MACROKINETICS OF HYDROLYTIC POLYCONDENSAT ION OF ORGANOCHLOROSILANES (REVIEW)

This work is a first publication summarizing the results of studies of the effect of macroscopical factors on the direction of hydro;lytic p olycondensation of organochlorosilanes and the composition of products . We included in this review the results of investigation of macrokine tics of the process in question and the published data from which nece ssary information can be obtained. The effect of such factors as inten sity of mixing of the components of reaction system, the order in whic h the reagents are introduced, phase and aggregative states of the rea ction system are considered. The review also contains information on t he following questions: determination of the reacting phase and the zo ne in which the reaction occurs, finding the sections of conode lines corresponding to phase quasi-equilibrium, first results of numerical a nalysis (UNIFAC method) of the problem of quasi-equilibrium between th e phases. In the initial stages, the reaction of hydrolytic polyconden sation of organochlorosilanes is heterogeneous as it follows from the limited mutual solubility of water and or- ganochlorosilanes. Under th ese conditions, in those parts of the reaction system which contain or ganic components and also at the interfacial boundary, the reaction pr oceeds via the mechanism of partial. hydrolysis. It was shown that in this case the growth of siloxane chains begins as reaction of heterofu nctional polycondensation of organochlorosilanes and products of hydro lysis. Therefore, the reaction of heterofunctional polycondensation is the main mechanism which determines the composition of products forme d at the initial stages of the reaction of hydrolytic polycondensation of organochlorosilanes. The extent of this reaction is the main param eter in terms of which one can describe formation df organosilanols, o rganocyclosiloxanes, branched organopolysiloxanes, as well as gel form ation.