The invention generally relates to a process (100) for the preparation of surface-crosslinked water-absorbent polymer particles (505), 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 water-absorbent polymer particles or fine surface-crosslinked water-absorbent polymer particles or both； (iii) adding a polymerization initiator or a at least one component of a polymerization initiator system； (iv) optionally decreasing the oxygen content of the aqueous monomer solution； (v) charging the aqueous monomer solution into a polymerization reactor； (vi) polymerizing the monomers, thereby obtaining a polymer gel； (vii) discharging the polymer gel out of the polymerization reactor and optionally comminuting the polymer gel； (viii) drying the polymer gel, thereby obtaining a dried polymer gel； (ix) grinding, thereby obtaining water-absorbent polymer particles； (x) subjecting the water-absorbent polymer particles to a first sizing step； (xi) adding Si-oxide, thereby obtaining treated water-absorbent polymer particles； (xii) adding a crosslinking composition and heating the treated water-absorbent polymer particles, thereby obtaining heated water-absorbent polymer particles； (xiii) drying, thereby obtaining surface-crosslinked water-absorbent polymer particles； (xiv) cooling the surface-crosslinked water-absorbent polymer particles； wherein at least one of the process steps (i) to (vi) further comprises, adding a blowing agent in an amount in a range of from 500 to 4000 ppm by weight, based on the total weight of the monoethylenically unsaturated monomers.L'invention concerne d'une façon générale un procédé (100) pour la préparation de particules de polymère absorbant l'eau réticulées en surface (505), comprenant les étapes de procédé consistant à (i) préparer une solution
