HYDROPHOBIC PRECIPITATED SILICIC ACID* METHOD OF MAKING SAME AND HARDENABLE ELASTOMER COMPOSITION INCLUDING SAME AS REINFORCING FILLER

摘要

The silica has the following properties: BET-surface m<2>/g 110+/-40 average primary particles size from EM photographs nm 15-22 drying loss according to DIN 921 after 2 hours at 105 DEG C % 2.5 ignition loss (based on the substance dried for 2 hours at 105 DEG C) according to DIN 55 921 %5.5+/-1.5 pH-value (in 5 % aqueous-methanolic suspension) according to DIN 53 200 7.5+/-1.0 conductivity (in 4% aqueous-methanolic suspension) mu S <600 bulk density of the unventilated substance according to DIN 53 194 g/l 130+/-40 wettability with water <0.1 carbon content % 2.5+/-0.6 water uptake at 30 DEG C % relative humidity % 1.2+/-0.4 at 30 DEG C/70 % relative humidity % 1.5+/-0.5. A process for the production of such a silica is disclosed. The silica is used as a reinforcing filler in diorganopolysiloxane-based compositions hardenable to form elastomers, particularly in one-component silicon rubber joint-sealing compounds and silicon rubber sheathing compounds.