Method and apparatus for mixing viscous materials

A method of mixing viscous, shear sensitive materials in a double mixing container comprising the steps of:

• interacting the material between a pair of oppositely driven shafts in the mixing container, with working tools so that mechanical forces are applied through these working tools to move individual particles and layers of material, in oblique directions, the resultant force having component forces exerted in directions circularly, laterally, and toward the center of the container;
• randomly dividing the individual particles by means of the working tool and imparting varying velocity and velocity paths to the particles so as to promote constant and positive recirculation of all particles of the batch;
• radially inverting the individual particles of the material so as to change its direction, path of travel and velocity so that mechanical shear forces imparted by the working tool, as well as hydraulic shear forces created by the particles of the material slipping on each other by their different velocities, are averaged over an extremely short period of time;
• averaging and making uniform the shear stresses resulting from the mechanical and hydraulic shear forces, for each particle, whereby as a result of the uniform work input, uniform temperature gradient, uniform shear stress, a uniform and predictable viscosity throughout the complete batch of shear sensitive material is provided.