Specially precipitated silicic acids for rubber applications

1. A precipitated silica which has the following physical and chemical properties:

CTAB surface area

100-200

m 2 /g,

BET surface area

80-110

m 2 /g,

BET/CTAB ratio

0.9 to 1.03,

DBP value

210-280

g/(100 g),

Sears value V2

21-30

ml/(5 g),

Moisture level

4-8%,

and

Ratio of Sears value V 2 to

0.150 to 0.370

ml/(5 m 2 )

BET surface area.

2. The precipitated silica as claimed in claim 1 , wherein the Sears value V 2 is from 21 to 28 ml/(5 g).

3. The precipitated silica as claimed in claim 1 , wherein the CTAB surface area is from 100 to 160 m 2 /g.

4. The precipitated silica as claimed in claim 1 , wherein the DBP value is from 250 to 280 g/(100 g).

5. The precipitated silica as claimed in claim 1 , wherein the ratio of Sears value V 2 to the BET surface area is from 0.180 to 0.370 ml/(5 m 2 ).

6. The precipitated silica claimed in claim 1 , wherein the surface of the precipitated silica has been modified with organosilanes of the formulae I to III

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

SiR 1 n (RO) 3-n (Alkyl)  (II),

or

SiR 1 n (RO) 3-n (Alkenyl)  (III),

where

B is —SCN, —SH, —Cl, —NH 2 , —OC(O)CHCH 2 , —OC(O)C(CH 3 )CH 2 (if q=1), or —S w — (if q=2), B being chemically bonded to Alk,

R and R 1 are an aliphatic, olefinic, aromatic, or arylaromatic radical having 2-30 carbon atoms, optionally with substitution by the following groups: the hydroxyl, amino, alcoholate, cyanide, thiocyanide, halo, sulfonic acid, sulfonic ester, thiol, benzoic acid, benzoic ester, carboxylic acid, carboxylic ester, acrylate, methacrylate, or organosilane radical, where the meaning or substitution of R and R 1 may be identical or different,

n is 0, 1, or 2,

Alk is a bivalent unbranched or branched hydrocarbon radical having from 1 to 6 carbon atoms,

m is 0 or 1,

Ar is an aryl radical having from 6 to 12 carbon atoms, preferably 6 carbon atoms, which may have substitution by the following groups: the hydroxyl, amino, alcoholate, cyanide, thiocyanide, halo, sulfonic acid, sulfonic ester, thiol, benzoic acid, benzoic ester, carboxylic acid, carboxylic ester, acrylate, methacrylate or organosilane radical,

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

q is 1 or 2,

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 saturated hydrocarbon radical having from 1 to 20 carbon atoms, preferably from 2 to 8 carbon atoms,

Alkenyl is a monovalent unbranched or branched unsaturated hydrocarbon radical having from 2 to 20 carbon atoms, preferably from 2 to 8 carbon atoms.

7. A process for preparing the precipitated silica as claimed in claim 6 , wherein the precipitated silicas are modified with organosilanes in 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, where the reaction between precipitated silica and organosilane is carried out during the preparation of the mixture (in situ) or externally via spray application and subsequent heat-conditioning of the mixture, via mixing of the organosilane and the silica suspension with subsequent drying and heat-conditioning.

8. The precipitated silica as claimed in claim 1 , wherein the surface of the precipitated silica has been modified with organosilicon compounds whose composition is

SiR 2 4-n X n (where n=1, 2, 3, 4),

[SiR 2 x X y O] z (where 0≦x≦2; 0≦y≦2; 3≦z≦10, where x+y=2),

[SiR 2 x X y N] z (where 0≦x≦2; 0≦y≦2; 3≦z≦10, where x+y=2),

SiR 2 n X m OSiR 2 o X p (where 0≦n≦3; 0≦m≦3; 0≦o≦3; 0≦p≦3, where n+m=3, o+p=3),

SiR 2 n X m NSiR 2 o X p (where 0≦n≦3; 0≦m≦3; 0≦o≦3; 0≦p≦3, where n+m=3, o+p=3), and/or

SiR 2 n X m [SiR 2 x X y O] z SiR 2 o X p (where 0≦n≦3; 0≦m≦3; 0≦x≦2; 0≦y≦2;

0≦o≦3; 0≦p≦3; 1≦z≦10000, where n+m=3, x+y=2, o+p=3)

where

R 2 is alkyl and/or aryl radicals, substituted and/or unsubstituted, having from 1 to 20 carbon atoms, and/or is alkoxy, and/or alkenyl, and/or alkynyl groups, and/or is sulfur-containing groups,

X is a silanol, amino, thiol, halogen, alkoxy, alkenyl and/or hydrogen radical.

