Back to results
US 4,054,689 AGranted
Method of preparing hydrophobic silica
AssigneeThe Dow Chemical Company
InventorDonald William Calvin
Life of this patent
Estimating the term…
Abstract
Amorphous silica is rendered hydrophobic by treating the silica with hydrogen fluoride vapors. The hydrophobic silica thus produced is useful in applications wherein either the sorbed fluoride values are desired or else the hydrophobic properties are desired. The hydrophobic properties are overcome by extended contact with water and the silica then becomes hydrophilic.
Claims7
A method of causing fine-particle silica to be hydrophobic, said method comprising
- providing a supply of substantially dry, fine-particle silica which is not hydrophobic and a supply of gaseous anhydrous HF or a gaseous HF stream containing water vapor,
- contacting the silica, in the substantial absence of liquid water, with the gaseous anhydrous HF or gaseous HF stream containing water vapor at a temperature above the dew point of the HF and the water vapor, when water vapor is present
- continuing said contacting until the amount of fluorine values sorbed by the silica is in the range of about 0.06 to about 2% by weight,
- discontinuing the supply of HF vapor being supplied to the silica, and
- recovering the so-formed hydrophobic silica.
2 more elements
Dependencies are inferred from the claim text.