Functionalized diene elastomer, and rubber composition containing same
The present invention relates to a specific functionalized diene elastomer. This functionalized elastomer exhibits a reduced cold flow without, however, damaging the properties of a reinforced rubber composition in which it is present, in particular the processing properties and the hysteresis properties. This functionalized diene elastomer carries, at the chain end, a silanol functional group or a polysiloxane block having a silanol end and is partially coupled by or star-branched by tin.
1. A diene elastomer, wherein:
from 75% to 95% by weight of the diene elastomer is monofunctional and carries, at just one chain end, a silanol functional group or a polysiloxane block having a silanol end, the other end being devoid of any functionalization, and
from 5% to 25% by weight of the diene elastomer is coupled by or star-branched by tin.
2. The elastomer according to claim 1 , wherein the polysiloxane block having a silanol end corresponds to the formula:
[—(SiR 1 R 2 O) x —H]
wherein:
R 1 and R 2 , which are identical or different, represent an alkyl, cycloalkyl, aryl, alkaryl, aralkyl or vinyl group having from 1 to 10 carbon atoms, and
x is an integer ranging from 1 to 1500.
3. The elastomer according to claim 2 , wherein R 1 and R 2 , which are identical or different, represent an alkyl group having from 1 to 5 carbon atoms.
4. The elastomer according to claim 1 , wherein 10% to 25% by weight of the diene elastomer is the diene elastomer coupled by or star-branched by tin.
5. The elastomer according to claim 1 , wherein the diene elastomer coupled by or star-branched by tin is an elastomer star-branched by tin.
6. The elastomer according to claim 5 , wherein the diene elastomer star-branched by tin is an elastomer comprising four branches.
7. The elastomer according to claim 1 , wherein the diene elastomer is a butadiene/styrene copolymer.
8. An elastomer rubber composition based on at least one reinforcing filler comprising an inorganic filler and on an elastomer matrix, wherein the elastomer matrix comprises at least one diene elastomer according to claim 1 .
9. The composition according to claim 8 , wherein the elastomer matrix further comprises at least one conventional diene elastomer.
10. The composition according to claim 8 , wherein the proportion of inorganic filler in the reinforcing filler is greater than 50% by weight, with respect to the total weight of the reinforcing filler.
11. The composition according to claim 8 , wherein the reinforcing inorganic filler is composed of silica.
12. A semifinished article made of rubber for tires, comprising:
a crosslinkable or crosslinked rubber composition according to claim 8 .
13. A semifinished article according to claim 12 , wherein said article is a tread.
14. A tire comprising: a semifinished article according to claim 12 .
15. A process for reducing the cold flow of a monofunctional diene elastomer carrying, at just one chain end, a silanol functional group or a polysiloxane block having a silanol end, the other end being devoid of any functionalization, comprising, prior to its conditioning, modifying the monofunctional diene elastomer by adding a diene elastomer coupled by or star-branched by tin in a proportion of from 5 to 35% by weight, with respect to the weight of the monofunctional diene elastomer.
16. A process for reducing the cold flow of a monofunctional diene elastomer carrying, at just one chain end, a silanol functional group or a polysiloxane block having a silanol end, the other end being devoid of any functionalization, comprising:
on conclusion of polymerization of a diene elastomer, coupling or star-branching from 5 to 25% by weight of the living elastomer by a tin-based compound, and then
functionalizing the 75 to 95% by weight of a remaining living elastomer with a functionalization agent capable of introducing the silanol functional group or the polysiloxane block having a silanol end.