US Patent 7842269 Pyrogenically prepared silicon dioxide compacted to give crusts

Pyrogenically prepared silicon dioxide is compacted to give crusts, in that it is subject to preliminary de-aeration, and is compacted to give crusts, and the crusts are broken and, if appropriate, classified. The tamped bulk density (to DIN EN ISO 787-11) of the silicon dioxide compacted to give crusts is from 185 to 700 g/l. It can be used as filler in rubber mixtures.