Autocatalytic synthesis of silicones

According to the data provided in the literature and to the results of experiments and calculations using the NRTL and UNIFAC equations, hydrolytic polycondensation of silicone monomers R_nSiX_4−n (X = Cl; —OR′, —OCOR) is an autocatalytic process that is accelerated by the products of the process (silanols, alcohols, acids) owing to their effect on the increase in solubility and, as a consequence, on the increase in the concentration of the reagent (water) in the reaction zone. This is also facilitated by an increase in both the intensity of mixing of reagents and temperature. Modeling of changing phase quasi-equilibria during the hydrolysis of silicone monomers showed that in the kinetic regime, the supply of water from the aqueous phase exceeds its consumption in the reaction, which leads to an increase in the rate of hydrolysis. The autocatalytic nature of the hydrolysis and condensation of alkoxy- and acetoxysilanes offers prospects for the catalyst- and solvent-free synthesis of polyorganosiloxanes.