Rubber composition for tread and pneumatic tire using the same

Abstract

The present invention provides a rubber composition for a tread, in which both wet grip performance and low heat generating properties can be achieved while maintaining the excellent properties of epoxidized natural rubber such as mechanical properties and abrasion resistance, and a pneumatic tire using the rubber composition. Specifically, the present invention relates to a rubber composition for a tread comprising 5 to 150 parts by weight of silica having nitrogen-adsorbing specific surface area of 100 to 300 m 2 /g and/or carbon black having nitrogen-adsorbing specific surface area of 70 to 300 m 2 /g, based on 100 parts of a rubber component containing 5 to 100% by weight of a modified epoxidized natural rubber obtained by reacting epoxidized natural rubber with a compound selected from the group consisting of a Lewis acid, an amine compound, a thiol compound, an amide compound and an imidazole compound to conduct ring opening of an epoxy group, and a pneumatic tire comprising the rubber composition for a tread.

What is claimed is:  
     
         1 . A rubber composition for a tread comprising 5 to 150 parts by weight of silica having nitrogen-adsorbing specific surface area of 100 to 300 m 2 /g and/or carbon black having nitrogen-adsorbing specific surface area of 70 to 300 m 2 /g,  
       based on 100 parts of a rubber component containing 5 to 100% by weight of a modified epoxidized natural rubber obtained by reacting epoxidized natural rubber with a compound selected from the group consisting of a Lewis acid, an amine compound, a thiol compound, an amide compound and an imidazole compound to conduct ring opening of an epoxy group.  
     
     
         2 . The rubber composition for a tread of  claim 1 , wherein a silane coupling agent is contained in an amount of at most 20% by weight based on silica.  
     
     
         3 . The rubber composition for a tread of  claim 2 , wherein said silane coupling agent is represented by the following formula (1)  
       (C n H 2n+1 O) 3 —Si—(CH 2 ) m —S 1 —(CH 2 ) m —Si—(C n H 2n+1 O) 3   (1)  
       (in said formula (1), n is an integer of 1 to 3, m is an integer of 1 to 4, 1 is the number of sulfur atoms in the polysulfide part and the average value of 1 is 2.1 to 4.5).  
     
     
         4 . The rubber composition for a tread of  claim 1 , wherein the epoxidization degree of said epoxidized natural rubber is 5 to 80% by mol.  
     
     
         5 . The rubber composition for a tread of  claim 1 , wherein said Lewis acid is selected from the group consisting of alcohol, a phenol compound, a carboxylic acid and an acid anhydride.  
     
     
         6 . The rubber composition for a tread of  claim 1 , wherein the modification degree of said modified epoxidized natural rubber is 5 to 60%.  
     
     
         7 . The rubber composition for a tread of  claim 1 , wherein the protein content of said modified epoxidized natural rubber is at most 0.1% by weight converted to nitrogen content.  
     
     
         8 . A pneumatic tire comprising the rubber composition for a tread of  claim 1.