Edge separation in a turned-up end portion (5E) of a carcass ply (5) is suppressed. In a pneumatic tire comprising a bead core (4) embedded in a bead portion (3) and a carcass ply (5) turned up and locked around the bead core (4), a rubber sheet (10) is prepared using a wet masterbatch containing natural rubber and/or polyisoprene rubber and carbon black, and the rubber sheet (10) is arranged on at least one of front and back sides of the turned-up end portion (5E) of the carcass ply (5).

The present invention relates to a process for making a polymer masterbatch with silica nanoparticles highly uniformly dispersed therein by using a stable aqueous emulsion of compatibilized silica nanoparticles, the sizes of which are mechanically reduced to nanoscales. Adequate reduction of the silica particles to nanoscales is essential for the formation of a desired emulsion of highly stability. The said emulsion of compatibilized silica nanoparticle can be easily mixed under mild conditions with a polymer in latex form, which can be high purity natural rubber, synthetic rubber and/or a blend thereof. The bifunctional organosilane coupling agent bonded-Silica nanoparticles are subsequently incorporated into the rubber polymer network during coagulation with formic acid. The inventive rubber-silica masterbatch thus obtained is useful for manufacturing rubber and other polymer composite products.

Provided are a process for efficiently producing a rubber wet master batch in which a dispersibility of carbon black in the rubber is improved, in which a reinforcing property and an abrasion resistance of the rubber can be enhanced by using carbon black having a high surface activity, in which a yield of the carbon black in the wet master batch obtained is not reduced and in which a handling property of the carbon black is good as compared with master batches prepared by using a granulated and dried substance of carbon black prepared by a conventional wet method and non-granulated carbon black, a carbon black-containing rubber wet master batch obtained by the above process and a rubber composition and a tire prepared by using the master batch. It is a process for producing a rubber wet master batch comprising a step for mixing a slurry (A) in which a filler containing carbon black is dispersed with a rubber liquid (B) in which a rubber component is dispersed or dissolved, wherein the slurry (A) is prepared by using a filler containing a carbon black granulated substance which is granulated by a wet method and which stays in a non-drying state.