Methylphenyldichlorosilane

West and co-workers [9,10] prepared polysilastyrene, a soluble and fusible polymer, by a Wurtz-coupling of dimethyldichlorosilane and methylphenyldichlorosilane (Eq. 4). Thermolysis of this polymer at 450°C results in a polycarbosilastyrene which can be cured by irradiation with UV-light in air at room temperature [11],... 

Methylphenyldichlorosilane is synthesised in two stages. First, chlorobenzene reacts with metallic magnesium in a xylene medium to form phenyl-magnesiumchoride ... 

Fig. 1. Production diagram of methylphenyldichlorosilane by organomagnesium-synthesis 1,2- dehydration boxes 3,4,7,11- batch boxes 5 - agitator 6, 9, 14 - coolers 8 - reactor of phenylmagnesiumchloride synthesis 10 - reactor of methylphenyldichlorosilane synthesis 12 — nutsch filter 13 — vacuum distill-ingtank 15-18- collectors 19- container.

The production process of methylphenyldichlorosilane by organomag-nesium synthesis (Fig. 1) comprises three main stages the production of phenylmagnesiumchloride the synthesis of methylphenyldichlorosilane the extraction of marketable methylphenyldichlorosilane. 

Apart from methylphenyldichlorosilane, the reaction also yields some methyldiphenyldichlorosilane, diphenyl, diphenylbenzene and other substances. The product is distilled in vacuum distilling tank 13, separating several distillates distillate I (up to 135 °C) contains a small quantity of the main product, unreacted methyltrichlorosilane and chlorobenzene, as well as xylene distillate II (up to 180 °C) always contains small quantities of the main product and xylene distillate III (180-300°C) generally contains the main product — methylphenyldichlorosilane distillate IV (more than 300°C) is usually separated under a residual pressure of 20 GPa and vapour temperature of 140 °C and is a mixture of methyldiphenylchloro-silane, diphenyl, diphenylbenzene and other impurities. To obtain pure methylphenyldichlorosilane, the products of distillation are subsequently rectified. 

Methylphenyldichlorosilane is a colourless liquid (the boiling point is 204°C) with a specific pungent odour characteristic of organochlorosilanes it fumes in air. It is also easily hydrolysed by water. 

Technical methylphenyldichlorosilane should meet the following requirements ... 

Methylphenyldichlorosilane is a source monomer in the synthesis of oligomethylphenylsiloxanes, various silicone elastomers and polymers used in the production of varnishes. 

Similarly to methylphenyldichlorosilane, one can obtain phenylethyldi-chlorosilane and other organochlorosilanes with different radicals at the silicon atom. 

When hydrogen chloride is fed into the reaction zone, the yield of methylphenyldichlorosilane increases. 

The synthesis of methylphenyldichlorosilane by dehydration is based on the interaction of methyldichlorosilane with benzene at heating under pressure ... 

The reaction is conducted in the presence of a catalyst, the solution of boric acid in methylphenyldichlorosilane with the mole ratio of parent reactants CH3SiHCl2 C6H6 of 1 3. The excess of benzene has a beneficial effect on the output of methylphenyldichlorosilane. It should be noted that in the synthesis conditions there is a disproportioning of methyldichlorosilane, which forms by-products, such as methyltrichlorosilane and di-methyldichlorosilane. These products can be separated in the process of the rectification of the condensate and added to the reactive mixture during the synthesis of methylphenyldichlorosilane to suppress the reaction of disproportioning. 

Raw stock methyldichlorosilane (not less than 98% of the main fraction, 61.3-62.5% of chlorine) benzene (d420 =0.876-0.879) technical boric acid. Methylphenyldichlorosilane production (Fig. 16) comprises three main stages the preparation of equipment and reactive mixture the synthesis of methylphenyldichlorosilane the rectification of methylphenyldichlorosilane. 

Fig. 16. Production diagram of methylphenyldichlorosilane 1-4 - batch boxes 5 -agitator 6 - batch box 7 - choke 8 - autoclave 9, 15, 23 -coolers 10- separator 11, 18, 19, 27 - collectors 12, 20 - rectification tower tanks 13, 21 - rectification towers 14, 22 - refluxers 16, 17, 24-26 - receptacles.

Methylphenyldichlorosilane is synthesised under pressure in an autoclave reactor. The apparatus has chokes, a thermocouple pocket and a siphon for checking the degree of its filling. Before the beginning of the synthesis the autoclave should be checked for hermiticity. For this purpose, the operating pressure of 10-12 MPa is created in the apparatus and held for 10 minutes. During this the pressure in the autoclave should remain constant. 

Head fraction I, which is a mixture of methyldichlorosilane, methyltri-chlorosilane, dimethyldichlorosilane and a small amount of benzene, is separated in the 36-78 °C range and collected in receptacle 16. Then this fraction can enter batch box 4. Fraction II (benzene) is distilled in the 78-82 °C range and collected in receptacle 11, and then poured into receptacle 18. It can be re-used in the synthesis (in this case benzene from collector 18 is sent into batch box 3). Tank residue, which after the distillation of the first two fractions is a concentrate with 50% of methylphenyldichlorosilane, is sent from tank 12 into collector 19 and from there into tank 20, heated with vapour (1.4 MPa). 

For 1 hour vacuum rectification tower 21 operates in the self-serving mode, and then starts separating benzene, which is collected in collector 24 (from there it can be sent to the synthesis again into batch box 3). After the distillation of benzene residual pressure of 107 GPa is created in the rectification system after the constant mode is established, the intermediate fraction is separated into receptacle 25. If the methylphenyldichlorosilane content in the intermediate fraction exceeds 5%, this fraction can be sent for repeated rectification in tank 20. After the intermediate fraction, the main fraction, methylphenyldichlorosilane, is separated into receptacle 26. The fraction with the density of 1.1750-1.1815 g/cm3 and chlorine content of 36.9-37.8% is separated. The separation is conducted as long as reflux is extracted. From receptacle 26, technical methylphenyldichlorosilane flows into collector 27. 

