Rubber composition and tire

1. A rubber composition comprising:

silica and

a rubber component that contains a modified butadiene rubber having a vinyl content of 35% by weight or less and having, in a main chain thereof, a constitutional unit derived from a nitrogen-containing compound represented by the formula:

wherein R 1 and R 2 are each hydrogen, the formula:

or the formula:

provided that at least one of R 1 and R 2 is not hydrogen,

R 3 represents hydrogen or a C 1-4 hydrocarbon group,

X represents a saturated ring-forming part consisting of (CR 8 R 9 ) l , (CR 10 R 11 ) m —NR 12 —(CR 13 R 14 ) n , (CR 10 R 11 ) m —O—(CR 13 R 14 ) n , or (CR 10 R 11 ) m —S—(CR 13 R 14 ) n ,

X may be substituted with the formula:

or the formula:

Z represents a saturated ring-forming part consisting of (CR 8 R 9 ) l , (CR 10 R 11 ) m —NR 12 —(CR 13 R 14 ) n , (CR 10 R 11 ) m —O—(CR 13 R 14 ) n , or (CR 10 R 11 ) m —S—(CR 13 R 14 ) n ,

R 4 to R 7 each represent hydrogen, a C 1-30 aliphatic hydrocarbon group, a C 3-30 alicyclic hydrocarbon group, a C 5-30 aromatic hydrocarbon group, or a heterocyclic group containing 3 to 30 annular atoms, and are the same as or different from each other,

R 0 , and R 8 to R 14 each represent hydrogen, a C 1-30 aliphatic hydrocarbon group, a C 3-30 alicyclic hydrocarbon group, or a C 5-30 aromatic hydrocarbon group, and are the same as or different from each other, and

l represents an integer of 3 to 10, and m and n each represent an integer of 1 to 9,

wherein the modified butadiene rubber consists essentially of constitutional units derived from butadiene and the constitutional units derived from the nitrogen-containing compounds,

wherein an amount of the modified butadiene rubber is 5 to 45% by weight per 100% by weight of the rubber component, and

wherein an amount of the silica is 10 to 150 parts by weight per 100 parts by weight of the rubber component.

2. The rubber composition according to claim 1 ,

wherein the modified butadiene rubber has at least one terminal further modified with a modifying agent having a functional group that contains at least one atom selected from the group consisting of nitrogen, oxygen and silicon.

3. A tire comprising

a tread prepared using the rubber composition according to claim 1 .

4. The rubber composition according to claim 1 , wherein R 0 and R 8 to R 14 each represent hydrogen, a C 1-5 aliphatic hydrocarbon group, a C 3-10 alicyclic hydrocarbon group, or a C 5-10 aromatic hydrocarbon group, and

wherein R 4 to R 7 each represent hydrogen, a C 1-10 aliphatic hydrocarbon group, a C 3-10 alicyclic hydrocarbon group, a C 5-10 aromatic hydrocarbon group, or a heterocyclic group containing 3 to 10 annular atoms.

5. The rubber composition according to claim 1 , wherein R 0 and R 8 to R 14 are each hydrogen or a C 1-2 aliphatic hydrocarbon group, and

wherein R 4 to R 7 are each a C 1-10 aliphatic hydrocarbon group, a C 5-10 aromatic hydrocarbon group, or a heterocyclic group containing 3 to 10 annular atoms.

6. The rubber composition according to claim 1 , where 1 represents an integer of 3 to 7 and m and n each represent an integer of 1 to 6.

7. The rubber composition according to claim 1 , wherein the amount of the nitrogen-containing compound in the modified butadiene rubber is 0.05 to 30% by weight.

8. The rubber composition according to claim 1 , wherein the weight-average molecular weight of the modified butadiene rubber is 1.0×10 5 to 2.0×10 6 .

9. The rubber composition according to claim 1 , further comprising 2 to 40 parts by weight of carbon black per 100 parts by weight of the rubber component.

10. The rubber composition according to claim 9 , wherein the nitrogen adsorption specific surface area of the carbon black is 30 to 100 m 2 /g.