Abstract: Particulate silica is prepared by feeding a gas mixture of an organohalosilane gas, a flammable gas capable of generating water vapor when burned, and a free oxygen-containing gas to a reaction chamber through a multiple-tube burner, whereby the organohalosilane is subjected to flame hydrolysis and oxidation reaction. The amount of the flammable gas fed is 0.5-9 mol per mol of the organohalosilane and such that the amount of water vapor resulting from combustion of the flammable gas is 1-6 times the stoichiometric amount, and the gas mixture is fed to the center tube of the burner such that it may have a linear velocity at the outlet of 50-120 m/sec, calculated in the standard state. The resulting silica has a surface area of 100-400 m2/g and a narrow particle size distribution of primary particles and ensures the transparency of silicone rubber filled therewith.

Abstract: When oganohalosilanes are prepared by charging a reactor with a contact mass containing a metallic silicon powder, a copper catalyst and a co-catalyst, and introducing an organohalide-containing gas into the reactor to effect the direct reaction, the catalyst and/or co-catalyst used in the contact mass is obtained by mixing particles of the catalyst and/or co-catalyst with finely divided silica, and applying shear forces to the mixture for mutually rubbing the particles, thereby producing the catalyst and/or co-catalyst having finely divided silica fused to surfaces thereof. The invention is successful in producing organohalosilanes at a significantly improved formation rate without reducing the proportion of diorganodihalosilane.

Abstract: When oganohalosilanes are prepared by charging a reactor with a contact mass containing a metallic silicon powder, a copper catalyst and a co-catalyst, and introducing an organohalide-containing gas into the reactor to effect the direct reaction, the catalyst and/or co-catalyst used in the contact mass is obtained by mixing particles of the catalyst and/or co-catalyst with finely divided silica, and applying shear forces to the mixture for mutually rubbing the particles, thereby producing the catalyst and/or co-catalyst having finely divided silica fused to surfaces thereof. The invention is successful in producing organohalosilanes at a significantly improved formation rate without reducing the proportion of diorganodihalosilane.

Abstract: Spherical silica powder is produced by feeding silica powder having an average particle size of 0.3-40 &mgr;m to a burner flame formed with a flammable gas so as to continuously melt and spheroidize the particles within the flame. The use of a non-halogenated siloxane and/or alkoxysilane as an auxiliary flame-generating source raises the flame temperature and increases the length of the composite flame formed by combustion of the fuel gas with the siloxane or alkoxysilane. Moreover, the fine particles of silica that form as a result of siloxane or alkoxysilane combustion unite and coalesce with the particles of starting silica. These effects accelerate melting and spheroidization of the starting silica powder, resulting in thermally efficient and cost-effective spherical silica powder production.

Abstract: Spherical, non-crystalline silica particles made by burning a non-halogenated siloxane starting material are substantially halogen-free, and have a content of metallic impurities other than silicon of not more than 1 ppm, a particle size of 10 nm to 10 &mgr;m and a specific surface area of 3-300 m2/g. Production of the particles is carried out by oxidative combustion of the non-halogenated siloxane in a flame at a high adiabatic flame temperature to effect the formation of a large number of core particles and promote their coalescence and growth.

Abstract: Organohalosilanes are prepared by reacting an organic halide with metallic silicon particles in the presence of a metallic copper catalyst which is a metallic copper powder in flake form having a bulk specific gravity of 1-3 g/cm3 and a mean particle size of 10 &mgr;m to 1 mm as measured by laser diffraction particle size distribution analysis.

Abstract: Spherical silica powder is produced by feeding silica powder having an average particle size of 0.3-40 &mgr;m to a burner flame formed with a flammable gas so as to continuously melt and spheroidize the particles within the flame. The use of a non-halogenated siloxane and/or alkoxysilane as an auxiliary flame-generating source raises the flame temperature and increases the length of the composite flame formed by combustion of the fuel gas with the siloxane or alkoxysilane. Moreover, the fine particles of silica that form as a result of siloxane or alkoxysilane combustion unite and coalesce with the particles of starting silica. These effects accelerate melting and spheroidization of the starting silica powder, resulting in thermally efficient and cost-effective spherical silica powder production.

Abstract: Hydrophobic silica fine powder is produced by pyrolyzing a silane compound to form a silica fine powder and hydrophobizing the silica fine powder with an organohalosilane as hydrophobizing agent in a fluidization vessel. A portion of the silica fine powder is bypassed to a waste gas line from the fluidization vessel and collected with a cyclone and bag filter, and the collected powder is fed to the fluidization vessel where it is hydrophobized. The amount of unreacted organohalosilane in the waste gases is reduced, alleviating the burden on waste gas treatment. The silica having the unreacted organohalosilane borne thereon is fed back to the fluidization vessel, increasing the reaction efficiency of organohalosilane.

Abstract: Hydrophobic silica fine powder is prepared by pyrolyzing a silane compound to give silica fine powder, then treating the silica fine powder with a hydrophobizing agent in a fluidization vessel containing at most 3 vol % of oxygen. The process effectively confers the pyrogenic silica with hydrophobicity.