Thus, when methylphenyldichlorosilane is chlorinated in the presence of radical initiators (the dinitrile of 2,2 -azobis(isobutyric) acid, etc.), only the methal radical is chlorinated, while the phenyl radical is untouched. 

The technology of methylphenyldichlorosilane chlorination is similar to that of methylchlorosilanes. The main difference is that the radical chlorination of methylphenyldichlorosilane occurs at a sufficient speed at higher temperatures (100-110°C), than in the case of methylchlorosilanes (60-70°C). At lower temperature (50-70 °C) the chlorination of methylphenyldichlorosilane is slow, and at higher temperatures (140-150 °C) the bond Si—Caik is destroyed. This difference in the conditions for methylphenyldichlorosilane chlorination seems to be caused by spatial difficulties due to the presence of the phenyl radical. 

The technological diagram of the production of phenyl(chloromethyl)dichlorosilane is similar to the diagram given in Fig. 19. In this process, similar to methylchlorosilane chlorination, in order to maximise the yield of phenyl(chloromethyl)dichlorosilane, the original methylphenyldichlorosilane should have a low conversion degree otherwise, the process forms a great amount of products of a deeper chlorination. 

Raw stock methylphenyldichlorosilane (not less than 99% of the main fraction) methyl alcohol (not less than 0.5% of humidity) technical carbamide (urea), which is a colourless crystal substance with the melting point of 132-135 °C (not less than 0.2% of humidity) oil or coal toluene (the boiling point is 109.5-111 °C, d/° - 0.865 0.002) activated coal (not less than 0.02% of humidity). 

The viscosity of industrial oligomethylphenylsiloxanes, as well as that of oligomethylsiloxanes, varies from 4 to 1000 mm2/s. Similarly to oli-gomethylsiloxanes, oligomethylphenylsiloxanes are obtained by 1) the joint hydrolytic condensation of trimethylchlorosilane and methyl-phenyldichlorosilane with subsequent catalytic regrouping and partial polycondensation of the condensation products the separate hydrolytic condensation of trimethylchlorosilane and methylphenyldichlorosilane with subsequent catalytic regrouping of the condensation products. 

The synthesis of low-dispersion oligomethylphenylsiloxanes is based on the separate hydrolytic condensation of trimethylchlorosilane and methyl-phenyldichlorosilane. It comprises three stages the hydrolytic condensation of trimethylchlorosilane and subsequent distillation of pure hexame-thyldisiloxane the hydrolytic condensation of methylphenyldichlorosilane and subsequent depolymerisation of the formed methylphenylcyclosilox-anes the catalytic regrouping of the mixture of hexamethyldisiloxane and methylphenylcyclotrisiloxane. 

The hydrolytic condensation of methylphenyldichlorosilane in the excess of water forms both methylphenylcyclosiloxanes and a,co-dihy droxymethylphenylsiloxanes ... 

Hydrolyser 4 is filled with a calculated amount of water, the agitator is switched on, and methylphenyldichlorosilane is sent from batch box 2 under the water layer at such speed that the temperature in the apparatus does not exceed 80 °C. After the methylphenyldichlorosilane has been loaded, the mixture is agitated for 1 hour. To improve the splitting of the reactive mixture, the apparatus is filled with toluene from batch box 3. The mixture is agitated for 1 more hour after that the bottom layer (hydrochloric acid) is poured into collector 5, and the toluene solution of the products of hydrolytic condensation is flushed with water at high temperature (70-90 °C) until it gives a neutral reaction. 

The neutral solution is poured into collector 15, and from there into tank 16. The tank is also filled with a calculated amount of a 10% solution of lithium hydroxide. Vapour heating is started and toluene is distilled, first under atmospheric pressure, then in vacuum. The distillation is finished when the distillate no longer enters receptacle 18, which is achieved approximately at 180 °C and a residual pressure of 52-80 GPa. From the receptacle, toluene is sent into batch box 3 for repeated use. The products of the hydrolytic condensation of methylphenyldichlorosilane, methylphenyl-cyclosiloxanes, are sent from tank 16 into collector 19 and then into tank 20 to decompose. 

The formation of cyclic compounds increases with the size of the organic radicals bound with silicon. For example, in the process of hydrolytic condensation methylphenyldichlorosilane and diphenyldichlorosilane form mostly cyclic products. The conditions of the hydrolysis of dior-ganodichlorosilanes, especially pFl of the medium, are essential for cycli-sation. As pFl increases, i.e. the acidity of the medium decreases, the process of ring formation can be reduced but cannot be completely avoided. 

Raw stock organochlorosilanes methyltrichlorosilane, dimethyldichlo-rosilane, methylphenyldichlorosilane or phenyltrichlorosilane with the main substance content of at least 99.0-99.8% toluene (the boiling point is 109.5-111 °C, d420 = 0.865 0.002) butyl alcohol (the boiling point is 115-118 °C) polyester, the product of the polycondensation of ethylene glycol with phthalic and maleic anhydride ... 

Raw stock dimethyldichlorosilane (at least 99% of the main fraction) methylphenyldichlorosilane (at least 98% of the main fraction) di-phenyldichlorosilane (at least 98% of the main fraction) methyldichlorosi-lane (at least 98% of the main fraction) vinylmethyldichlorosilane (at least 99.6% of the main fraction) phenyldichlorosilane (at least 99% of the main fraction) phenyltrichlorosilane (at least 99% of the main fraction), toluene (coal or oil). 

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