MECHANISM OF THE HETEROPHASE HYDROLYSIS OF METHYLPHENYLDIMETHOXYSILANE

The initial stages of methylphenyldimethoxysilane hydrolysis in acetone were investigated. The boundaries of diffusion and kinetic areas of the process were defined. Methylphenyldimethoxysilane hydrolysis proceeds to kinetic mode at a lower mixing intensity than methylphenyldichlorosilane hydrolysis does. The constant of methylphenyldimethoxysilane hydrolysis rate (Kh = 0.5×10^-3 s^-1 ) was found. Unlike methylphenyldichlorosilane hydrolysis, methylphenyldimethoхysilane hydrolysis products composition is independent of the concentration of acetone. This fact indicates a low selectivity of the process. The part of oligomeric products is quite large. Homocondensation is supposed to make a greater contribution to the formation of methylphenyloligoorganosiloxanes than heterocondensation does. The presence of methylphenyldimethoxysilane hydrolysis products depending on water-methylphenyldimethoxysilane ratio shows that the hydrolysis occurs in both phases of the system, and the main reaction zone is the organic phase.

hase equilibrium, hydrolysis, condensation, emulsive polycondensation, macrokinetics, superposed process, diagram Gibbs, area of passing process, organoalkoxysilanes.

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