초록

Finely divided precipitated silicic acid is obtained by the method of the invention. Compositions containing the finely divided precipitated silicic acid as a filler distributed in an elastomer such as an organopolysiloxane are disclosed.

대표청구항 ▼

A process for the production of hydrophobic silicic acid comprising treating precipitated silicic acid having the following properties: ________________________________ -BET surface acc. to DIN 66 131 m2/g 150 ±30 Average size of the primary particles from EM pictures nm 15-22 Loss after drying acc.

A process for the production of hydrophobic silicic acid comprising treating precipitated silicic acid having the following properties: ________________________________ -BET surface acc. to DIN 66 131 m2/g 150 ±30 Average size of the primary particles from EM pictures nm 15-22 Loss after drying acc. to DIN 55 921 after 2 hours at 105°C. % 2.5-3.5 Loss at red heat (related to the substance dried for 2 hours at 105°C.) acc. to DIN 55 921 % 3 ±0.5 pH value (in 5% aqueous dis- persion) acc. to DIN 53 200 3.5-5.5 Conductivity (in 4% aqueous dispersion) us 3 content (related to the substance dried for 2 hours at 105°C.) % 2O content (related to the substance dried for 2 hours at 105°C.) % 10:0.5 to 10:3 and agitating the precipitated silicic acid with hydrophobic agent, and tempering the product obtained for 60 to 180 minutes at a temperature of 200°C. to 400°C. and thereafter grinding to form a finely divided product.