Hydrophobic filler mixtures, process for its production and use

摘要

There is produced a hydrophobic mixture for RTV and LTV silicone rubber by applying a hydrophobizing agent to a precipitated silica, homogeneously mixing this powdery concentrate into a pyrogenically produced silica, tempering the mixture and mechanically compacting. The hydrophobic filler mixture obtained in the untempered condition consists of: Pyrogenically produced silica: 50 to 85 weight % Precipitated silica: 5 to 40 weight % (e.g. 5 to 30 weight %) Hydrophobization agent: 8 to 30 weight % Aluminum oxide: 0.5 to 5 weight %.