Rubber compositions
A rubber composition includes 100 parts by mass of a solid rubber (A), 0.1 to 50 parts by mass of a modified liquid diene rubber (B) having a functional group derived from a silane compound represented by the formula (1), and 20 to 200 parts by mass of a filler (C), the modified liquid diene rubber (B) satisfying (i) to (iii) below: (i) The weight average molecular weight (Mw) is 15,000 to 120,000. (ii) The vinyl content is not more than 70 mol %. (iii) The average number of functional groups per molecule of the modified liquid diene rubber (B) is 1 to 30.
1. A rubber composition comprising:
100 parts by mass of a solid rubber (A),
from 0.1 to 50 parts by mass of a modified liquid diene rubber (B) having a functional group derived from a silane compound, and
from 20 to 200 parts by mass of a filler (C),
wherein the modified liquid diene rubber (B) satisfies:
(i) a weight average molecular weight (Mw), which is a polystyrene equivalent weight average molecular weight measured by gel permeation chromatography, is 15,000 to 100,000,
(ii) a vinyl content determined by 1 H-NMR is not more than 70 mol %, and
(iii) an average number of functional groups per molecule of the modified liquid diene rubber (B), which is calculated from the functional group equivalent weight (g/eq) calculated from the ratio of the area of the peak assigned to the polymer main chains to the area of the peak assigned to the functional groups using 1 H-NMR or 13 C-NMR and the styrene equivalent number average molecular weight Mn of the modified liquid diene rubber (B), (Average number of functional groups per molecule)=[(Number average molecular weight Mn)/(Molecular weight of styrene unit)×Molar-average molecular weight of all monomer units in an average molecule of the modified liquid diene rubber)]/(Functional group equivalent weight), is from 1 to 20, and
wherein the silane compound is a compound of formula:
wherein R 1 is a C 1-6 divalent alkylene group, and
R 2 , R 3 and R 4 are each independently a methoxy group, an ethoxy group, a phenoxy group, a methyl group, an ethyl group or a phenyl group, with the proviso that at least one of R 2 , R 3 and R 4 is a methoxy group, an ethoxy group or a phenoxy group, and
wherein the modified liquid diene rubber (B) is prepared by adding the silane compound (1) to an unmodified liquid diene rubber (B′) with a radical catalyst.
2. The rubber composition according to claim 1 ,
wherein a melt viscosity of the modified liquid diene rubber (B) at 38° C. is from 1 to 4,000 Pa·s.
3. The rubber composition according to claim 1 , wherein the modified liquid diene rubber (B) is a polymer comprising a monomer unit derived from isoprene and/or butadiene.
4. The rubber composition according to claim 1 , wherein the solid rubber (A) is one or more selected from a natural rubber, a styrene butadiene rubber, a butadiene rubber and an isoprene rubber.
5. The rubber composition according to claim 1 , wherein the filler (C) is at least one selected from a carbon black and a silica.
6. A crosslinked product obtained by crosslinking the rubber composition of claim 1 .
7. A tire comprising the rubber composition of claim 1 .
8. A tire comprising the crosslinked product of claim 6 .
9. A rubber composition comprising:
100 parts by mass of a solid rubber (A),
from 0.1 to 50 parts by mass of a modified liquid diene rubber (B) having a functional group derived from a silane compound, and
from 20 to 200 parts by mass of a filler (C),
wherein the modified liquid diene rubber (B) satisfies:
(i) a weight average molecular weight (Mw), which is a polystyrene equivalent weight average molecular weight measured by gel permeation chromatography, is 15,000 to 100,000,
(ii) a vinyl content determined by 1 H-NMR is not more than 70 mol %, and
(iii) an average number of functional groups per molecule of the modified liquid diene rubber (B), which is calculated from the functional group equivalent weight (g/eq) calculated from the ratio of the area of the peak assigned to the polymer main chains to the area of the peak assigned to the functional groups using 1 H-NMR or 13 C-NMR and the styrene equivalent number average molecular weight Mn of the modified liquid diene rubber (B), (Average number of functional groups per molecule)=[(Number average molecular weight Mn)/(Molecular weight of styrene unit)×Molar-average molecular weight of all monomer units in an average molecule of the modified liquid diene rubber)]/(Functional group equivalent weight), is from 1 to 20, and
wherein the silane compound is a compound of formula:
wherein R 1 is a C 1-6 divalent alkylene group, and
R 2 , R 3 and R 4 are each independently a methoxy group, an ethoxy group, a phenoxy group, a methyl group, an ethyl group or a phenyl group, with the proviso that at least one of R 2 , R 3 and R 4 is a methoxy group, an ethoxy group or a phenoxy group.
10. The rubber composition according to claim 1 , wherein a raw material for the modified liquid diene rubber (B) is an unmodified liquid diene rubber (B′) containing 100 mass % of butadiene units.