Aluminum-containing precipitated silicic acid having an adjustable BET/CTAB ratio

1. A precipitated silica comprising

a BET surface area of 150-400 m 2 /g,

a CTAB surface area of 145-350 m 2 /g,

an Al 2 O 3 content of 0.2-5% by weight and

a modified Sears number V 2 of 5-35 ml/(5 g), and

a BET/CTAB surface ratio of from 1.33 to 2.43.

2. The precipitated silica of claim 1 , wherein the precipitated silica has a DBP absorption of from 180 to 320 g/100 g.

3. The precipitated silica of claim 1 , wherein the precipitated silica has a wk coefficient ≦3.4.

4. The precipitated silica of claim 1 , wherein the precipitated silica surface has been modified with an organosilance of the formulae

[R 1 n (RO) r Si(Alk) m (Ar) p ] q [B]  (I),

R 1 n (RO) 3-n Si(Alkyl)  (II)

or

R 1 n (RO) 3-n SI (Alkenyl)  (III),

in which

B is —SCN, —SH, —SC(O)CH 3 , —SC(O)(CH 2 ) 6 CH 3 , Cl, —NH 2 , —OC(O)CHCH 2 , —OC(O)C(CH 3 )CH 2 (if q=1), or —S x — (if q=2),

R and R 1 are each an aliphatic, olefinic, aromatic or arylaromatic radical having 2 to 30 carbon atoms, and optionally substituted with the following groups; hydroxyl, amino, alkoxide, cyanide, thiocyanide, halogen, sulfonic acid, sulfonic ester, thiol, benzoic acid, benzoic ester, carboxylic acid, carboxylic ester, acrylate, methacrylate or organosilane radical, it being possible for R and R 1 to have an identical or different definition or substitution,

n is 0, 1 or 2,

Alk is a divalent unbranched or branched hydrocarbon radical having 1 to 6 carbon atoms, m is 0 or 1,

Ar is an aryl radical having 6 to 12 carbon atoms, which can be substituted by the following groups: hydroxyl, amino, alkoxide, cyanide, thiocyanide, halogen, sulfonic acid, sulfonic ester, thiol, benzoic acid, benzoic ester, carboxylic acid, carboxylic ester or organosilane radical,

p is 0 or 1, with the proviso that p and n are not simultaneously 0,

x is a number from 2 to 8,

r is 1, 2 or 3, with the proviso that r+n+m+p=4,

Alkyl is a monovalent unbranched or branched unsaturated hydrocarbon radical having 1 to 20 carbon atoms, Alkenyl is a monovalent unbranched or branched unsaturated hydrocarbon radical having 2 to 20 carbon atoms.

5. The precipitated silica of claim 4 , wherein Ar has 6 carbon atoms, Alkyl has 2 to 8 carbon atoms, and Alkenyl has 2 to 8 carbon atoms.

6. The precipitated silica of claim 1 , wherein the BET surface area is 195-400 m 2 /g.

7. A process for preparing the precipitated silica of claim 1

a) charging an aqueous waterglass solution into a reactor,

b) metering waterglass and sulfuric acid as components into the reactor simultaneously into this initial charge at from 55 to 95° C. for from 30 to 100 minutes with stirring forming a mixture,

c) acidifying the mixture with the sulfuric acid to a pH of about 5 to form the precipitated silica, and

d) filtering and drying the precipitated silica,

with the proviso that aluminum compounds are added in steps b) and/or c).

8. The process of claim 7 , wherein the components supplied in steps b) and c) each have an identical or different concentration.

9. The process of claim 7 , wherein the components supplied in steps b) and c) each have an identical feed rate.

10. The process of claim 7 , wherein the components supplied in steps b) and c) each have a different feed rate.

11. The process of claim 10 , wherein with an identical concentration of the components in steps b) and c) the feed rate in step c) is from 110 to 200% of the feed rate in step b).

12. The process of claim 10 , wherein with an identical concentration of the components in steps b) and c) the feed rate in step c) is from 50 to 100% of the feed rate in step b).

13. The process of claim 7 , wherein the drying is carried out by spin-flash, nozzle tower or spray drying and/or granulation with/without a roll compactor.

14. The process of claim 7 , wherein the precipitated silica is modified with organosilanes of the formula I to III mixtures of from 0.5 to 50 parts, based on 100 parts of precipitated silica, in particular from 1 to 15 parts, based on 100 parts of precipitated silica, the reaction between precipitated silica and organosilane being carried out during the preparation of the mixture (in situ) or externally by spray application and subsequent thermal conditioning of the mixture or by mixing of the silane and the silica suspension with subsequent drying and thermal conditioning.

15. A vulcanizable rubber mixture or vulcanizate comprising the precipitated silica of claim 1 .

16. A tire comprising the precipitated silica of claim 1 .

17. A vulcanizable rubber mixture or vulcanizate comprising the precipitated silica prepared according to claim 7 .

18. A tire comprising the precipitated silica prepared according to claim 7 .

19. A battery separator, an anti-blocking agent, a flatting agent in a paint, a paper coating, a defoamer, a gasket, a keypad, a conveyor belt or a window seal comprising the precipitated silica as claimed in claim 1 .