Tire rubber composition comprising a coupling agent having a polythiosulfenamide function

A process for preparing an elastomeric composition usable for the manufacture of tires, comprising the following steps:

• incorporating in a diene elastomer, in a mixer, at least:
• a reinforcing inorganic filler;
• as (inorganic filler/diene elastomer) coupling agent, an organosilicon compound which is at least bifunctional and can be grafted onto the elastomer by means of a sulfur group,
• thermomechanically kneading the entire mixture, in one or more stages, until a maximum temperature of between 110° C. and 190° C. is reached;
• cooling the entire mixture to a temperature of less than 100° C.;
• then incorporating a cross-linking system;
• kneading the entire mixture until a maximum temperature of less than 120° C. is reached,
• wherein said sulfur group comprises a polythiosulfenamide function and satisfies the formula:
• ≡Si-A-Sx—NR1R2, (I)
• in which:
• A is a divalent bond group, whether straight-chain or branched, which makes it possible to join the polythiosulfenamide group to a silicon atom of the organosilicon compound;
• x is an integer or fractional number of from 2 to 4;
• R1 represents hydrogen or a monovalent hydrocarbon group;
• R2 represents a monovalent hydrocarbon group selected from among C3-C8 alkyls, whether straight-chain or branched, C5-C10 cycloalkyls, C6-C18 aryls and (C6-C18)aryl-(C1-C8)alkyls;
• R1 and R2 possibly forming together and with the nitrogen atom to which they are bonded a single hydrocarbon ring.

A tire comprising an elastomeric composition based on a diene elastomer, an inorganic filler and coupling agent comprising an organosilicon compound which is at least bifunctional and can be grafted on to the elastomer by means of a sulfur group having a polythiosulfenamide function, of formula:

• ≡Si-A-SxNR1R2, (I)
• in which:
• A is a divalent bond group, whether straight-chain or branched, which makes it possible to join the polythiosulfenamide group to a silicon atom of the organosilicon compound;
• x is an integer or fractional number of from 2 to 4;
• R1 represents hydrogen or a monovalent hydrocarbon group;
• R2 represents a monovalent hydrocarbon group selected from among C3-C8 alkyls, whether straight-chain or branched, C5-C10 cycloalkyls, C6-C18 aryls and (C6-C18)aryl-(C1-C8)alkyls;
• R1 and R2 possibly forming together and with the nitrogen atom to which they are bonded a single hydrocarbon ring.

A tire tread comprising an elastomeric composition based on a diene elastomer, an inorganic filler and a coupling agent comprising an organosilicon compound which is at least bifunctional and can be grafted on to the elastomer by means of a sulfur group having a polythiosulfenamide function, of formula:

• ≡Si-A-Sx—NR1R2, (I)
• in which:
• A is a divalent bond group, whether straight-chain or branched, which makes it possible to join the polythiosulfenamide group to a silicon atom of the organosilicon compound;
• x is an integer or fractional number of from 2 to 4;
• R1 represents hydrogen or a monovalent hydrocarbon group;
• R2 represents a monovalent hydrocarbon group selected from among C3-C8 alkyls, whether straight-chain or branched, C5-C10 cycloalkyls, C6-C18 aryls and (C6-C18)aryl-(C1-C8)alkyls;
• R1 and R2 possibly forming together and with the nitrogen atom to which they are bonded a single hydrocarbon ring.