Abstract: A device for mixing, milling or kneading feed materials, such as plastics and fillers, including a pair of spaced apart upper and lower discs defining therebetween a mixing zone. Each disc has an operating surface and is adapted so that by rotation of one of the discs, a relative motion between the two operating surfaces may be maintained. A collecting ring with a groove extending along the inner surface thereof is provided around the periphery of the mixing zone to define an annular passage which is in fluid communication with the mixing zone and which is open at one end and closed at the other end. By rotation of one of the discs, the mixed product is collected in the passage, displaced therethrough and discharged from the open end portion or scraped off at the closed portion for recovery.