Rubber composition based on a highly saturated diene elastomer
View Patent ↗A rubber composition is based on at least an elastomer matrix comprising more than 50 phr of a copolymer containing ethylene units and 1,3-diene units, the ethylene units in the copolymer representing more than 50 mol % of the monomer units of the copolymer; a 1,3-dipolar compound corresponding to the formula “Q-Sp-B” in which Q comprises a dipole containing at least and preferably one nitrogen atom, Sp, which is preferably divalent, is an atom or a group of atoms connecting Q to B, and B comprises a specific imidazole ring; a filler comprising predominantly silica and a crosslinking system comprising at least one radical polymerization initiator, and a co-crosslinking agent selected from the group consisting of (meth)acrylate compounds, maleimide compounds, allyl compounds, vinyl compounds and mixtures thereof.
1 . A rubber composition based on at least:
an elastomer matrix comprising more than 50 phr of a copolymer containing ethylene units and 1,3-diene units, the ethylene units in the copolymer representing more than 50 mol % of monomer units of the copolymer;
a 1,3-dipolar compound corresponding to formula (I)
Q-Sp-B (I),
in which Q comprises a dipole containing at least one nitrogen atom, Sp is an atom or a group of atoms connecting Q to B, and B comprises an imidazole ring corresponding to formula (II)
in which three of Z, Y, R and R′, which are identical or different, each represent an atom or a group of atoms, it being possible for Z and Y to form, together with the carbon atoms to which they are attached, a ring, and the fourth of Z, Y, R or R′ denotes a direct attachment to Sp;
a filler comprising predominantly silica; and
a crosslinking system comprising at least one radical polymerization initiator and a co-crosslinking agent selected from the group consisting of (meth)acrylate compounds, maleimide compounds, allyl compounds, vinyl compounds and mixtures thereof;
wherein the copolymer containing ethylene units and 1,3-diene units is a copolymer of ethylene and of 1,3-diene, and
wherein a content of co-crosslinking agent is within a range extending from 1 to 20 phr.
2 . The rubber composition according to claim 1 , wherein R′ denotes a direct attachment to Sp, Z and Y are each a hydrogen atom, and R represents a hydrogen atom or a carbon-based group which can contain at least one heteroatom.
3 . The rubber composition according to claim 1 , wherein Sp is a group containing up to 20 carbon atoms and which can contain at least one heteroatom.
4 . The rubber composition according to claim 1 , wherein the 1,3-dipolar compound is selected from the group consisting of nitrile oxides, nitrile imines and nitrones.
5 . The rubber composition according to claim 1 , wherein Q comprises a unit corresponding to formula (V):
in which four of symbols X 1 to X 5 , which are identical or different, are each an atom or a group of atoms, and the fifth symbol denotes a direct attachment to Sp, it being known that X 1 and X 5 are not hydrogen atoms.
6 . The rubber composition according to claim 1 , wherein the 1,3-dipolar compound is 2,4,6-trim ethyl-3-((2-methyl-1H-imidazol-1-yl)methyl)benzonitrile oxide or 2,4,6-tri ethyl-3-((2-methyl-1H-imidazol-1-yl)methyl)benzonitrile oxide.
7 . The rubber composition according to claim 1 , wherein a content of the 1,3-dipolar compound is between 0.1 and 3 molar equivalents of imidazole ring per 100 mol of monomer units constituting the copolymer.
8 . The rubber composition according to claim 1 , wherein the at least one radical polymerization initiator is an organic peroxide selected from the group consisting of dicumyl peroxide, aryl or diaryl peroxides, diacetyl peroxide, benzoyl peroxide, dibenzoyl peroxide, di(tert-butyl) peroxide, tert-butyl cumyl peroxide, 2,5-bis(tert-butylperoxy)-2,5-dimethylhexane, n-butyl 4,4′-di(tert-butylperoxy)valerate, 00-(t-butyl)O-(2-ethylhexyl) monoperoxycarbonate, tert-butyl peroxyisopropyl carbonate, tert-butyl peroxybenzoate, tert-butyl peroxy-3,5,5-trimethylhexanoate, 1,3(4)-bis(tert-butylperoxyisopropyl)benzene and mixtures thereof.
9 . The rubber composition according to claim 1 , wherein a content of the at least one radical polymerization initiator is within a range extending from 0.1 to 3 phr.
10 . The rubber composition according to claim 1 , wherein the co-crosslinking agent comprises an acrylate derivative of formula (VIII):
[X] p A (VIII),
in which [X]p corresponds to a radical of formula (IX):
in which R 1 , R 2 and R 3 independently represent a hydrogen atom or a C 1 -C 8 hydrocarbon group selected from the group consisting of alkyl groups which are linear, branched or cyclic, alkylaryl groups, aryl groups and aralkyls, and which are optionally interrupted by one or more heteroatoms, it being possible for R 2 and R 3 together to form a non-aromatic ring,
(*) represents a point of attachment of the radical of formula (IX) to A,
A represents an atom belonging to the group consisting of alkaline earth metals or transition metals, a carbon atom or a C 1 -C 30 hydrocarbon group, optionally interrupted and/or substituted by one or more heteroatoms, and
A comprises p free valencies, p having a value ranging from 2 to 6,
it being understood that X radicals are identical or different.
11 . The rubber composition according to claim 10 , wherein, in the acrylate derivative of formula (VIII), A represents an atom belonging to the group consisting of alkaline earth metals and transition metals, a carbon atom or a C 1 -C 13 hydrocarbon group, and A comprises p free valencies, p having a value ranging from 2 to 4, it being understood that X radicals are identical or different.
12 . The rubber composition according to claim 10 , wherein R 1 , R 2 and R 3 represent, independently of one another, a hydrogen atom, a methyl group or an ethyl group.
13 . A pneumatic or non-pneumatic tire comprising a rubber composition according to claim 1 .
14 . The pneumatic or non-pneumatic tire according to claim 13 , wherein the rubber composition is present in a tread of the tire.