A single-screw extruder for changing a morphology of superabsorbent polymer, specifically for a superabsorbent polymer gel (SAP polymer gel), having: - an input aperture for the introduction of SAP polymer gel, - connected to the input aperture, a channel, - arranged in the channel, a screw for conveying, and changing the morphology of, the SAP polymer gel and - connected to the channel, an output aperture for the discharge of the SAP polymer gel with changed morphology, where the screw has a shank and has screw flights arranged on the shank and is arranged and configured to convey the SAP polymer gel from the input aperture to the output aperture by means of the screw flights, where the channel has an input zone arranged at, or in the vicinity of, the input aperture, an output zone arranged at, or in the vicinity of, the output aperture, and a conveying zone extending along the channel from the input zone to the output zone, where - the screw has a pitch value of a pitch of the screw flights along the conveying zone of the channel, and - the channel has at least one mixing-element arrangement with at least one mixing element which protrudes into the channel of the single-screw extruder and which is configured for the mixing of the SAP polymer gel, wherein - the channel has at least two pins arranged along the channel in the conveying direction and separated from one another by a mixing-element separation, and there is negative correlation between a value of the mixing-element separation (K1, K2, K3, K4) and a pitch value (G1, G2, G3) of the pitch of the screw flights, namely the negative correlation between the mixing-element separation and the pitch is such that a smaller value of the mixing-element separation (K1, K2, K3, K4, K5) is provided when a larger pitch value (G1, G2, G3) is provided, and a larger value of the mixing-element separation (K1, K2, K3, K4, K5) is provided when a smaller pitch value (G1, G2, G3) is provided. - an input aperture for the introduction of SAP polymer gel, - connected to the input aperture, a channel, - arranged in the channel, a screw for conveying, and changing the morphology of, the SAP polymer gel and - connected to the channel, an output aperture for the discharge of the SAP polymer gel with changed morphology, where the screw has a shank and has screw flights arranged on the shank and is arranged and configured to convey the SAP polymer gel from the input aperture to the output aperture by means of the screw flights, where the channel has an input zone arranged at, or in the vicinity of, the input aperture, an output zone arranged at, or in the vicinity of, the output aperture, and a conveying zone extending along the channel from the input zone to the output zone, where where the screw has a shank and has screw flights arranged on the shank and is arranged and configured to convey the SAP polymer gel from the input aperture to the output aperture by means of the screw flights, where the channel has an input zone arranged at, or in the vicinity of, the input aperture, an output zone arranged at, or in the vicinity of, the output aperture, and a conveying zone extending along the channel from the input zone to the output zone, where - the screw has a pitch value of a pitch of the screw flights along the conveying zone of the channel, and - the channel has at least one mixing-element arrangement with at least one mixing element which protrudes into the channel of the single-screw extruder and which is configured for the mixing of the SAP polymer gel, - the channel has at least two pins arranged along the channel in the conveying direction and separated from one another by a mixing-element separation, and there is negative correlation between a value of the mixing-element separation (K1, K2, K3, K4) and a pitch value (G1, G2, G3) of the pitch of the screw flights, namely the negative correlation between the mixing-element separation and the pitch is such that a smaller value of the mixing-element separation (K1, K2, K3, K4, K5) is provided when a larger pitch value (G1, G2, G3) is provided, and a larger value of the mixing-element separation (K1, K2, K3, K4, K5) is provided when a smaller pitch value (G1, G2, G3) is provided.