Production process for producing water-absorbent polymer particles, wherein the production process comprises the following steps: - polymerizing (S1) an aqueous monomer solution or suspension to produce an aqueous polymer gel (S2), - drying (S3) the aqueous polymer gel in a belt dryer with a conveyor belt (400), involving receiving the aqueous polymer gel on the conveyor belt (400) and conveying the polymer gel on the conveyor belt (400) in a conveying direction (C) of the conveyor belt (400), - crushing and/or grinding (S4) the dried polymer gel into water-absorbent polymer particles, wherein, for the drying (S3): - the belt dryer has a dryer structure (101), in the internal space (101i) of which the conveyor belt (400) is run. According to the invention, it is provided that - drying air is circulated in the internal space (101i) of the dryer structure (101) in counterflow (C') to the conveying direction (C) and the internal space of the dryer structure (101) is kept largely, preferably completely, at a negative pressure (p_U) with respect to the ambient pressure (p_A) in the external space of the dryer structure (101), and the internal space (101i) has and/or forms a pressure zone (DZ), in particular is divided into a number of pressure zones (DZ), wherein, along the conveying direction (C): - a first internal pressure is formed as an inlet pressure at a polymer gel inlet (100A) in at least one of the pressure zones (DZ) with a first pressure difference (ApA) in relation to an ambient pressure (p_A), and - a second internal pressure is formed as an outlet pressure at a polymer gel outlet (100B) in the at least one pressure zone (DZ) with a second pressure difference (ApB) in relation to an ambient pressure (p_A), wherein - the second pressure difference (ApB) is less than the first pressure difference (ApA).