Sulfur-crosslinkable rubber composition comprising a graft copolymer
The present invention relates to a sulfur-crosslinkable rubber composition comprising a filler component in an amount in the range of 1 to 350 phr, and at least one graft copolymer having a modified diene rubber backbone and one or more oligomeric side chains grafted to the modified diene rubber backbone, wherein the oligomeric side chains are obtained through reversible addition fragmentation chain transfer polymerization of a monomer composition, and wherein the monomer composition comprises at least one polar monomer.
1 . Sulfur-crosslinkable rubber composition comprising:
a filler component in an amount in the range of 1 to 350 phr,
at least one graft copolymer having a modified diene rubber backbone and one or more oligomeric side chains grafted to the modified diene rubber backbone, and wherein the oligomeric side chains are obtained through reversible addition fragmentation chain transfer polymerization of a monomer composition, and wherein the monomer composition comprises at least one polar monomer,
wherein the monomer composition comprises at least one methacrylate monomer, as at least one polar monomer, and the monomer composition comprises at least one aromatic hydrocarbon monomer with a vinyl moiety, as at least one unsaturated hydrocarbon monomer,
wherein the at least one methacrylate monomer includes 2-(dimethylamino)ethyl methacrylate and the at least one aromatic hydrocarbon monomer with a vinyl moiety includes styrene, the 2-(dimethylamino)ethyl methacrylate and styrene being present in a combined amount of 50% or more by weight, with respect to the weight of the monomer composition.
2 . Sulfur-crosslinkable rubber composition according to claim 1 , wherein in the monomer composition the weight ratio of polar monomers to unsaturated hydrocarbon monomers is in the range of 5:1 to 1:5.
3 . Sulfur-crosslinkable rubber composition according to claim 1 , wherein the oligomeric side chains have a weight average molecular weight Mw in the range of 350 g/mol to 40000 g/mol.
4 . Sulfur-crosslinkable rubber composition according to claim 1 , wherein the oligomeric side chains have a general structure according to formula I):
wherein R1, R2 and R6 are each independently selected from the group consisting of hydrogen and alkyl groups having from 1 to 20 carbon atoms, R3 is a substituted or unsubstituted alkyl chain having from 1 to 20 carbon atoms and R4 and R5 are each independently selected from the group consisting of substituted or unsubstituted alkyl groups having from 1 to 20 carbon atoms, substituted or unsubstituted cycloalkyl groups having from 3 to 20 carbon atoms and substituted or unsubstituted aryl groups having from 6 to 30 carbon atoms, wherein the repeating units are statistically distributed in the oligomer chain and wherein a and b are each independently integers in the range of 1 to 200.
5 . Sulfur-crosslinkable rubber composition according to claim 4 , wherein R1, R2, R4 and R5 are each independently selected from the group consisting of alkyl groups having 1 carbon atom, R3 is an unsubstituted alkyl chain having 2 carbon atoms, R6 is hydrogen and wherein a and b are each independently integers in the range of 2 to 50, wherein the oligomeric side chain has an average value a in the range of 18 to 23, and an average value b in the range of 3 to 8.
6 . Sulfur-crosslinkable rubber composition according to claim 1 , wherein the graft copolymer has an average grafting density expressed as number of side chains per modified diene rubber backbone, in the range of 2 to 8.
7 . Sulfur-crosslinkable rubber composition according to claim 1 , wherein the graft copolymer has a polydispersity in the range of 1.1 to 2.5, and wherein the ratio of the polydispersity of the graft copolymer to the polydispersity of the unmodified diene rubber compound is in the range of 1 to 1.5.
8 . Sulfur-crosslinkable rubber composition according to claim 1 , wherein the graft copolymer has a weight average molecular weight Mw in the range of 400000 to 800000 g/mol.
9 . Sulfur-crosslinkable rubber composition according to claim 1 , wherein the modified diene rubber backbone is obtained by living anionic polymerization, wherein the modified diene rubber backbone is modified styrene-butadiene rubber.
10 . Sulfur-crosslinkable rubber composition according to claim 1 , comprising the filler component in an amount of 10 to 300 phr, wherein the filler component comprises silica and/or carbon black.
11 . Sulfur-vulcanized rubber composition obtainable through sulfur-vulcanization of a sulfur-crosslinkable rubber composition according to claim 1 .
12 . Vehicle tire, comprising the sulfur-vulcanized rubber composition according to claim 11 .
13 . A method of using graft copolymer having a modified diene rubber backbone and one or more oligomeric side chains grafted to the modified diene rubber backbone, comprising: providing the graft copolymer and using the graft copolymer in a sulfur-crosslinkable rubber composition according to claim 1 , for increasing the rolling resistance of vehicle tires produced from the sulfur-crosslinkable rubber composition, wherein the oligomeric side chains are obtained through reversible addition fragmentation chain transfer polymerization of a monomer composition, wherein the monomer composition comprises at least one polar monomer.
14 . Sulfur-crosslinkable rubber composition according to claim 1 , wherein in the monomer composition the weight ratio of polar monomers to unsaturated hydrocarbon monomers is in the range of 4:1 to 1:4.
15 . Sulfur-crosslinkable rubber composition according to claim 14 , wherein the number of repeating units in the side chain is in the range of 2 to 400 units, the graft copolymer has a polydispersity in the range of 1.2 to 2.0, and wherein the ratio of the polydispersity of the graft copolymer to the polydispersity of the unmodified diene rubber compound is in the range of 1.05 to 1.2.
16 . Sulfur-crosslinkable rubber composition according to claim 1 , wherein the filler component comprises silica in an amount of 90% or more by weight with respect to the weight of the filler component.