Abstract: A process for preparing hydrophobic finely divided particles of oxides of metals and/or oxides of silicon by chemically bonding hydrocarbon radicals to the surface of the oxide particles, said process comprising intensively mixing oxide particles having a water content less than about 1% by weight with a hydrolizable metal or metalloid compound containing OR groups, wherein said compound is an ester of the general formula:Me(OR).sub.4wherein Me is an element from group IV of the periodic table, and each R is independently selected from C.sub.1 -C.sub.8 alkyl radicals or an aryl radical. A hydrophobic silicon dioxide particle is provided. Particles prepared by the process are useful as fillers in elastomers.

Abstract: A process for preparing hydrophobic finely divided particles of oxides of metals and/or oxides of silicon by chemically bonding hydrocarbon radicals to the surface of the oxide particles, said process comprising intensively mixing oxide particles having a water content less than about 1% by weight with a hydrolyzable metal or metalloid compound containing OR groups, wherein said compound is an ester of the general formula:Me(OR).sub.4wherein Me is an element from group IV of the periodic table, and each R is independently selected from C.sub.1 -C.sub.8 alkyl radicals or an aryl radical. A hydrophobic silicon dioxide particle is provided. Particles prepared by the process are useful as fillers in elastomers.

Abstract: A highly active superdry silica aerogel free of adsorbed water and hydrogen-bonded silanol groups the infrared spectrum of which is characterized by a single narrow intense band at about 3700 cm.sup..sup.-1 within the range between 4000 and 2000 cm.sup..sup.-1 indicating the presence of free silanol groups and which spectrum is further characterized by the absence of bonds indicating the presence of adsorbed water and hydrogen-bonded silanol groups, the said silica aerogel having been produced by subjecting a pyrolytically produced silica aerogel containing adsorbed water and both free and hydrogen-bonded silanol groups to treatment in a fluidized bed at a temperature between about 700.degree. and 1000.degree. C and at a pressure between 2 torrs and atmospheric pressure for a period between 1 second and a few minutes through which fluidized bed a stream of a dried gas that had been preheated to a temperature between 100.degree. and 300.degree. C was passed.

Abstract: An apparatus for making particulate materials hydrophobic has means for activating the material, means for charging the material with a substance capable of imparting hydrophobic characteristics thereto, means for causing reaction between the material and the substance with which it is charged and means for treating the material subsequent to the reaction so as to remove excess of the substance therefrom.

Abstract: Highly dispersed metal or metalloid oxides are rendered hydrophobic byI. contacting such oxide particles while in the form of an aerogel with a dry inert gas stream in a fluidizing bed at a temperature from 600.degree. to 1000.degree. C and at atmospheric pressure for a period of less than 60 seconds to render the particles absolutely dry and thus activate them;Ii. charging the resultant dried and activated particles in a fluidizing bed with at least one gas-phase organosilicon compound selected from the group consisting of (a) linear organopolysiloxanes (b) cyclic organopolysiloxanes (c) a mixture of both types of siloxanes and (d) a mixture of any of the substances (a)-(c) with an organohalogenosilane at a temperature in the range from 25.degree. to 650.degree. C;Iii. causing said charged particles to react with the organosilicon compounds at a temperature from 35.degree. to 650.degree. C; andIv. finally treating the reaction product with an inert gas stream in a fluidizing bed at temperatures from 500.

Abstract: A process for preparing hydrophobic finely divided oxides of metals and/or oxides of silicon comprising activating finely divided particles of oxides of metals and/or oxides of silicon by heating the particles at about 700.degree. - 1000.degree.C for less than about 60 seconds in a stream of inert gas to substantially completely free the particles of not only the physically bonded, but also the chemically bonded water, and contacting the activated particles with at least one organosilicon compound and substantially anhydrous ammonia gas for less than about 60 seconds. The hydrophobic products are useful as fillers in elastomers.