Rubber composition for magnesium hydroxide wafer-reinforced tire
The invention relates to a rubber composition having improved vulcanization kinetics, which can be used in particular for manufacturing tires or semi-finished products for tires, based on at least one diene elastomer, a reinforcing filler and a coupling agent providing the bond between filler and elastomer, characterized in that said reinforcing filler comprises synthetic magnesium hydroxide Mg(OH) 2 wafers, covered with silica. The invention also relates to the use of such a composition for manufacturing rubber articles, in particular tires or semi-finished products made of rubber intended for these tires, especially treads. The invention also relates, per se, to this synthetic magnesium hydroxide in the form of silica-covered wafers, and also to its use as a reinforcing filler, especially in a diene elastomer matrix.
1. A rubber composition based on at least one diene elastomer, a reinforcing filler and a coupling agent, wherein said reinforcing filler comprises synthetic magnesium hydroxide Mg(OH) 2 covered with silica, wherein the synthetic magnesium hydroxide Mg(OH) 2 has a specific surface area, measured by a BET method, between 60 and 180 m 2 /g, and wherein the synthetic magnesium hydroxide Mg(OH) 2 is composed of aggregates agglomerated together, the aggregates include magnesium hydroxide Mg(OH) 2 particles which are anisometric and in the form of wafers, and the magnesium hydroxide Mg(OH) 2 particles have an aspect ratio (A 2 =L 2 /T 2 ) greater than 1.5, L 2 and T 2 respectively representing the number-average length and thickness of the particles.
2. The composition according to claim 1 , the diene elastomer being selected from the group consisting of polybutadienes, synthetic polyisoprenes, natural rubber, butadiene/styrene copolymers, butadiene/isoprene copolymers, isoprene/styrene copolymers, butadiene/styrene/isoprene copolymers and blends of these elastomers.
3. The composition according to claim 1 , the coupling agent being a silane or a polysiloxane that is at least bifunctional.
4. The composition according to claim 1 , the amount by weight of silica at the surface of the magnesium hydroxide wafers representing between 5% and 50% of the total weight of the wafers.
5. The composition according to claim 1 , the amount of magnesium hydroxide in said composition being greater than 50 phe.
6. The composition according to claim 1 , said aggregates being in the form of wafers having an aspect ratio (A 1 =L 1 /T 1 ) greater than 2.0, L 1 and T 1 respectively representing the number-average length and thickness of said aggregates.
7. The composition according to claim 6 , the aspect ratio (A 1 ) of the aggregates being between 3 and 10.
8. The composition according to claim 1 , the aspect ratio (A 2 ) of the primary particles being between 2 and 10.
9. The composition according to claim 1 , L 2 being between 10 and 400 nm and T 2 being between 5 and 30 nm.
10. The composition according to claim 9 , L 2 being in the range of 20 to 150 nm and T 2 being in the range of 10 to 25 nm.
11. A process for obtaining a diene rubber composition having improved vulcanization kinetics, into which at least one diene elastomer, at least one reinforcing filler and a coupling agent are incorporated, wherein said filler comprises synthetic magnesium hydroxide Mg(OH) 2 covered with silica, wherein the synthetic magnesium hydroxide Mg(OH) 2 has a specific surface area, measured by a BET method, between 60 and 180 m 2 /g, wherein the synthetic magnesium hydroxide Mg(OH) 2 is composed of aggregates agglomerated together, the aggregates include magnesium hydroxide Mg(OH) 2 particles which are anisometric and in the form of wafers, the magnesium hydroxide Mg(OH) 2 particles have an aspect ratio (A 2 =L 2 /T 2 ) of greater than 1.5, L 2 and T 2 respectively representing the number-average length and thickness of the particles, and wherein the entire mixture is kneaded thermomechanically, in one or more steps, until a maximum temperature between 110° C. and 190° C. is attained.
12. A finished article or semi-finished product made of the rubber composition according to claim 1 .
13. A rubber article comprising the composition according to claim 1 .
14. A tire comprising the rubber composition according to claim 1 .
15. A tire tread comprising the rubber composition according to claim 1 .
16. Synthetic magnesium hydroxide Mg(OH) 2 covered with silica, wherein the synthetic magnesium hydroxide Mg(OH) 2 has a specific surface area, measured by a BET method, between 60 and 180 m 2 /g, and wherein the synthetic magnesium hydroxide Mg(OH) 2 is composed of particles which are anisometric and in the form of wafers, and the magnesium hydroxide Mg(OH) 2 particles have an aspect ratio (A 2 =L 2 /T 2 ) of greater than 1.5, L 2 and T 2 respectively representing the number-average length and thickness of the particles.
17. The synthetic magnesium hydroxide Mg(OH) 2 according to claim 16 , the amount by weight of silica at the surface of the magnesium hydroxide wafers representing between 5% and 50% of the total weight of the wafers.
18. The synthetic magnesium hydroxide Mg(OH) 2 according to claim 17 , the amount by weight of silica at the surface of the magnesium hydroxide wafers representing between 10% and 40% of the total weight of the wafers.
19. The synthetic magnesium hydroxide Mg(OH) 2 according to claim 16 , the particles forming aggregates in the form of wafers which have an aspect ratio (A 1 =L 1 /T 1 ) greater than 2.0, L 1 and T 1 respectively representing the number-average length and thickness of said aggregates.
20. The synthetic magnesium hydroxide Mg(OH) 2 according to claim 19 , the aspect ratio (A 1 ) of the aggregates being between 3 and 10.
21. The synthetic magnesium hydroxide Mg(OH) 2 according to claim 16 , the aspect ratio (A 2 ) of the particles being between 2 and 10.
22. The synthetic magnesium hydroxide Mg(OH) 2 according to claim 16 , L 2 being between 10 and 400 nm and T 2 being between 5 and 30 nm.
23. The synthetic magnesium hydroxide Mg(OH) 2 according to claim 22 , L 2 being in a range of 20 to 150 nm and T 2 being in a range of 10 to 25 nm.
24. A reinforcing filler comprising the synthetic magnesium hydroxide Mg(OH)2 covered with silica, according to claim 16 .
25. The composition according to claim 4 , the amount by weight of silica representing between 10% and 40% of the total weight of the waters.
26. The composition according to claim 6 , the aspect ratio of the aggregates being greater than 3.0.
27. The composition according to claim 1 , the aspect ratio (A 2 ) of the particles being greater than 2.0.
28. The synthetic magnesium hydroxide Mg(OH) 2 according to claim 19 , the aspect ratio (A 1 ) of the aggregates being greater than 3.0.
29. The synthetic magnesium hydroxide Mg(OH) 2 according to claim 16 , the aspect ratio (A 2 ) of the particles being greater than 2.0.