Abstract: The invention relates to the use of an apparatus for adding at least one solid or viscous liquid additive, or an additive dispersed in solvent, to a reactor interior of a reactor for preparing crosslinked, finely divided polymers by copolymerizing (a) water-soluble, monoethylenically unsaturated monomers and (b) from 0.001 to 5 mol %, based on the monomers (a), of monomers comprising at least two polymerizable groups, (c) from 0 to 20 mol %, based on the monomers (a), of water-insoluble monoethylenically unsaturated monomers, where the apparatus comprises at least one screw for conveying the at least one additive and the at least one screw ends in an addition orifice substantially flush with the inner wall of the reactor interior.

Abstract: The disclosed device is directed towards a mixer apparatus comprising a barrel defining an interior and an exterior. The barrel has a first end and a second end opposite thereof. The barrel defines at least one inlet proximate to the first end and an outlet proximate to the second end. A motor unit is in operative communication with the barrel. A moving element is disposed in the interior of the barrel. The moving element is configured to move material through the barrel to the outlet of the barrel. At least one first mixing element is fluidly coupled to the outlet.