Registration Dossier
Registration Dossier
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EC number: 242-560-0 | CAS number: 18765-38-3
Endpoint summary
Administrative data
Description of key information
Additional information
Tetrakis(2-butoxyethyl) orthosilicate is a liquid at standard temperature and pressure, with a melting point of <-100°C, and a boiling point of 370.0°C. It has a measured relative density of 0.966 at 20°C and a vapour pressure of 0.0018 hPa at 20°C.
The substance is not classified for flammability according to Regulation (EC) No. 1272/2008 on the basis of a measured flash point >110°C and a boiling point of 370.0°C. It has a measured auto-ignition temperature of 315°C, and is not explosive and not oxidising on the basis of chemical structure.
In contact with water tetrakis(2-butoxyethyl) orthosilicate reacts rapidly (half-life of approximately 4 hours at pH 7, 1.7 hours at pH 4, 1.7 hours at pH 9 and 20 -25°C) to monosilicic acid and 2-butoxyethanol according to the following equation:
Si(OCH2CH2OCH2CH2CH2CH3)4+ 4H2O → Si(OH)4 + 4CH3CH2CH2CH2OCH2CH2OH
Therefore, the properties of the hydrolysis products monosilicic acid and 2-butoxyethanol have been obtained.
The silanol hydrolysis product, silicic acid, has an calculated water solubility of 1.0E+06 mg/l. However,at concentrations above about 100-150 mg/l (measured as SiO2 equivalents), condensation products of monosilicic acid can also form. At concentrations >100-150 mg/l of SiO2, monomeric monosilicic acid condenses into colloidal particles of polysilicic acid (silica sol) or a highly cross-linked network (silica gel). The condensation rate is dependent on temperature, concentration, and acidity/alkalinity (as in the pH) of the system. A dynamic equilibrium is established between monomeric monosilicic acid, oligomers and insoluble amorphous polysilicic acid.
A vapour pressure of <1E-06 Pa at 25°C, and a log Kowvalue of -4 were determined for monosilicic acid using QSAR methods.
2-Butoxyethanol is miscible with water, has a log Kow value of 0.81 and a vapour pressure of 117 Pa at 25°C.
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