9. A process for preparing the precipitated silica as claimed in claim 8 , wherein the precipitated silicas are modified with organosilanes in 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, where the reaction between precipitated silica and organosilane is carried out during the preparation of the mixture (in situ) or externally via spray application and subsequent heat-conditioning of the mixture, via mixing of the organosilane and the silica suspension with subsequent drying and heat-conditioning.

10. A method for producing the article as claimed in claim 9 , comprising: adding the precipitated silica to the article during the manufacture of the article.

11. A process for preparing the precipitated silica as claimed in claim 1 , wherein

in succession

a) an aqueous solution of an alkali metal silicate or alkaline earth metal silicate and/or of an organic and/or inorganic base with pH from 7 to 14 is taken as initial charge,

b) water glass and an acidifier are metered simultaneously into this initial charge at from 55 to 95° C., with stirring, for from 10 to 120 minutes,

g) stirring of the resultant suspension is continued at from 80 to 98° C., for from 1 to 120 minutes,

h) an acidifier is used to acidify to pH of from 2.5 to 5, and

i) the material is filtered and dried.

12. The process as claimed in claim 11 , further comprising after b):

c) stopping the feed for from 30 to 90 minutes while maintaining the temperature,

and

d) then, where appropriate, simultaneously feeding water glass and an acidifier at the same temperature, with stirring, for from 20 to 120 minutes, preferably from 20 to 80 minutes are carried out once or twice.

13. The process as claimed in claim 11 , further comprising, following b) or d), e) adjusting the pH to from 3 to 11 by adding an acidifier.

14. The process as claimed in claim 13 , wherein, the pH is adjusted to from 7 to 10 by adding acid.

15. The process as claimed in claim 13 , further comprising: f) increasing the pH to from 8 to 14 by adding a basic compound.

16. The process as claimed in claim 15 , wherein the basic compound is at least one selected from the group consisting of an alkali metal silicate, an alkaline earth metal silicate, an alkali metal hydroxide and an alkaline earth metal hydroxide.

17. The process as claimed in claim 11 , further comprising adding an organic or inorganic salt in any one of a) to h).

18. The process as claimed in claim 11 , wherein drying is conducted in a pneumatic drier, spray drier, disk drier, belt drier, rotating-tube drier, flash drier, spin flash drier, or spray tower.

19. The process as claimed in claim 11 ,

further comprising pelletizing the dried precipitated silica in a roller compactor.

20. A vulcanizable rubber mixture or a vulcanizate comprising the precipitated silica as claimed in claim 1 .

21. The vulcanizable rubber mixture or vulcanizate as claimed in claim 20 , wherein the surface of the precipitated silica has been modified with organosilanes of the formulae I to III

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

SiR 1 n (RO) 3-n (Alkyl)  (II),

or

SiR 1 n (RO) 3-n (Alkenyl)  (III),

where

B is —SCN, —SH, —Cl, —NH 2 , —OC(O)CHCH 2 , —OC(O)C(CH 3 )CH 2 (if q=1), or —S w — (if q=2), B being chemically bonded to Alk,

R and R 1 are an aliphatic, olefinic, aromatic, or arylaromatic radical having 2-30 carbon atoms, optionally with substitution by the following groups: the hydroxyl, amino, alcoholate, cyanide, thiocyanide, halo, sulfonic acid, sulfonic ester, thiol, benzoic acid, benzoic ester, carboxylic acid, carboxylic ester, acrylate, methacrylate, or organosilane radical, where the meaning or substitution of R and R 1 may be identical or different,

n is 0, 1, or 2,

Alk is a bivalent unbranched or branched hydrocarbon radical having from 1 to 6 carbon atoms,

m is 0 or 1,

Ar is an aryl radical having from 6 to 12 carbon atoms, preferably 6 carbon atoms, which may have substitution by the following groups: the hydroxyl, amino, alcoholate, cyanide, thiocyanide, halo, sulfonic acid, sulfonic ester, thiol, benzoic acid, benzoic ester, carboxylic acid, carboxylic ester, acrylate, methacrylate or organosilane radical,

