The invention generally relates to a process for the preparation of water-absorbent polymer particles, comprising the process steps of (i) preparing an aqueous monomer solution comprising at least one partially neutralized, monoethylenically unsaturated monomer bearing carboxylic acid groups (α1) and at least one crosslinker (α3) (ii) optionally adding fine particles of a water-absorbent polymer to the aqueous monomer solution (iii) adding a polymerization initiator or a at least one component of a polymerization initiator system that comprises two or more components to the aqueous monomer solution (iv) optionally decreasing the oxygen content of the aqueous monomer solution (v) charging the aqueous monomer solution onto a belt of a polymerization belt reactor (vi) polymerizing the monomers in the aqueous monomer solution on the belt, thereby obtaining a polymer gel (vii) discharging the polymer gel out of the polymerization belt reactor and optionally comminuting the polymer gel (viii) drying the optionally comminuted polymer gel (ix) grinding the dried polymer gel thereby obtaining water-absorbent polymer particles (x) sizing the grinded water-absorbent polymer particles and (xi) optionally treating the surface of the grinded and sized water-absorbent polymer particles wherein the belt is shaped as a trough extending longitudinally over at least 30 % of a longitudinal extension of the belt wherein the trough comprises a first part and a further part.Linvention se rapporte, de manière générale, à un procédé permettant la préparation de particules polymères absorbant leau, ledit procédé comprenant les étapes de traitement consistant à : (i) préparer une solution aqueuse de monomère comprenant au moins un monomère à insaturation monoéthylénique partiellement neutralisé, portant des groupes acide carboxylique (α1) et au moins un agent de réticulation (α3) (ii) ajouter facultativement de fines particules dun polymère absorbant leau à la solution aqueuse de monomère (
