Rubber Composition for Tire Including a Novel Anti-oxidant System

Abstract

Rubber composition, especially for a tyre, based on at least one diene elastomer, a reinforcing filler, a crosslinking system and an antioxidant system, wherein the antioxidant system has at least two antioxidants “A” and “B”: A. an N-alkyl-N′-phenyl-para-phenylenediamine corresponding to the formula (I): B. a 4,4′,4″-tris(1,3-dimethylbutylamino)triphenylamine corresponding to the specific formula: wherein R 1 represents a linear or branched alkyl group having from 1 to 12 carbon atoms or a cycloalkyl group having from 5 to 8 carbon atoms, the A/B weight ratio being between 1/10 and 5/1.

1 . A rubber composition based on at least one diene elastomer, a reinforcing filler, a crosslinking system and an antioxidant system, wherein said antioxidant system comprises at least two antioxidants “A” and “B”:
 A. an N-alkyl-N′-phenyl-para-phenylenediamine corresponding to the formula (I): 
 
       
         
           
           
               
               
           
         
         B. a 4,4′,4″-tris(1,3-dimethylbutylamino)triphenylamine corresponding to the specific formula: 
       
       
         
           
           
               
               
           
         
         wherein R 1  represents a linear or branched alkyl group having from 1 to 12 carbon atoms or a cycloalkyl group having from 5 to 8 carbon atoms, the A/B weight ratio being between 1/10 and 5/1. 
       
     
     
         2 . The composition of  claim 1 , wherein R 1  represents an alkyl group having from 2 to 8 carbon atoms or a cyclohexyl group. 
     
     
         3 . The composition of  claim 2 , wherein R 1  represents an alkyl group chosen from the group composed of isopropyl, 1,3-dimethylbutyl and 1,4-dimethylpentyl. 
     
     
         4 . The composition of  claim 3 , wherein antioxidant A is N-isopropyl-N′-phenyl-para-phenylenediamine corresponding to the formula (III-a): 
       
         
           
           
               
               
           
         
       
     
     
         5 . The composition of  claim 3 , wherein antioxidant A is N-1,3-dimethylbutyl-N′-phenyl-para-phenylenediamine corresponding to the formula (III-b): 
       
         
           
           
               
               
           
         
       
     
     
         6 . (canceled) 
     
     
         7 . (canceled) 
     
     
         8 . The composition of  claim 1 , wherein the content of each antioxidant A and B is between 0.5 and 5 phr. 
     
     
         9 . The composition of  claim 1 , wherein the A/B weight ratio is between 1/7 and 4/1. 
     
     
         10 . The composition of  claim 1 , wherein the diene elastomer is chosen from the group formed by polybutadienes, natural rubber, synthetic polyisoprenes, butadiene copolymers, isoprene copolymers and blends of these elastomers. 
     
     
         11 . The composition of  claim 10 , wherein the diene elastomer is an isoprene elastomer. 
     
     
         12 . The composition of  claim 11 , wherein the isoprene elastomer is chosen from the group composed of natural rubber, synthetic cis-1,4-polyisoprenes, isoprene copolymers and blends of these elastomers. 
     
     
         13 . The composition of  claim 12 , wherein the isoprene elastomer is natural rubber. 
     
     
         14 . (canceled) 
     
     
         15 . An antioxidant system that can be used for the anti-ageing protection of a rubber composition for a tire, wherein said system comprises at least two antioxidants “A” and “B”:
 A. an N-alkyl-N′-phenyl-para-phenylenediamine corresponding to the formula (I): 
 
       
         
           
           
               
               
           
         
         B. a 4,4′,4″-tris(1,3-dimethylbutylamino)triphenylamine corresponding to the specific formula: 
       
       
         
           
           
               
               
           
         
         wherein R 1  represents a linear or branched alkyl group having from 1 to 12 carbon atoms or a cycloalkyl group having from 5 to 8 carbon atoms, the A/B weight ratio being between 0.1 and 5.0. 
       
     
     
         16 . (canceled) 
     
     
         17 . A tire comprising the rubber composition of  claim 1 . 
     
     
         18 . The tire of  claim 17 , said tire being a heavy vehicle tire. 
     
     
         19 . The tire of  claim 17 , wherein the rubber composition is in the belt of said tire. 
     
     
         20 . A process for preparing a rubber composition based on at least one diene elastomer, a reinforcing filler, a crosslinking system and an antioxidant system, said process comprising the steps of:
 a. incorporating into a diene elastomer, in a mixer:
 (i) a reinforcing filler; and 
 (ii) an antioxidant system, 
 by thermomechanically kneading the entire mixture, in one or more stages, until a maximum temperature between 110° C. and 190° C. is reached; 
   b. cooling the entire mixture to a temperature below 100° C.;   c. then incorporating a crosslinking system;   d. kneading the entire mixture up to a maximum temperature below 110° C., and being characterized in that said antioxidant system comprises at least two antioxidants “A” and “B”:   A. an N-alkyl-N′-phenyl-para-phenylenediamine corresponding to the formula (I):   
       
         
           
           
               
               
           
         
         B. a 4,4′,4″-tris(1,3-dimethylbutylamino)triphenylamine corresponding to the specific formula: 
       
       
         
           
           
               
               
           
         
         wherein R 1  represents a linear or branched alkyl group having from 1 to 12 carbon atoms or a cycloalkyl group having from 5 to 8 carbon atoms, the A/B weight ratio being between 0.1 and 5.0. 
       
     
     
         21 . The composition of  claim 8 , wherein the content of each antioxidant A and B is between 0.5 and 3 phr.