Diene rubber composition for tire comprising a specific silica as reinforcing filler
View Patent ↗Diene rubber compositions are described containing a diene elastomer, a reinforcing inorganic filler, and a coupling agent wherein the inorganic filler includes a silica having the following characteristics: (a) a BET specific surface area between 45 and 400 m 2 /g; (b) a CTAB specific surface area between 40 and 380 m 2 /g; (c) an average particle size (by mass), d w , of 20 to 300 nm; and at least one of the following characteristics, preferably two and more preferably all three: (d) a particle size distribution such that dw≧/CTAB)−30; (e) a porosity which meets the criterion L/FI≧−0.0025 CTAB+0.85; (f) an amount of silanols per unit of surface area, N SiOH/nm 2 ; N SiOH/nm 2 ≦−0.027 CTAB+10.5. These diene rubber compositions can be used for the manufacture of tires or of semi-finished products intended for tires.
1. A tire comprising a rubber composition comprising at least a diene elastomer, a reinforcing inorganic filler, and a coupling agent providing the bond between the reinforcing filler and the elastomer, wherein said inorganic filler comprises at least one silica having all the following characteristics:
a) a BET specific surface area of between 45 and 400 m 2 /g;
b) a CTAB specific surface area of between 40 and 380 m 2 /g;
c) an average particle size (by mass), d w , of 20 to 300 nm;
d) a particle size distribution such that
d w ≧(16,500/CTAB)−30;
e) a porosity which meets the criterion
L/FI≧−0.0025 CTAB+0.85;
f) an amount of silanols per unit of surface area, N SiOH/nm 2 ,
N SiOH/nm 2 ≦−0.027CTAB+10.5.
2. The tire according to claim 1 , said silica having a BET specific surface area of between 80 and 300 m 2 /g and a CTAB specific surface area of between 70 and 280 m 2 /g.
3. The tire according to claim 2 , said silica having a BET specific surface area of between 130 and 300 m 2 /g and a CTAB specific surface area of between 120 and 280 m 2 /g.
4. The tire according to claim 1 , said silica having BET and CTAB specific surface areas, S BET and S CTAB , which satisfy the relationship (S BET -S CTAB )≧5 m 2 /g.
5. The tire according to claim 4 , said silica having BET and CTAB specific surface areas which satisfy the relationship (S BET -S CTAB )<50 m 2 /g.
6. The tire according to claim 1 , said silica having a disagglomeration rate, α, measured by means of an ultrasound disagglomeration test in pulse mode (1 s ON, 1 s OFF), at 100% power of a 600 W ultrasound probe, of at least 0.0035 μm −1 .mn −1 .
7. The tire according to claim 1 , wherein said composition further comprises carbon black in an amount of between 2 and 20 phr.
8. The tire according to claim 7 , wherein the amount of carbon black is in a range of from 5 to 15 phr.
9. The tire according to claim 1 , wherein said coupling agent is selected from the group consisting of the polysulphurized alkoxysilanes of the formula (I):
wherein:
R 1 , which may be identical or different, each represents a monovalent hydrocarbon group selected from the group consisting of straight-chain and branched alkyls having from 1 to 4 carbon atoms, and straight-chain and branched alkoxyalkyls having from 2 to 8 carbon atoms;
R 2 and R 3 , which may be identical or different, each represents a monovalent hydrocarbon group selected from the group consisting of straight-chain and branched alkyls having from 1 to 6 carbon atoms, and phenyl; and
x is an integer or fraction of between 3 and 5.
10. The tire according to claim 9 , wherein said coupling agent is selected from the group consisting of the polysulphurized alkoxysilanes of the formulae (II), (III) and (IV):
11. The tire according to claim 10 , wherein said coupling agent is monoethoxydimethylsilylpropyl tetrasulphide of formula [(C 2 H 5 O)(CH 3 ) 2 Si(CH 2 ) 3 S 2 ] 2 .
12. The tire according to claim 1 , wherein said rubber composition is present in the tread of the tire.