Elastomer mixture mainly comprising a diene elastomer coupled by an aminoalkoxysilane group, rubber composition including the same and methods for obtaining same
The present invention relates to an elastomer mixture resulting from the modification of a diene elastomer by a coupling agent that introduces, into the elastomer chain, an alkoxysilane group bearing a tertiary or secondary amine functional group. This mixture predominantly comprises the diene elastomer coupled by the alkoxysilane group bearing a tertiary or secondary amine functional group which is bonded to the diene elastomer through the silicon atom. The invention also relates to a reinforced rubber composition, in particular that can be used for the manufacture of tires, which comprises a reinforcing filler and an elastomer matrix comprising at least this elastomer mixture, and to its preparation process. This composition has improved hysteresis and mechanical properties in the vulcanized state, and also improved processing in the uncured state.
1. An elastomer mixture resulting from the modification of a diene elastomer by a coupling agent that introduces, into the elastomer chain, an alkoxysilane group bearing a tertiary or secondary amine functional group, wherein the elastomer mixture predominantly comprises the diene elastomer having the alkoxysilane group bearing a tertiary or secondary amine functional group within its polymer chain, the silicon atom of this aminoalkoxysilane group bonding two chains of the diene elastomer.
2. The elastomer mixture according to claim 1 , wherein the diene elastomer coupled by the alkoxysilane group bearing a tertiary or secondary amine functional group, bonded to the diene elastomer through the silicon atom corresponds to one of the formulae (I) to (III) below:
wherein:
the symbol E denotes a diene elastomer;
R 1 denotes a linear or branched, C 1 -C 10 alkyl radical, a C 5 -C 18 cycloalkyl radical, a C 6 -C 18 aryl radical or a C 7 -C 18 aralkyl radical;
R 2 is a linear or branched, divalent, hydrocarbon-based C 1 -C 10 alkyl, C 6 -C 18 aryl or C 7 -C 18 aralkyl derivative;
in formula (I), R 3 and R 4 , which are identical or different, represent a hydrogen atom or a C 1 -C 10 alkyl radical, on condition that when one of R 3 and R 4 represents a hydrogen atom the other is different, or else R 3 and R 4 form, with N to which they are bonded, a heterocycle containing a nitrogen atom and at least one carbon atom;
in formula (II), R 5 represents a linear or branched, C 1 -C 10 alkylidene radical;
in formula (III), the symbols A denote, independently of one another, a nitrogen atom or a carbon atom, on condition that at least one of the symbols A denotes a nitrogen atom.
3. The elastomer mixture according to claim 2 , wherein, in the formulae (I), (II) and (III), R 1 represents a methyl or ethyl radical.
4. The elastomer mixture according to claim 2 , wherein, in the formulae (I), (II) and (III), R 2 represents the propane-1,3-diyl radical.
5. The elastomer mixture according claim 2 , wherein the diene elastomer coupled by the alkoxysilane group bearing a tertiary or secondary amine functional group, bonded to the diene elastomer by the silicon atom corresponds to the formula (I) in which R 3 and R 4 , which are identical or different, represent a methyl or ethyl radical.
6. The elastomer mixture according to claim 2 , wherein the diene elastomer coupled by the alkoxysilane group bearing a tertiary or secondary amine functional group, bonded to the diene elastomer by the silicon atom corresponds to the formula (II) in which R 5 represents a linear or branched, C 4 -C 6 alkylidene radical.
7. The elastomer mixture according to claim 6 , wherein the diene elastomer coupled by the alkoxysilane group bearing a tertiary or secondary amine functional group, bonded to the diene elastomer by the silicon atom corresponds to the formula (II) in which R 5 represents the 3-(1,3-dimethylbutylidene) radical.
8. The elastomer mixture according to claim 2 , wherein the diene elastomer coupled by the alkoxysilane group bearing a tertiary or secondary amine functional group, bonded to the diene elastomer by the silicon atom corresponds to the formula (III) in which a single A denotes a nitrogen atom and is located in the meta or para position of the ring relative to the alkoxysilane group.
9. The elastomer mixture according to claim 1 , wherein the modified diene elastomer is derived from a butadiene/vinyl aromatic copolymer prepared in solution.
10. The elastomer mixture according to claim 1 , comprising at least 75% by weight of diene elastomer coupled by the aminoalkoxysilane group, relative to the total weight of the mixture.
11. A process for preparing an elastomer mixture as defined in claim 1 , comprising:
(i) in a first stage, reacting one or more monomers for forming a diene polymer optionally in the presence or absence of an inert hydrocarbon solvent, with a polymerization initiator to produce a living diene polymer, and
(ii) in a second stage, reacting the living diene polymer obtained with a coupling agent that introduces, into the elastomer chain, an alkoxysilane group bearing a tertiary or secondary amine functional group, with a molar ratio of coupling agent/initiator ranging from 0.4 to 0.6.
12. A reinforced rubber composition based on at least one reinforcing filler and an elastomer matrix comprising at least one elastomer mixture as defined in claim 1 .
13. The rubber composition according to claim 12 , wherein the elastomer matrix predominantly comprises the elastomer mixture.
14. The rubber composition according to claim 13 , wherein the elastomer matrix is constituted of the elastomer.
15. The rubber composition according to claim 12 , wherein said reinforcing filler comprises a reinforcing organic filler in a weight fraction ranging from 50% to 100% of the rubber composition.
16. The rubber composition according to claim 15 , wherein the reinforcing organic filler is carbon black.
17. The rubber composition according to claim 12 , wherein said reinforcing filler comprises a reinforcing inorganic filler in a weight fraction greater than 50% and ranging up to 100%.
18. The rubber composition according to claim 17 , wherein the reinforcing inorganic filler is silica.
19. A process for preparing a composition according to claim 12 , comprising:
(i) in a first stage, preparing an elastomer mixture by reacting one or more monomers for forming a diene polymer, optionally in the presence or absence of an inert hydrocarbon solvent, with a polymerization initiator to produce a living diene polymer, and reacting, in a second stage, the living diene polymer obtained from the first stage with a coupling agent with a molar ratio of coupling agent/initiator ranging from 0.4 to 0.6, thereby obtaining predominantly a diene elastomer coupled by an alkoxysilane group bearing a tertiary or secondary amine functional group which is bonded to the diene elastomer by the silicon atom,
(ii) carrying out, at a maximum temperature of between 130 ° C. and 200 ° C., a first step of thermomechanical working of the constituents of the composition comprising the coupled diene elastomer having an alkoxysilane group bearing a tertiary or secondary amine functional group in the middle of the chain and a reinforcing filler, in the absence of a crosslinking system, then
(iii) carrying out, at a temperature below said maximum temperature of said first step, a second step of mechanical working during which said crosslinking system is incorporated.
20. A tire tread, comprising a crosslinkable or crosslinked rubber composition prepared according to the process of claim 12 .
21. A tire tread according to claim 20 , constituted of said crosslinkable or crosslinked rubber composition.
22. A tire, comprising a tire tread according to claim 20 .