Highly dispersible precipitated silica
View Patent ↗The present invention relates to a highly disperse precipitated silica which has a high surface area, to a process for preparing it, and to its use as a tire filler for commercial vehicles, motorbikes, and high-speed vehicles.
1. A precipitated silica, wherein said silica has the following properties:
BET surface area
190-302 m 2 /g,
CTAB surface area
≧170 m 2 /g,
DBP number
200-300 g/(100 g), and
Sears number V 2
10-20 ml/(5 g).
2. The precipitated silica as claimed in claim 1 , wherein the CTAB surface area is not more than 300 m 2 /g.
3. The precipitated silica as claimed in claim 1 , having a WK coefficient of ≦3.4 (ratio of the peak height of the particles which cannot be broken down by ultrasound in the size range 1.0-100 μm, to the peak height of the broken-down particles in the size range <1.0 μm).
4. The precipitated silica as claimed in claim 1 , wherein the surfaces of said silica have been modified with organosilanes of the formulae I to III:
[SiR 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),
wherein
B is —SCN, —SH, —Cl, —NH 2 , —OC(O)CHCH 2 , —OC(O)C(CH 3 )CH 2 (if q=1) or —Sw— (if q=2), B being bonded chemically to Alk,
R and R 1 are aliphatic, olefinic, aromatic or arylaromatic radicals having 2-30 carbon atoms, which may optionally 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, acrylate, meth-acrylate, organosilane radicals, and wherein R and R 1 may have an identical or different definition or substitution,
n is 0, 1 or 2,
Alk is a divalent 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, which may 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, organosilane radicals,
p is 0 or 1 with the proviso that p and n are not simultaneously 0,
q is 1 or2,
w 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, and
Alkenyl is a monovalent unbranched or branched unsaturated hydrocarbon radical having from 2 to 20 carbon atoms.
5. A process for preparing a precipitated silica having the following properties:
BET surface area
190-302 m 2 /g,
CTAB surface area
≧170 m 2 /g,
DBP number
200-300 g/(100 g),
Sears number V 2
10-20 ml/(5 g);
wherein said process comprises:
a) introducing, as an initial charge, an aqueous solution of an alkali metal silicate or alkaline earth metal silicate and/or an organic and/or inorganic base with pH 7.0-8.5,
b) adding, simultaneously by metered addition, waterglass and an acidifier into the initial charge, with stirring at 55-95° C. for 10-120 minutes,
e) acidifying the mixture with an acidifier to a pH of approximately 3.5, and
f) filtering and drying the acidified mixture.
6. The process as claimed in claim 5 , further comprising carrying out between steps b) and e) the following steps:
c) stopping the metered addition for 30-90 minutes, during which the temperature is maintained, and
d) adding, simultaneously by metered addition, waterglass and an acidifier at the same temperature with stirring for 20-120 minutes.
7. The process as claimed in claim 6 , wherein the acidifier and/or the waterglass in steps b) and d), each have the same concentration or rate of addition.
8. The process as claimed in claim 6 , wherein the acidifier and/or the waterglass in steps b) and d), each have a different concentration or rate of addition.
9. The process as claimed in claim 8 , wherein the acidifier and/or the waterglass have the same concentration in steps b) and d), and their rate of addition in step d) is 125-140% of the rate of addition in step b).
10. The process as claimed in claim 5 , wherein drying is carried out using a pneumatic conveying drier, spray drier, rack drier, belt drier, rotary tube drier, flash drier, spin-flash drier or nozzle tower.
11. The process as claimed in claim 5 , wherein drying is followed by granulation with a roll compactor.
12. The process as claimed in claim 5 , wherein during steps b) and/or d), an organic or inorganic salt is added.
13. The process as claimed in claim 5 , wherein the precipitated silica is granulated or ungranulated, and wherein the granulated or ungranulated precipitated silica is modified with organosilanes in mixtures from 0.5 to 50 parts per 100 parts of precipitated silica, and the reaction between precipitated silica and organosilane is carried out during the preparation of the mixture (in situ), or outside by spray application and subsequent thermal conditioning of the mixture, or by mixing the organosilane and the silica suspension with subsequent drying and thermal conditioning.
14. An elastomeric blend, a vulcanized rubber blend or a vulcanizate, each comprising the precipitated silica of claim 1 , and one or more polymeric resins.
15. A tire comprising the precipitated silica as claimed in claim 1 , and one or more rubbers or elastomers.
16. The tire as claimed in claim 15 , wherein said tire is a commercial vehicle tire.
17. The tire as claimed in claim 15 , wherein said tire is a motorbike tire.
18. The tire as claimed in claim 15 , wherein said tire is a high-speed vehicle tire.
19. A vehicle, comprising the tire of claim 15 , and a body frame.
20. An article, comprising the elastomeric blend, the vulcanized rubber blend or the vulcanizate of claim 14 , and one or more additives.
21. The precipitated silica as claimed in claim 1 , wherein the CTAB surface area is 170-220 m 2 /g.
22. The precipitated silica as claimed in claim 1 , wherein the CTAB surface area is 245-300 m 2 /g.
23. The precipitated silica as claimed in claim 1 , wherein the BET surface area is 257-300 m 2 /g.
24. The precipitated silica as claimed in claim 1 , wherein the BET surface area is 190-230 m 2 /g.
25. The precipitated silica as claimed in claim 1 , wherein the DBP number is 207-276 g/(100 g).
26. The precipitated silica as claimed in claim 1 , wherein the Sears number V 2 is 10-16 ml/ (5 g).
27. The precipitated silica as claimed in claim 3 , wherein the WK coefficient is ≦3.0.
28. The precipitated silica as claimed in claim 3 , wherein the WK coefficient is ≦2.5.