High impermeability innerliner compound and method for the production thereof

Method for the manufacture of the innerliner compound comprising: —a first mixing step wherein at least one cross-linkable unsaturated chain polymeric base and one filler system are mixed together; —a final mixing step wherein a vulcanization system is added and mixed with the mixture deriving from an earlier mixing step; and —an intermediate mixing step, interposed between said first mixing step and the final mixing step, and wherein lignin is added and mixed into the mixture deriving from a previous mixing step.