Rubber compositions comprising organosilicon coupling agents and inorganic fillers

A rubber composition which comprises an isoprene elastomer and having incorporated therein:

• (A) an effective amount of a polyfunctional coupling agent system having at least two functions designated “X” or “Y”, which may be grafted onto the elastomer by means of the function “X”, and onto the inorganic filler by means of the function “Y”;
• (B) at least one elastomer of rubber type, natural or synthetic;
• (C) an inorganic filler as reinforcing filler;
• (D) all or part of other constituents or additives selected from the group consisting of one or more curing agent(s) (D1), optionally, one or more curing accelerator(s) (D2), optionally, one or more curing activator(s) (D3), optionally, one or more non-white reinforcing filler(s) (D4), optionally, one or more non-reinforcing or sparingly reinforcing inorganic filler(s) (D5), optionally, one or more protecting agent(s) (D6), optionally, one or more plasticizer(s) (D7), and mixtures thereof;
• wherein said polyfunctional coupling agent system (A) comprising the combination of coupling agents in which each is a compound consisting essentially of a functionalized organosilicon compound selected from the group consisting of the following compounds (i) and (2i):
• (i) compounds comprising at least one functionalized siloxane oligomer corresponding to the following formula (I):
• [(G0)3SiO1/2]m[(G0)2SiO2/2]n[G0SiO3/2]o[SiO4/2]p[(G2)a(G1)a′(Z—CO—N═N—CO-A) SiO(3-a-a′)/2]q (I)
• in which:
• a represents an integer selected from 0, 1 and 2;
• a′ represents an integer selected from 0, 1 and 2;
• the sum a+a′ ranges from 0 to 2, with the condition according to which when a=0, then at least one of the symbols G0 has the definition below for G2;
• either at least one of m, n, o and p is an integer or fraction other than 0 (zero) and q represents an integer or fraction greater than or equal to 1, or q is greater than 1 and each of the m, n, o and p has any value;
• the symbols G0, which may be identical or different, each represent one of the groups corresponding to G2 or G1;
• the symbols G2, which may be identical or different, each represent a hydroxyl group or a hydrolyzable monovalent group;
• the symbols G1, which may be identical or different, each represent a saturated or unsaturated aliphatic hydrocarbon-based group;
• a saturated or unsaturated and/or aromatic, monocyclic or polycyclic carbocyclic group;
• or a group representing a saturated or unsaturated aliphatic hydrocarbon-based moiety and a carbocyclic moiety as defined above;
• with the proviso that a group G1 may together form, with a group G2 and the silicon atom from which G1 and G2 depend, a monocyclic or polycyclic carbocyclic group having from 2 to 10 ring carbon atoms and optionally comprising one or more ring oxygen heteroatom(s);
• the symbol Z represents a divalent radical selected from:
• a saturated or unsaturated aliphatic hydrocarbon-based group;
• a saturated, unsaturated and/or aromatic, monocyclic or polycyclic carbocyclic group;
• and a group containing a saturated or unsaturated aliphatic hydrocarbon-based moiety and a carbocyclic moiety as defined above;
• said divalent radical being optionally substituted or interrupted with an oxygen atom and/or a sulfur atom and/or a nitrogen atom, said nitrogen atom, if present, bearing one monovalent group selected from:
• a hydrogen atom;
• a saturated or unsaturated aliphatic hydrocarbon-based atom;
• a saturated or unsaturated and/or aromatic, monocyclic or polycyclic carbocyclic group;
• and a group containing a saturated or unsaturated aliphatic hydrocarbon-based moiety and a carbocyclic moiety as defined above;
• the symbol A represents:
• a saturated or unsaturated aliphatic hydrocarbon-based group;
• a saturated or unsaturated and/or aromatic, monocyclic or polycyclic carbocyclic group;
• or a group representing a saturated or unsaturated aliphatic hydrocarbon-based moiety and a carbocyclic moiety as defined above;
• a group —X-G3 in which:
• X represents —O—, —S— or —NG4- wherein G4 is as defined above for G1;
• G3, which may be identical to or different from G4, represents any of the groups G1;
• with the proviso that the substituents G3 and G4 of the group —NG4G3 may together from, with the nitrogen atom from which they depend, a single 5- to 7-membered ring having from 3 to 6 carbon atoms, 1 or 2 nitrogen atom(s) and, optionally, 1 or 2 unsaturated double bond(s);
• or, when q=1, a group:
• —[—Z—SiO(3-a-a′)/2(G2)a(G1)a′][(G0)3SiO1/2]m [(G0)2SiO2/2]n [G0SiO3/2]o [SiO4/2]p
• in which the symbols Z, G1, G2, G0′, a, a′, m, n, o and p have the definitions given above;
• and
• (2i) compounds comprising a mixture of at least one functionalized siloxane (i) with (3i) at least one functionalized organosilane corresponding to the formula (I) in which m=n=o=p=0 (zero), q=1, a is an integer selected from 0, 1, 2 and 3 and the sum a+a′=3.