Functional diene elastomer and rubber composition
A diene elastomer and a rubber composition comprising the diene elastomer is provided. The diene elastomer bears pendent imidazole functions in a molar content of at most 4% of the constituent repeating units of the diene elastomer, which diene elastomer is a copolymer of ethylene and of a 1,3-diene comprising ethylene units, the ethylene units representing at least 50 mol % of the constituent repeating units of the diene elastomer, the 1,3-diene being 1,3-butadiene or isoprene. Such an elastomer confers improved uncured properties on the rubber composition.
1. A diene elastomer bearing pendant imidazole functions in a molar content of at least 0.05 to 4 mol % of the constituent repeating units of the diene elastomer, wherein the diene elastomer is a copolymer of ethylene and of 1,3-butadiene which contains units of formula (I) or formula (II)
the ethylene units representing at least 50 mol % of the constituent repeating units of the diene elastomer, and wherein the pendant imidazole functions are of formula (III)
in which the symbols Y 1 , Y 2 , Y 3 and Y 4 , which may be identical or different, represent a hydrogen or a substituent, and one of the symbols Y 1 , Y 2 , Y 3 and Y 4 denotes an attachment to a diene unit which is one of a plurality of diene units of the diene elastomer, a portion of the diene units of the diene elastomer are modified by grafting a modifying agent which contains a group that is reactive with respect to carbon-carbon double bonds and a group of formula (IV)
in which the symbols Z 1 , Z 2 , Z 3 and Z 4 , which may be identical or different, represent a hydrogen atom or a substituent, and at least one of the symbols Z 1 , Z 2 , Z 3 and Z 4 denotes an attachment to the reactive group.
2. The diene elastomer according to claim 1 , in which the ethylene units represent at least 65 mol % of the constituent repeating units of the diene elastomer.
3. The diene elastomer according to claim 1 , in which Y 3 and Y 4 are each a hydrogen atom, and Y 1 is a hydrogen atom or a carbon chain.
4. The diene elastomer according to claim 1 , in which Z 3 and Z 4 each represent a hydrogen atom, and Z 1 is a hydrogen atom or a carbon chain.
5. The diene elastomer according to claim 1 , in which the modifying agent is a 1,3-dipolar compound.
6. The diene elastomer according to claim 5 , in which the 1,3-dipolar compound contains a unit of formula (V)
in which four of the six symbols R 1 to R 6 , which may be identical or different, are a hydrogen atom or a substituent, wherein R 5 represents an attachment to the group of formula (IV) and R 6 represents a direct attachment to a dipole.
7. The diene elastomer according to claim 6 , in which R 1 , R 3 and R 5 each represent the substituent, and the substituent is a hydrocarbon-based group.
8. The diene elastomer according to claim 6 , in which R 5 is attached to the group of formula (IV) via a carbon chain.
9. A rubber composition which comprises the diene elastomer defined in claim 1 and a reinforcing filler which comprises a carbon black, a silica or a mixture of a carbon black and a silica.
10. A tire which comprises the rubber composition defined in claim 9 .
11. The diene elastomer according to claim 2 , in which the ethylene units represent at least 70 mol % of the constituent repeating units of the diene elastomer.
12. The diene elastomer according to claim 1 , wherein the symbol Y 2 denotes an attachment to a diene unit of the diene elastomer.
13. The diene elastomer according to claim 3 , in which Y 1 is an alkyl group.
14. The diene elastomer according to claim 1 , in which the symbol Z 2 denotes an attachment to the reactive group.