A mixer (1) for mixing a mixing material (13) in polymer processing comprises a mixing chamber (2) and more than two rotors (6a-6d) arranged in the mixing chamber (2). In particular, the rotors (6a-6d) can be configured to interlock.

A mixing and extrusion machine (10) for the manufacture of rubber mixtures has a mixer with a converging conical twin screw (12) with a fixed frame (14) that supports sleeves (16). Two screws (18), being mounted at an angle, are mounted in the mixer (12) so as to move in translational movement between an opening (22) arranged upstream and an outlet (25) arranged downstream of the sleeves, so that the thread tips of each screw contact tangentially the surfaces of the opposite screw so that the screws remain substantially in contact with each other when the screws rotate at an angle and at a center distance that facilitates self-cleaning. The screw threads maintain tangential contact with the inner surfaces of the sleeves, thus preventing the retention of mixing material on these surfaces.

The kneading rotor according to one aspect of the present disclosure is a kneading rotor for a kneading machine, comprising a base made of carbon steel or alloy steel for machine structure, a padded layer made of austenitic stainless steel on at least part of a surface of the base and has a hard chromium plated layer on at least part of a surface of the padded layer.

An internal mixer includes a mixing chamber having a mixing room, a material input portion located above the mixing chamber, a weight, a driving device that raises and lowers the weight between a lower position where the weight can press a material to be kneaded in the mixing room from above and a retraction position where the weight is retracted upward from the lower position, a mixing rotor that kneads the material to be kneaded in the mixing room, and an exhausting device having an inner end portion facing the mixing room and provided in the mixing chamber and configured to be able to discharge gas generated during kneading of the material to be kneaded from the inner end to the outside of the mixing chamber.