Abstract: Silicon oxide containing active silicon represented by the general formula: SiOx wherein x is from 0.8 to 1.9, when analyzed by solid state NMR (29Si DD/MAS) with a sufficient relaxation time set, exhibits a spectrum having two separate peaks, a broad peak (A1) centered at −70 ppm and a broad peak (A2) centered at −110 ppm, the area ratio A1/A2 being in the range of 0.1≦A1/A2≦1.0.

Abstract: A silicon oxide powder can be continuously prepared by feeding a raw material powder mixture containing silicon dioxide powder into a reaction chamber (2) at a temperature of 1,100-1,600° C., to produce a silicon oxide gas, transferring the silicon oxide gas to a deposition chamber (11) through a transfer conduit (10) maintained at a temperature of from higher than 1,000° C. to 1,300° C., causing silicon oxide to deposit on a substrate (13) which is disposed and cooled in the deposition chamber, scraping the silicon oxide deposit, and recovering the deposit in a recovery chamber (18). The method and apparatus is capable of continuous and stable production of amorphous silicon oxide powder of high purity.

Abstract: When oganohalosilanes are prepared by charging a reactor with a contact mass containing a metallic silicon powder and a copper catalyst, and introducing an organohalide-containing gas into the reactor to effect the direct reaction, a poly(organo)phosphino compound is added to the contact mass. The invention is successful in producing organohalosilanes at a significantly improved production rate without reducing the selectivity of useful silane.

Abstract: Organohalosilanes are prepared by the Rochow process of reacting metallic silicon particles with an organohalide in the presence of a copper catalyst. The metallic silicon particles, which are prepared by committing fragments of metallic silicon raw material, have a mean particle size of 10 &mgr;m to 10 mm and a surface oxygen quantity of at least 0.05 wt % and/or at least 0.001 g of oxygen/m2 of silicon surface area, which is given as the difference between the oxygen concentrations determined by in-metal oxygen analysis of the metallic silicon particles and the fragments, respectively. On analysis, the metallic silicon particles have been held for at least 3 hours in an air atmosphere at 25° C.

Abstract: Organohalosilanes are prepared by the Rochow process of reacting metallic silicon particles with an organohalide in the presence of a copper catalyst. The metallic silicon particles, which are prepared by comminuting fragments of metallic silicon raw material, have a mean particle size of 10 &mgr;m to 10 mm and a surface oxygen quantity of up to 0.3 wt % which is given as the difference between the oxygen concentrations determined by in-metal oxygen analysis of the metallic silicon particles and the fragments, respectively.

Abstract: When oganohalosilanes are prepared by charging a reactor with a contact mass containing a metallic silicon powder and a copper catalyst, and introducing an organohalide-containing gas into the reactor to effect the direct reaction, a metal complex of an organophosphino compound is added to the contact mass. The invention is successful in producing organohalosilanes at a significantly improved production rate without reducing the selectivity of useful silane.

Abstract: A contact mass for use in the synthesis of organohalosilanes is prepared by adding metallic copper particles to metallic silicon particles, and rubbing the particles against each other under high shear forces in a non-oxidizing atmosphere, thereby forming a metallic copper thin film on the surface of the metallic silicon particles in a spot pattern or entirely. The contact mass is capable of reducing the time required for activation and has an extended lifetime.

Abstract: Crude fumed silica resulting from pyrogenic hydrolysis is purified by continuously feeding particulate silica and steam or a mixture of steam and air in a steam/air volume ratio of at least 1/2 through an upright column from its bottom toward its top for forming a fluidized bed within the column at a gas linear velocity of 1 to 10 cm/sec. and a temperature of 250.degree. to 400.degree. C., whereby steam deprives the particulate silica of the halide borne thereon, and removing fine particulate silica from which the halide has been eliminated from the top of the column. Using a simple apparatus, pure fine particulate silica is collected at a low cost of energy consumption.

Abstract: A service area expansion scheme for a mobile communication system, capable of efficiently connecting thinly populated areas (satellite zones) to a mobile communication network so as to expand the service area of the mobile communication system economically. In expanding the service area, remote base stations are set at thinly populated areas, while a remote mobile local switching station for connecting the remote base stations to the mobile communication network is provided. The remote base stations and the remote mobile local switching station are selectively connected through the public network by using the respective channel connection units for providing connections with the public network. The remote base stations and the remote mobile local switching station can be replaced by satellite base stations and a satellite mobile local switching station for connecting the satellite base stations to the mobile communication network.

Abstract: A process to prevent scale adhesion on rector surfaces when polymerizing vinyl esters, vinyl esthers, carboxylic acids, styrene or diene monomers. Coating of internal reactor surfaces with a combination of an amino containing aromatic compound, and an alkali metal or ammonium salt of polyvinylsulfuric acid results in the scale prevention. This combination is applied to reactor surfaces via its mixture with a solvent and is subsequently dried to form the coating.

Abstract: A process to prevent scale adhesion on reactor surfaces when polymerizing vinyl monomers. Coating of internal reactor surfaces with a combination of an amino containing aromatic compound, and an alkali metal or ammonium salt of polyvinylsulfuric acid results in the scale prevention. This combination is applied to reactor surfaces via its mixture with a solvent and is subsequently dried to form the coating.