Abstract: Pyrogenically produced silica powder with a BET surface of 30 to 90 m2/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.

Abstract: Pyrogenically produced silicon dioxide powder in the form of aggregates of primary particles having a BET surface area of 90±15 m2/g, wherein the aggregates display an average surface area of 10000 to 20000 nm2, an average equivalent circle diameter (ECD) of 90 to 130 nm and an average circumference of 1000 to 1400 nm. It is produced by a pyrogenic process in which silicon tetrachloride and a second silicon component comprising H3SiCl, H2SiCl2, HSiCl3, CH3SiCl3, (CH3)2SiCl2, (CH3)3SiCl and/or (n-C3H7)SiCl3 are mixed with primary air and a combustion gas and burnt into a reaction chamber, secondary air also being introduced into the reaction chamber, and the feed materials being chosen such that an adiabatic flame temperature of 1810 to 1890° C. is obtained. Dispersion containing the pyrogenically produced silicon dioxide powder.

Abstract: High-purity pyrogenically prepared silicon dioxide having metal contents of less than 9 ppm is prepared by reacting a silicon tetrachloride having a metal content of less than 30 ppb by means of flame hydrolysis. The silicon dioxide can be utilized for the manufacture of high-purity glasses by means of the sol-gel process, which show a high-homogenity. It can be used for the production of shaped articles, which can be used as performs for the optical fiber spinning.

Abstract: Pyrogenically produced silicon dioxide powder in the form of aggregates of primary particles having a BET surface area of 90±15 m2/g, wherein the aggregates display an average surface area of 10000 to 20000 nm2, an average equivalent circle diameter (ECD) of 90 to 130 nm and an average circumference of 1000 to 1400 nm. It is produced by a pyrogenic process in which silicon tetrachloride and a second silicon component comprising H3SiCl, H2SiCl2, HSiCl3, CH3SiCl3, (CH3)2SiCl2, (CH3)3SiCl and/or (n-C3H7)SiCl3 are mixed with primary air and a combustion gas and burnt into a reaction chamber, secondary air also being introduced into the reaction chamber, and the feed materials being chosen such that an adiabatic flame temperature of 1810 to 1890° C. is obtained. Dispersion containing the pyrogenically produced silicon dioxide powder.

Abstract: Pyrogenically produced silica powder with a BET surface of 30: to 90 m2/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 die lambda value is greater than or equal to 1, and die gamma value is between 1.2 and 1.8. It can be used in toner applications.

Abstract: The invention relates to spherical colored pigments having an average particle diameter of less than 10 .mu.m on the basis of an oxide, a mixed oxide or a silicate. The pigments are obtainable by means of spray-pyrolysis technology: a solution containing oxide-forming or silicate-forming metal compounds is converted into an aerosol and the latter is fed, preferably after predrying, to a pyrolysis reactor; the pigment is separated from the pyrolysis gas. The colored pigments according to the invention are suitable for the production of ceramic decorations and for the coloring of plastics, synthetic foils, fibers and also lacquers. By reason of the spherical shape, unusual technical application properties are achieved.

Abstract: The invention relates to pigments consisting of substantially spherical particles with a mean particle diameter of less than 10 .mu.m, on the basis of an oxidic or silicate substrate material with noble metal distributed extremely finely on and/or in the particles. Preferred pigments are purple-colored and are based on an oxide from the series SiO.sub.2, SnO.sub.2 and ZrO.sub.2 and gold as noble metal. The pigments are suitable for the production of ceramic decorations and for the dyeing of plastics, synthetic films and fibers as well as lacquers. Exceptional application properties are obtained by virtue of the spherical shape. The pigments are obtainable by a spray-pyrolysis process in which an aerosol consisting of a solution of at least one noble metal compound and an oxide- or silicate-forming precursor is subjected to pyrolysis; the pigment is separated from the pyrolysis gas.

Abstract: Silica with the following physico-chemical properties:______________________________________ Specific surface m.sup.2 /g 80-400 Primary particle size nm 7-40 Tapped density g/l 50-300 pH value 3-10 Carbon content % 0.1-15 DBP number % <200 ______________________________________is produced by spraying a silica under intensive mixing, optionally with water or dilute acid at first and then with a surface-modifying reagent or a mixture of several surface-modifying reagents, then mixing, tempering, and subsequently destructuring/compressing and grinding.

Abstract: In order to produce precious metal powders of uniform particle size and low BET specific surface, appropriate aerosols are introduced into a flame reactor, whereby the aerosols are first freed of solvent as completely as possible by a thermal treatment.

Abstract: A process for the production of 2,2'-bis(4-hydroxyphenyl)propanes by reacting the corresponding phenols and carbonyl compounds in the presence of organopolysiloxanes containing sulphonate and mercapto groups and acting as a catalyst, consisting of units of the formula?O.sub.3/2 --Si--R.sup.1 --SO.sub.3 --!.sub.x M.sup.x+ (I),wherein R.sup.1 is a linear or branched alkylene group having 1 to 12 C atoms, a cycloalkylene group having 5 to 8 C atoms or a unit of the formulae ##STR1## and units of the formulaO.sub.3/2 --Si--R.sup.