Precipitated silicic acid, method and compositions containing same

Claim 2

Hydrophobic silicic acid having the following properties: ______________________________________ BET surface acc. to DIN 66 131 m.sup.2 /g 110 ± 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 Loss at red heat (related to the substance dried for 2 hours at 105° C.) acc. to DIN 55 921 % 5.5 ± 1.5 pH value (in 5% aqueous dispersion) acc. to DIN 53 200 7 ± 1 Conductivity (in 4% aqueous dispersion) μS 600 Tamped density of the unaerated substance acc. to DIN 53 194 g/l 50 ± 20 Water wettability <0.05 Carbon content % 2.5 ± 0.6 Water absorption at 30° C. & 30% RM % 1.2 ± 0.4 at 30° C. & 70% % 1.5 ± 0.5 DBP adsorption % 260 ± 30 ______________________________________ said hydrophobic silicic acid having been prepared from a precipitated silicic acid by treating and agitating said silicic acid with a hydrophobic agent in a ratio of 10:0.5 to 10:3 followed by tempering for 60 to 180 minutes at a temperature of 200° C. to 400° C. and grinding to form a finely divided product, and said precipitated silicic acid having the following properties: ______________________________________ BET surface acc. to DIN 66 131 m.sup.2 /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 150° 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 dispersion) acc. to DIN 53 200 3.5-5.5 Conductivity (in 5% aqueous dispersion) μS <500 Tamped density of the unaerated substance acc. to DIN 53 194 g/l 60 ± 20 SO.sub.3 content (related to the substance dried for 2 hours at 105° C.) % <0.3 Na.sub.2 O content (related to the substance dried for 2 hours at 105° C.) % <0.3 ______________________________________

Claim 3

Hydrophobic silicic acid having the following properties: ______________________________________ BET surface acc. to DIN 66 131 m.sup.2 /g 110 ± 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 Loss at red heat (related to the substance dried for 2 hours at 105° C.) acc. to DIN 55 921 % 5.5 ± 1.5 pH value (in 5% aqueous dis- persion) acc. to DIN 53 200 7 ± 1 Conductivity (in 4% aqueous dispersion) μS <600 Tamped density of the unaerated substance acc. to DIN 53 194 g/l 50 ± 20 Water wettability <0.05 Carbon content % 2.5 ± 0.6 Water absorption at 30° C. & 30%RM % 1.2 ± 0.4 at 30° C. & 70%RM % 1.5 ± 0.5 DBP adsorption % 260 ± 30 ______________________________________ said hydrophobic silicic acid having been prepared by treating and agitating a precipitated silicic acid with a hydrophobic agent and grinding to form a finely divided product, said precipitated silicic acid having the following properties: ______________________________________ BET surface acc. to DIN 66 131 m.sup.2 /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 150° 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 dispersion) acc. to DIN 53 200 3.5-5.5 Conductivity (in 5% aqueous dispersion) μS <500 Tamped density of the unaerated substance acc. to DIN 53 194 g/l 60 ± 20 SO.sub.3 content (related to the substance dried for 2 hours at 105° C.) % <0.3 Na.sub.2 O content (related to the substance dried for 2 hours at 105° C.) % <0.3 ______________________________________

Claim 4

Hydrophobic silicic acid having the following properties: ______________________________________ BET surface acc. to DIN 66 131 m.sup.2 /g 110 ± 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 Loss at red heat (related to the substance dried for 2 hours at 105° C.) acc. to DIN 55 921 % 5.5 ± 1.5 pH value (in 5% aqueous dis- persion) acc. to DIN 53 200 7 ± 1 Conductivity (in 4% aqueous dispersion) μS <600 Tamped density of the unaerated substance acc. to DIN 53 194 g/l 50 ± 20 Water wettability <0.05 Carbon content % 2.5 ± 0.6 Water absorption at 30° C. & 30%RM % 1.2 ± 0.4 at 30° C. & 70%RM % 1.5 ± 0.5 DBP adsorption % 260 ± 30 ______________________________________ said hydrophobic silicic acid having been prepared by treating and agitating a precipitated silicic acid with a hydrophobic agent and grinding to form a finely divided product, said precipitated silicic acid having the following properties: ______________________________________ BET surface acc. to DIN 66 131 m.sup.2 /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 150° 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 dispersion) acc. to DIN 53 200 3.5-5.5 Conductivity (in 5% aqueous dispersion) μS <500 Tamped density of the unaerated substance acc. to DIN 53 194 g/l 60 ± 20 SO.sub.3 content (related to the substance dried for 2 hours at 105° C.) % <0.3 Na.sub.2 O content (related to the substance dried for 2 hours at 105° C.) % <0.3 ______________________________________

Claim 5

An elestomeric forming composition comprising precipitated silicic acid as defined in claim 1 as a reinforcing filler in a mass which may be hardened into an elastomer.

Claim 6

An elastomeric forming composition according to claim 3 wherein a hot vulcanizing diorganopolysiloxane elastomer is used as the elastomer.

Claim 7

An elastomeric forming composition according to claim 3 wherein an organopolysiloxane elastomer which may be hardened at room temperature is used as the elastomer.

Claim 8

An elastomeric forming composition according to claim 5 wherein a 2-component silicone molding material is used as the organopolysiloxane elastomer and which is hardenable at room temperature.

Claim 9

An elastomeric forming composition according to claim 5 wherein a 1-component sealing mass for joints is used as the organopolysiloxane elastomer and which is hardenable at room temperature.

Claim 10

A cured elastomer composition comprising a finely divided filler which is a precipitated silicic acid as defined in claim 1 homogeneously dispersed in the elastomeric binder.