The invention relates to an apparatus and a process for producing pigment-containing, in particular carbon-black-containing, polymer mixtures comprising polycarbonates and optionally elastomers, and/or other components, where the mouldings produced therefrom have, after the shaping process via injection moulding or via extrusion, improved surface properties and improved mechanical properties.

An intermittent extrusion system and an extrusion device are disclosed. The intermittent extrusion system includes a barrel and an extrusion unit. The extrusion unit includes a first screw and a second screw, both the first screw and the second screw are installed in the barrel and can rotate in the barrel, a screw thread of the first screw can mesh with a screw groove of the second screw, the first screw has at least one thread start, and the second screw has at least one thread start. The first screw rotates at a constant speed, while the second screw rotates intermittently, and a rotating direction of the first screw is opposite to that of the second screw.