Degussa Aktiengesellschaft

Deutsche Gold- Und Silber-scheideanstalt Vormals Roessler

Degussa - Huls Ag

Degussa Aktiengsellschaft

Heinz Esch

Robert Kuhlmann

Ralf Rausch

Gunter Turk

Peter Nauroth

Rudolf Bode

Arthur Reisert

Karl Meier

Udo Goerl

Mustafa Siray

Udo Gorl

Karin Otto

Udo Görl

Harald Buhler

Andrea Hunsche

Wolfgang Leonhardt

Werner Nagel

Matthias Neum&uuml;ller

Mattias Neumueller

Walter Meon

Klaus-Peter Thomas

Guenter Tuerk

Buhler, Harald

Marian Chjonowski

Rubber compositions comprising a precipitated silica with the following physico-chemical properties: 

Precipitated silicas

A precipitated silica with the following physicochemical properties: is produced by reacting alkali silicate with mineral acids at temperatures of 60&#xb0; C. to 95&#xb0; C. while maintaining a pH of 7.5 to 10.5 and continuously stirring, continuing the reaction to a solids concentration in the precipitation suspension of 90 g/l to 120 g/l, adjusting the pH value to a value of less than or equal to 5, filtering out, washing, drying and optionally grinding or granulating the precipitated silica. The precipitated silica is used as a filler in vulcanizable rubber compounds and vulcanizates.

A precipitated silica which contains an active substance with a characteristic, delayed release of active substance is prepared by adding the active substance during preparation of the precipitated silica. The precipitated silica containing the active substance may be added to oral hygiene agents such as toothpastes, topical fluoride preparations, dental materials or medicinal chewing gums.

Precipitated silicas which contain an active substance

A precipitated silica with the following physicochemical properties:

Precipitated silica with a sodium sulphate content of 4 to 18 wt. %, particularly with the physical-chemical data:

Precipitated silica

Precipitated silicas, characterized in that they have a CTAB surface area (in accordance with ASTM D 3765-92) of 200 to 400 m.sup.2 /g, a DBP index (in accordance with ASTM D 2414) between 230 and 380 ml/100 g as powder and 180-250 g/100 g as granulate, a silanol group density (V.sub.2 -NaOH consumption) of 20 to 30 ml and the following macropore size distribution which is typical of the surface area range involved, determined by means of Hg porosimetry (DIN 66 133) for specific pore size intervals (incremental mode of application):

Precipitated silicas, a process for their preparation and their use in

Precipitated silica which has a BET surface area of 10-130 m.sup.2 /g, a CTAB surface area of 10-70 m.sup.2 /g , an average particle diameter of 5-20 .mu.m, a Cu abrasion value in a 10% glycerol dispersion of 4-50 mg and thickening behavior in a CMC solution (20% dispersion) of 300-3500 mPa.multidot.s, is produced by simultaneously adding alkali silicate (weight modulus SiO.sub.2 :alkali oxide=2.5-3.9:1) and a mineral acid to an initial amount of water which has been adjusted to a pH value of 7.0 to 9.9 or 10.0 to 10.7 by the addition of water glass, holding the pH value constant between 7.0 and 9.9 or 10.0 to 10.7 during addition, wherein the initial precipitation temperature is 50.degree.-90.degree. C. and an increase in viscosity occurs after at most 25% of the duration of precipitation, adjusting the pH value to .ltoreq.6, preferably 3.5, once a silica content of greater than 120 g/l or greater than 150 g/l, preferably .gtoreq.160 g/l to 240 g/l, has been reached, separating the solid by filtration, washing, drying and grinding it. The precipitated silica may be used as an abrasive and/or thickening component in toothpastes.

Process for the production of precipitated silica

A precipitated silica paste is produced by dispersing precipitated silica in silicon oil. During the hydrophobing of precipitated silicas, the precipitated silica paste is added as a hydrophobing agent in the suspension phase. The product is spray-dried, tempered and ground.

Precipitated silica paste

There are disclosed precipitated silicas which are characterized by the following physical-chemical data:

Precipitated silicas having high structure and process for their

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.

Precipitated silicic acid, method and compositions containing same

Hydrophobic precipitated silicic acid is disclosed and its use as a reinforcing filler in plastic masses which are hardenable to form elastomers.

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Bonn, Germany

Heinz Esch