Evonik Degussa Gmbh

Degussa Aktiengesellschaft

Volker Hamm

Kai Schumacher

Juergen Flesch

Helmut Mangold

Martin Moerters

Harald Alff

Matthias Schmitt

Thomas Scharfe

Matthias Rochnia

Andreas Hille

Roland Schilling

Thomas Hennig

Peer Plambeck-Fischer

Marcus Von Twistern

Florian Felix Kneisel

Jürgen Flesch

Martin Mörters

Aluminum oxide powder in the form of aggregates of primary-particles, which has a BET surface area of from 10 to 90 m2/g and comprises as crystalline phases, in addition to gamma-aluminum oxide and/or theta-aluminum oxide, at least 30% of delta-aluminum oxide. It is prepared by vaporizing aluminum chloride and burning the vapor together with hydrogen and air, the ratio of primary air/secondary air being 0.01 to 2, the exit speed vof the reaction mixture from the burner being at least 10 m/s, the lambda value being 1 to 4, the gamma value being 1 to 3 and the value of gamma*v/lambda being greater than or equal to 55. Dispersion comprising the aluminum oxide powder. Coating composition comprising the dispersion.

Aluminium oxide powder, dispersion and coating composition

Provided is a pyrogenically prepared SiOpowder in the form of aggregated primary particles having a statistical thickness surface area (STSA) of 10-500 m/g, a thickening action based on the STSA of 4-8 mPas&#xb7;g/m, and a micropore volume of 0.03-0.07 cm/g, and a process for preparing the pyrogenic SiOpowder, which involves: introducing hydrolyzable silicon compounds, a primary gas comprising oxygen, and a primary combustion gas into a mixing chamber to produce a mixture; igniting the mixture in a burner to produce a flame, which is burned into a reaction chamber to produce the pyrogenic SiOpowder and gaseous substances; and separating the pyrogenic SiOpowder from the gaseous substances, wherein a ratio of the amount of primary combustion gas introduced to a stoichiometric amount of primary combustion gas required is referred to as gammaand has a value of less than 1, and wherein a ratio of the amount of primary gas comprising oxygen introduced to a stoichiometric amount of primary gas comprising oxygen required is referred to as lambdaand has a value of greater than 1.

Pyrogenically prepared silicon dioxide with a low thickening effect

Process for removing halide compounds adhering to finely divided metal oxide particles by means of steam, wherein the metal oxide particles are applied to the upper part of an upright column and migrate downwards by means of gravity, the steam is applied at the bottom end of the column, the metal oxide particles and the steam are fed counter-currently, the metal oxide particles freed of halide residues are removed at the base of the column, steam and halide residues are removed at the head of the column, wherein the column is heated in such a manner that the temperature difference T&#x2212;Tbetween the lower part and the upper part of the column is at least 20&#xb0; C. and a maximum temperature of 500&#xb0; C. prevails in the column, and the metal oxide particles have a residence time in the column of from 1 second to 30 minutes.

Purification of finely divided, pyrogenically prepared metal oxide particles

Pyrogenically produced aluminum oxide, in which the BET specific surface area is greater than 115 m /g and the Sears index is over 8 ml/2 g and the dibutyl phthalate absorption as a powder measured with a 16 g weighed portion is not measurable, is produced by means of flame oxidation or preferably flame hydrolysis, whereby a vaporizable aluminum compound is used as starting material. The aluminum oxide can be used as an ink-absorbing substance in inkjet media and also as a filler, as a substrate, as a catalytically active substance, as a starting material for the production of dispersions, as a polishing material (CMP applications), as a ceramic raw material, in the electronics industry, in the cosmetics industry, as an additive in the silicone and rubber industry, to adjust the rheology of liquid systems, as a heat stabilizer, in the paint industry.

Pyrogenically produced aluminum oxide

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Bad Saeckingen, Germany

Volker Hamm