Oligomeric ethyl silicate

Dibutyltin diacetate, dilaurate, and di-(2-ethylhexanoate) are used as homogeneous catalysts for room-temperature-vulcanizing (RTV) silicones. The dialkyltin compounds bring about the cross-linking of the oligomeric siloxanes, to produce flexible, silicone rubbers having a host of different uses, such as electrical insulators and dental-impression molds. Recent work has also shown (560) that various dibutyltin dicar-boxylates catalyze both the hydrolysis and gelation of ethyl silicate under neutral conditions. 

Although tetraalkoxysilanes are usually applied as silica precursors in sol-gel procedures, the oligomeric type precursors can also be used instead. Ethyl silicate 40 (ES 40) is the most common commercial form of ethoxypolysiloxane available at prices competitive to those of TEOS/TMOS. Hence its application in the synthesis of composite adsorbents could be economically attractive provided that this would has little or no adverse effect on their final properties. The objective of this work was to test an alternative, cost-effective preparation procedure making use of the low-cost reagents ES 40 and 95wt% EtOH and to compare the properties of the adsorbents obtained with those of their counterparts similar in composition, yet synthesized with the use of TEOS. 

Silicate gels have also been synthesized using oligomeric precursors. Ethyl Silicate 40 is a commercial form of ethoxypolysiloxane (ethyl polysilicate) that results when the ethanol used in the production of TEOS contains some water (industrial spirit) (24). Water plus the hydrogen chloride by-product (Eq. 13) result in the partial hydrolysis and condensation of the... 

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