Use of a combination of a functionalised organosilane-based compound and a coupling activator as a coupling system in dienic elastomer compositions containing a white filler

Use of a combination based on:

• (i) at least one coupling agent chosen from the group of coupling agents each member of which is a compound essentially consisting of a functionalized organosilane of formula:
• 10
• in which:
• the symbols R1, which are identical or different, each represent a monovalent hydrocarbon group chosen from:
• a linear or branched alkyl radical having from 1 to 4 carbon atoms;
• a linear or branched alkoxyalkyl radical having from 2 to 6 carbon atoms;
• a cycloalkyl radical having from 5 to 8 carbon atoms;
• and a phenyl radical;
• the symbols R2, which are identical or different, each represent a monovalent hydrocarbon group chosen from:
• a linear or branched alkyl radical having from 1 to 6 carbon atoms;
• a cycloalkyl radical having from 5 to 8 carbon atoms;
• and a phenyl radical;
• Z is a functional group, comprising an activated ethylenic double bond (functional group X) intended to be grafted onto the diene elastomer(s) during the vulcanization step by forming a covalent bond with this (these) elastomer(s), especially a functional group chosen from:
• a maleamic and/or fumaramic acid functional group Z2 of formula:
• 11
• an acrylamde functional group Z3 of formula:
• 12
• an acrylic functional group Z4 of formula:
• 13
• an isomaleimide functional group Z5 of formula:
• 14
• in which formulae:
• R3 is a divalent, linear or branched, alkylene hydrocarbon radical having from 1 to 10 carbon atoms, possibly interrupted by at least one oxygen-substituted heteroatom whose free valency carried by a carbon atom is linked to the Si atom;
• the symbols R4, R5, R6 and R7, which are identical to or different from one another, each represent a hydrogen atom or a monovalent hydrocarbon group chosen from:
• a linear or branched alkyl radical having from 1 to 6 carbon atoms;
• and a phenyl radical;
• a is a number chosen between 1, 2 and 3;
• and (2i) from 0.05 to a value less than 1 part by weight, per 100 parts by weight of diene elastomer(s), of at least one coupling activator consisting of a radical initiator of the type of those with thermal initiation;
• → as a white-filler/elastomer coupling system in the compositions comprising:
• (3i) at least one diene elastomer chosen from:
• homopolymers obtained by the polymerization of a diene monomer carrying two conjugated or unconjugated ethylenic double bonds;
• copolymers obtained by the copolymerization of at least two conjugated or unconjugated dienes or by the copolymerization of one or more conjugated or unconjugated dienes with one or more ethylenically unsaturated monomers;
• natural rubber;
• copolymers obtained by the copolymerization of isobutene and isoprane, and the halogenated versions of these copolymers;
• and a mixture of the aforementioned elastomers together;
• and (4i) a white filler as reinforcing filler.