Rubber composition and pneumatic tire using same

1. A rubber composition comprising:

a sulfur-crosslinkable diene rubber:

from 1 to 100 parts by mass of carbon black and/or from 5 to 150 parts by mass of an inorganic filler;

from 0.5 to 30 parts by mass of a sulfur-containing compounding agent; and

from 0.01 to 20 parts by mass of a boron compound and/or a boron complex based on 100 parts by mass of the sulfur-crosslinkable diene rubber,

wherein the boron compound is represented by Formula (1):

 where R 1 , R 2 , and R 3 are each independently an optionally substituted

hydrocarbon group having from 1 to 20 carbon atoms, a hydroxy group, an alkoxy group having from 1 to 20 carbon atoms, an ester group having from 1 to 20 carbon atoms, an amino group, an amino group having one or two hydrocarbon groups with from 1 to 20 carbon atoms, a halogen, or hydrogen; and

R 1 , R 2 , and R 3 may be the same or different;

the boron complex is at least one compound selected from the group consisting of Formula (2), Formula (3), and Formula (6);

Formula (2) is given by:

 where:

R 4 and R 5 are each independently an optionally substituted hydrocarbon group having from 1 to 20 carbon atoms, a hydroxy group, an alkoxy group having from 1 to 20 carbon atoms, an ester group having from 1 to 20 carbon atoms, an amino group, an amino group having 1 or 2 hydrocarbon groups with from 1 to 20 carbon atoms, or a halogen;

m and n are each independently an integer from 0 to 5;

R 4 may be the same or different when n is a plural number; and

R 5 may be the same or different when m is a number greater than 1, Formula (3) is given by:

R 6 a H 3-a N—BH 3-b R 7 b

 where:

each R 6 is independently an optionally substituted aliphatic hydrocarbon group having from 1 to 20 carbon atoms;

R 7 is each independently an optionally substituted hydrocarbon group; a is an integer from 1 to 3; and b is an integer from 0 to 3;

R 6 may be the same or different when a is 2 or 3; and

R 7 may be the same or different when b is 2 or 3;

and Formula (6) is given by:

H 3 N—BH 3-b R 7 b

where:

each R 7 is independently an optionally substituted hydrocarbon group; and

b is an integer from 0 to 3; and

R 7 may be the same or different when b is 2 or 3.

2. The rubber composition according to claim 1 , wherein:

the inorganic filler is silica; and

the sulfur-containing compounding agent comprises at least a sulfur-containing silane coupling agent in an amount from 0.5 to 20 parts by mass per 100 parts by mass of the diene rubber; and a ratio of the boron compound and/or boron complex to sulfur-containing silane coupling agent is from 0.01:1 to 3:1.

3. The rubber composition according to claim 1 , wherein said sulfur containing compounding agent being at least one selected from the group consisting of sulfur, sulfur-containing silane coupling agents, and sulfur-containing vulcanization accelerators.

4. The rubber composition according to claim 1 , wherein:

said inorganic filler is silica;

said sulfur-containing compounding agent containing at least a sulfur-containing silane coupling agent; and

the amount of the sulfur-containing silane coupling agent is from 1 to 20 parts by mass per 100 parts by mass of the sulfur crosslinkable diene rubber.

5. The rubber composition according to claim 1 , wherein:

the amount of the inorganic filler is from 10 to 150 parts by mass;

the amount of the sulfur-containing compounding agent is from 1 to 30 parts by mass; and

the amount of the boron compound and/or complex is from 0.1 to 20 parts by mass per 100 parts by mass of the sulfur crosslinkable diene rubber.

6. The rubber composition according to claim 5 , wherein the sulfur-containing compounding agent is at least one selected from the group consisting of sulfur, sulfur-containing silane coupling agents, and sulfur-containing vulcanization accelerators.

7. The rubber composition according to 5 , wherein:

the inorganic filler is silica;

the sulfur-containing compounding agent comprises at least a sulfur-containing silane coupling agent; and

the amount of the sulfur-containing silane coupling agent is from 1 to 20 parts by mass per 100 parts by mass of the sulfur crosslinkable diene rubber.

8. A pneumatic tire comprising at least one of a capped tread, a side wall, a belt, an inner liner, a carcass, or a bead formed from the rubber composition of claim 1 .

9. A pneumatic tire comprising at least one of a capped tread, a side wall, a belt, an inner liner, a carcass, or a bead formed from the rubber composition of claim 2 .

10. A pneumatic tire comprising at least one of a capped tread, a side wall, a belt, an inner liner, a carcass, or a bead formed from the rubber composition of claim 5 .

11. A pneumatic tire comprising at least one of a capped tread, a side wall, a belt, an inner liner, a carcass, or a bead formed from the rubber composition of claim 6 .

12. A pneumatic tire comprising at least one of a capped tread, a side wall, a belt, an inner liner, a carcass, or a bead formed from the rubber composition of claim 7 .