorine) oil or coke toluene (not less than 98% of the 109.5-111 °C fraction). 

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. 

How far the vapor-treating technique will be extended to building materials, minerals for ore-flotation processes, and other large-scale uses remains to be seen. Since the technique requires only a small amount of material, and since mixed methylchlorosilanes may be used directly without distillation or hydrolysis, the process should be much less expensive than using a coating of silicone resin or oil on the same surface. Used without waste, the methylchlorosilanes may prove even less expensive than the traditional water-repellent agents such as waxes and lacquers. 

Derivation (1) Silicon is heated in methyl chloride to yield methylchlorosilanes these are separated and purified by distillation and the desired compound mixed with water. A polymeric silicone results. (2) Reaction of silicon tetrachloride and a Grignard reagent (RMgCl), with subsequent hydrolysis and polymerization. 

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. 

Replacement of silyl groups. Ethyl diloroformate added dropwise with stirring at 20° under dry N2 to 2-trimethyl-silylbenzothiazole, and heated 3 hrs. at 90° with distillation of the resulting tri-methylchlorosilane -> ethyl 2-benzo-thiazolecarboxylate. Y 90%. F. e. s. 

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