Degussa Aktiengesellschaft

Evonik Degussa Gmbh

Dequssa Ag

Gerrit Schneider

Monika Oswald

Klaus Deller

Helmut Mangold

Heinz Lach

Christoph Batz-Sohn

Wolfgang Lortz

Werner Will

Gabriele Perlet

Rolf Clasen

Thomas Scharfe

Jürgen Meyer

Kai Schumacher

Martin Moerters

Markus Hornfeck

Christine Wagner

Christoph Batz-sohn

Martin MÖRTERS

Process for the production of an aqueous dispersion of pyrogenically produced metal oxide and metalloid oxide powders with a BET surface area of between 5 and 600 m/g, with a metal oxide or metalloid oxide content in the dispersion of between 5 and 25 wt. %, comprising the following steps:

Process for the production of metal oxide and metalloid oxide dispersions

A dispersion containing a high-surface-area, pyrogenically-produced aluminium oxide with a surface area and BET of more than 115 m/g and a Sears number of more than 8 ml/2 g, is produced by mixing a high-surface-area, pyrogenically-produced aluminium oxide having a BET specific surface area of more than 115 m/g and a Sears number of more than 8 ml/2 g, with water, setting a pH value of 2 to 11 (preferably 3 to 8) and dispersing the mixture by the introduction of controlled shearing forces. It can be used for the production of Inkjet media, digital imaging products and other printing medium.

Dispersion of aluminium oxide

Pyrogenic silicon dioxide powder with a BET surface area of 30 to 90 m/g, a DBP index of 80 or less, a mean aggregate area of less than 25000 nmand a mean aggregate circumference of less than 1000 nm, wherein at least 70% of the aggregates have a circumference of less than 1300 nm. It is prepared by mixing at least one silicon compound in vapor form, a free-oxygen-containing gas and a combustible gas in a burner of known construction, igniting this gas mixture at the mouth of the burner and burning it in the flame tube of the burner, separating the solid obtained from the gas mixture and optionally purifying, wherein the oxygen content of the free-oxygen-containing gas is adjusted so that the lambda value is greater than or equal to 1, the gamma value is between 1.2 and 1.8, the throughput is between 0.1 and 0.3 kg SiO/mof core gas mixture and the mean normalized rate of flow of gas in the flame tube at the level of the mouth of the burner is at least 5 m/s. The powder can be used as a filler. A dispersion containing the powder according to the invention. The powder can be used as a filler in rubber, silicone rubber and plastics. The dispersion can be used to prepare glass items.

Pyrogenic silicon dioxide and a dispersion thereof

Aqueous dispersions of a pyrogenically-produced aluminum oxide are prepared form a mixture containing water, additives and a high-surface-area pyrogenically-produced aluminum oxide with a BET specific surface area of more than 115 m/g and a Sears number of more than 8 ml/2 g using controlled high shearing conditions. Prior to subjecting the mixture to high shear conditions, the pH of the mixture is adjusted to a value between of 2 to 11 (preferably 3 to 8). The aqueous dispersion has a mean particle size distribution of d&#x3c;150 nm. These dispersions are useful in the production of Inkjet media, digital imaging products and other printing media and result in high color densities, photo-realistic reproductions and particularly good print and gloss quality.

An aqueous dispersion, having a silicon dioxide powder having a silicon dioxide content of 10 to 60 wt.%, wherein the aqueous dispersion is stable in the pH range of 2 to 6, the aqueous dispersion additionally contains at least one compound, which is at least partially soluble in aqueous solution in the pH range 2 to 6 in the form of polyvalent cations, these being stable in a silicate-like environment as an anionic component of the particle surface of the silicon dioxide powder, the quantity of cation-providing compound in relation to the surface of the silicon dioxide is 0.001 to 0.1 mg cation-providing compound/msilicon dioxide surface, the cation-providing compound being calculated as the oxide, and the zeta potential of the aqueous dispersion has values of less than or equal to zero.

Stabilized, aqueous silicon dioxide dispersion

A method for producing ultra-high purity, optical quality, glass articles is disclosed which involves:

Method for producing ultra-high purity, optical quality glass articles

Pyrogenically prepared silicon dioxide with the following physicochemical properties:

Glass prepared from pyrogenically prepared silicon dioxide

Aqueous dispersion comprising silicon/titanium mixed oxide powder with a BET surface area of 5 to 500 m/g which has been prepared by flame hydrolysis and has a titanium dioxide content of 0.5 to 20 wt. %, based on the powder, water and at least one pH-regulating substance which can be removed completely from the reaction mixture on heating, the aqueous dispersion having a solids content of between 40 and 80 wt. %. A green body produced therefrom with a green density of between 40 and 85%. A shaped glass article of optical quality with a coefficient of thermal expansion of not more than 0.5&#xd7;10/K produced from the green body.

Dispersion comprising silicon/titanium mixed oxide powder, and green bodies and shaped glass articles produced therefrom

SiO &mdash;TiO glasses having a low coefficient of thermal expansion are produced by a molding being produced that consists of SiO powder, SiO &mdash;TiO powder or TiO powder and that contains by way of secondary component a titanium-containing component which is converted into amorphous TiO .

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Hanau, Germany

Gerrit Schneider