Wacker-chemie Gmbh

Ernst Muhlhofer

Gunter Kratel

Peter Scherm

Gunter Stohr

Franz Schreiner

Wilfried Lang

Ludwig Eberle

Stephen Loskot

A process for continuously rendering finely divided, pyrogenic silica hydrophobic at low temperatures in the presence of a hydrophobicizing aid such as aliphatic alcohols having from 1 to 3 carbon atoms. The process of rendering silica hydrophobic is conducted at temperatures of from 60.degree. to 350.degree. C., and more preferably from 80.degree. to 150.degree. C., over a period of from 2 to 5 hours, and more preferably from 3 to 4 hours. The hydrophobicizing agents are known organohalosilanes and the preferred hydrophobicizing aid is methanol. The hydrophobicizing aid is used in amounts of from 2% to 15% by weight, and more preferably in amounts of from 2% to 10% by weight, based on the weight of silica used.

Hydrophobicization of pyrogenic silica

The invention relates to a process for continuously hydrophobicizing pyrogenic, finely divided silica, in which the waste gases are fed back to a mixing chamber upstream of the SiO.sub.2 reaction flame.

Process for hydrophobicizing of pyrogenic silica

A process for the production of pyrogenic silicic acid having an increased thickening effect which comprises subjecting silicon-containing materials to a pyrolysis flame while introducing additional energy into the flame. The invention also relates to the product so obtained, particularly useful for articles of dental care.

Process for producing pyrogenic silicic acid with increased thickening

A process for the manufacture of highly dispersed silicon dioxide with improved thickening action by treatment of pyrogenically produced silicic acid comprising the following steps:

Thickening agent for liquid media consisting of highly dispersed silicon

A process and device for the manufacture of highly disperse silicon dioxide by reacting gaseous organosilanes and other gases that burn with formation of water with oxygen-containing gases in a flame which comprises evaporating the organosilane in an evaporator in such a manner that the level of liquid organosilane is held constant at an organosilane evaporatinng vapor pressure of 0.2 to 1.2 atmospheres gage and, at most, at a temperature of 45.degree. C, preferably 20.degree. to 35.degree. C, above the boiling point of the particular organosilane, maintaining the temperature of the vapor until mixing with the other gases occurs, metering the gas mixture resulting from the mixing through a cone-shaped inlet into a combustion chamber, flushing oxygen-containing gases through an annular nozzle surrounding the inlet into the combustion chamber, and indirectly but positively, cooling the latter.

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Oschle, Germany

Ernst Muhlhofer