Degussa Aktiengesellschaft

Evonik Degussa Gmbh

Martin Moerters

Kai Schumacher

Uwe Diener

Roland Schilling

Oswin Klotz

Helmut Mangold

Christoph Batz-Sohn

Stipan Katusic

Steffen Hasenzahl

Rainer Golchert

Monika Oswald

Heinz Lach

Guido Zimmermann

Gerrit Schneider

Harald Alff

Ina Hemme

Matthias Schmitt

Hauke Jacobsen

Juergen Flesch

Volker Hamm

Herbert Habermann

Horst Miess

Marcus Von Twistern

Andreas Schild

Witold Katerinak

Fumed silicon dioxide powder with a BET surface area of 20 to 35 m/g, characterized in that a) the number-based median particle diameter is 60 to 150 nm, and b) the proportion of particles with a diameter of 200 nm or more is at most 10%, and c) the proportion of particles with a diameter of up to 60 nm is at most 20%, based in each case on the total number of particles.

Low-surface area fumed silicon dioxide powder

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

Aluminium oxide powder produced by flame hydrolysis and consisting of aggregates of primary particles, having a BET surface area of from 100 to 250 m/g, a dibutyl phthalate absorption of from 50 to 450 g/100 g of aluminium oxide powder, which powder shows only crystalline primary particles in high-resolution TEM pictures. It is prepared by vaporizing aluminium chloride, transferring the vapour by means of a carrier gas to a mixing chamber and, separately therefrom, supplying hydrogen, air (primary air), which may optionally be enriched with oxygen and/or may optionally be pre-heated, to the mixing chamber, then igniting the mixture of aluminium chloride vapour, hydrogen, air in a burner and burning the flame into a reaction chamber that is separated from the surrounding air, subsequently separating the solid material from the gaseous substances and then treating the solid material with steam and optionally with air, the discharge rate of the reaction mixture from the mixing chamber into the reaction chamber being at least 10 m/s, and the lambda value being from 1 to 10 and the gamma value being from 1 to 15. It can be used as an ink-absorbing substance in ink-jet media.

Aluminium oxide powder produced by flame hydrolysis and having a large surface area

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

Flame-hydrolytically produced titanium dioxide powder that is present in the form of aggregates of primary particles, and has a BET surface of 20 to 200 m&sup2;/g, a half width (HW) [nm] of the primary particle distribution of HW &equals; a&#xd7;BETf where a &equals; 670&#xd7;10&#x2212;9 m&sup3;/g and &#x2212;1.3 &le; f &le; &#x2212;1.0 and the proportion of particles with a diameter of more than 45 &mgr;m lies in a range from 0.0001 to 0.05 wt. %. The powder is produced by a process in which a titanium halide is vapourised at temperatures of less than 200&deg;C., the vapours are transferred to a mixing chamber by means of a carrier gas of defined moisture content and, separately from this, hydrogen, primary air, which may optionally be enriched with oxygen and/or preheated, and steam are added to the mixing chamber, following which the reaction mixture is combusted in a reaction chamber sealed from the ambient air, secondary air is in addition introduced into the reaction chamber, the solid is then separated from gaseous substances, and following this the solid is treated with steam. The titanium dioxide powder may be used for the heat stabilisation of polymers.

Flame-hydrolytically produced titanium dioxide powder

Pyrogenically produced silica powder with a BET surface of 30 to 90 m/g, a dibutyl phthalate number of at least 80 and a tamped density of no more than 110 g/l. It is produced in that at least one vaporous silicon compound, a gas containing free oxygen and a combustible gas are mixed together in a closed burner and then burnt in a flame in the flame tube of the burner, the solid obtained is separated from the gas mixture and optionally purified, wherein the oxygen content of the gas containing free oxygen is adjusted such that the lambda value is greater than or equal to 1, and the gamma value is between 1.2 and 1.8. It can be used in toner applications.

Pyrogenically produced silica

Silicon-titanium mixed oxide powder produced by flame hydrolysis, which consists of aggregates of primary particles, with a BET surface area of 90&#xb1;15 m/g, a titanium dioxide proportion of 50&#xb1;8 wt. % and an anatase/rutile ratio of 60:40 to 70:30. It is produced in that a mixture of silicon halide, titanium halide, hydrogen and primary air is ignited in a burner and the flame is burned into a reaction chamber closed off from the surrounding air, and secondary air and a gas, which increases the temperature in the reaction chamber by combustion and/or which slows down the cooling in the reaction chamber because of low heat transfer, are additionally introduced into the reaction chamber. It can be used in toner compositions.

Silicon-titanium mixed oxide powder produced by flame hydrolysis

A silicon-titanium mixed oxide powder contains aggregates of primary particles selected from amorphous silicon dioxide particles, crystalline titanium dioxide particles, and silicon-titanium mixed oxide particles each having an amorphous silicon dioxide fraction and a crystalline titanium dioxide fraction. The silicon-titanium mixed oxide particles predominate in the powder. The powder exhibits a BET surface area of from 20 to 200 m/g, and a titanium dioxide content in a range of from greater than 10 wt. % to less than 70 wt. %. An X-ray diffractogram of the powder exhibits the diffraction patterns of rutile and anatase, with a rutile/anatase ratio of from 2:98 to 98:2. The powder can be produced by vaporizing a silicon halide and a titanium halide at temperatures of less than 180&#xb0; C., performing combustion with hydrogen and air in a reaction chamber that is closed off from the earth's atmosphere, separating the solids from gaseous substances, and subsequently removing halide-containing substances from the solids to the greatest possible extent by treatment with steam at temperatures of from 250 to 700&#xb0; C. The powder can be used in toners.

Silicon-titanium mixed oxide powder

Silicon-titanium mixed oxide powder prepared by flame hydrolysis, having a ratio by weight of silicon dioxide/titanium dioxide, which is greater on the surface of the primary particles than that within the total primary particle. It is prepared by a flame hydrolysis process, in that a stream consisting of a vaporous titanium dioxide precursor and oxygen or an oxygen-containing gas and hydrogen, and a second stream consisting of a vaporous silicon dioxide precursor and a carrier gas consisting of oxygen, an oxygen-containing gas and/or an inert gas, are guided separately into the reaction chamber of a burner such as is known for the preparation of pyrogenic oxides, and are burnt here, the solid mixed oxide powder and hot gases are subsequently cooled, and the gases are separated from the solid. The powder may be used, for example, for the preparation of sunscreen preparations.

Silicon-titanium mixed oxide powder prepared by flame hydrolysis, which is surface-enriched with silicon dioxide, and the preparation and the use thereof

Growing community of inventors

Rheinfelden, Germany

Martin Moerters