Abstract: Provided are a viscosity stabilizer comprising carbon black and/or silica and further blended with at least one selected from the group consisting of a plasticizer, a processing aid, a softening agent and a dispersant, a viscosity-stabilized natural rubber composition blended with the viscosity stabilizer described above in an amount of 5 to 80 parts by weight per 100 parts by weight of natural rubber, a process for producing a viscosity-stabilized natural rubber composition, which comprises adding the viscosity stabilizer described above to natural rubber in producing a natural rubber master batch, and a method of controlling a rise in the viscosity of natural rubber, which comprises adding the viscosity stabilizer described above to natural rubber in producing a natural rubber master batch.

Abstract: In a method of controlling a tire vulcanization by controlling a heat supply to a vulcanizing machine including a mold unit and a bladder unit, temperatures at points on a boundary between the mold unit and a tire are measured by means of temperature sensors, a temperature at a center post assembly of the bladder unit is measured by a temperature sensor arranged at the center post assembly. The method includes calculating temperature profiles within the tire from the measured temperatures by using the finite difference method, estimating vulcanization profiles within the tire from the temperature profile, deriving the least vulcanization within the tire from the vulcanization profiles, and producing a stop signal for the heat supply to the vulcanizing machine in accordance with the least vulcanization thus derived.