Physical Properties of Rubber Compounds Processed by Kneaders Equipped with a New Type Rotor

摘要

Styrene-butadiene-rubber (SBR) was mixed with carbon black (CB), zinc oxide (ZnO), etc. using 10 L and 75 L kneaders equipped with a conventional rotor, and 7 L and 55 L kneaders with a new type rotor. The new type rotor used in this paper has a large diameter of rotating shaft in comparison with the conventional type rotor. These rotors were installed in the same vessels, respectively. Under the same rotating speed for the new type rotor and the conventional type rotor, that is, under the same shear rate of the tip region, the Mooney viscosity and the volume resistivity of the SBR compounds were measured at arbitrary rotor revolutions. By using the new type rotor, it is thought that not only in the tip region, called the high shear region, but also in the annulus, called the low shear region, the mixing will proceed. The Mooney viscosity of the SBR compounds obtained by the 55 L kneader with the new type rotor was lower than that by the 75 L kneader with the conventional type rotor. The volume resistivity of the SBR compounds obtained by the 55 L kneader was higher than that by the 75 L kneader. It is supposed that at the start of mixing for the 55 L kneader, most of CB was incorporated into SBR in the annulus to form the loose agglomerates of CB in the rubber. This may be due to the low shear rate. Then the agglomerates will be collapsed to the fine aggregates of CB in the rubber through the subsequent mixing.