Patent ID: 8206027

Claim:
A method 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, wherein the at least one solid or viscous liquid additive is added by an apparatus comprising 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, and wherein (i) between the screw and the reactor is arranged a pin against which the screw falls in the event of fracture or (ii) the interior of the screw accommodates a pin, by means of which a spring is prestressed with the weight of the screw in such a way that, in the event of part of the screw breaking off, the pin, owing to the low weight of the screw, as a result of the spring force of the prestressed spring, impacts against a sensor by means of which the reactor is stopped.