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

q is 1 or 2,

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 saturated hydrocarbon radical having from 1 to 20 carbon atoms, preferably from 2 to 8 carbon atoms,

Alkenyl is a monovalent unbranched or branched unsaturated hydrocarbon radical having from 2 to 20 carbon atoms, preferably from 2 to 8 carbon atoms.

22. The vulcanizable rubber mixture or vulcanizate as claimed in claim 20 , wherein the surface of the precipitated silica has been modified with organosilicon compounds whose composition is

SiR 2 4-n X n (where n=1, 2, 3, 4),

[SiR 2 x X y O] z (where 0≦x≦2; 0≦y≦2; 3≦z≦10, where x+y=2),

[SiR 2 x X y N] z (where 0≦x≦2; 0≦y≦2; 3≦z≦10, where x+y=2),

SiR 2 n X m OSiR 2 o X p (where 0≦n≦3; 0≦m≦3; 0≦o≦3; 0≦p≦3, where n+m=3, o+p=3),

SiR 2 n X m NSiR 2 o X p (where 0≦n≦3; 0≦m≦3; 0≦o≦3; 0≦p≦3, where n+m=3, o+p=3), and/or

SiR 2 n X m [SiR 2 x X y O] z SiR 2 o X p (where 0≦n≦3; 0≦m≦3; 0≦x≦2; 0≦y≦2;

0≦o≦3; 0≦p≦3; 1≦z≦10000, where n+m=3, x+y=2, o+p=3)

where

R 2 is alkyl and/or aryl radicals, substituted and/or unsubstituted, having from 1 to 20 carbon atoms, and/or is alkoxy, and/or alkenyl, and/or alkynyl groups, and/or is sulfur-containing groups,

X is a silanol, amino, thiol, halogen, alkoxy, alkenyl and/or hydrogen radical.

23. An article, comprising:

the precipitated silica as claimed in claim 1 ,

wherein said article is an elastomer mixture, a vulcanizable rubber mixture, a pneumatic tire, a tire tread, cable sheathing, a hose, a drive belt, a conveyor belt, a V-belt, a roller covering, a tire, a shoe sole, a gasket or a damping element.

24. A composition comprising the precipitated silica as claimed in claim 1 , wherein the composition is a battery separator, an antiblocking agent, a matting agent in inks and paints, a carrier for agricultural products and feeds, a coating, a printing ink, a fire extinguisher power, a plastic, a non-impact printing product, a paper pulp product or a personal care product.

25. A method for producing the composition as claimed in claim 24 , comprising adding the precipitated silica to the composition during the manufacture of the composition.

26. A precipitated silica which has the following physical and chemical properties:

CTAB surface area

100-160

m 2 /g,

BET/CTAB ratio

0.9-1.03,

BET surface area

80-110

m 2 /g,

DBP value

210-280

g/(100 g),

Sears value V2

21-30

ml/(5 g),

Moisture level

4-8%

Ratio of Sears value V 2 to

0.180 to 0.370

ml/(5 m 2 ),

BET surface area and

Primary particle diameter

10 to 50

nm

as determined by transmission electron spectroscopy (TEM) image evaluation.

27. A vulcanizable rubber mixture or a vulcanizate comprising the precipitated silica as claimed in claim 26 .

28. The precipitated silica as claimed in claim 26 , wherein said Sears value V2 is 25-28 ml/(5 g).

29. The vulcanizable rubber mixture or the vulcanizate as claimed in claim 27 , wherein the Sears value V2 of the precipitated silica is 25-28 ml/(5 g).

30. The precipitated silica as claimed in claim 26 , wherein the precipitated silica is in a form selected from the group consisting of a powder with an average diameter above 15 μm, round particles with an average diameter above 80 μm (microbeads), and pellets with an average diameter ≧1 mm.