Process for producing superabsorbents

A process for producing superabsorbent polymer particles, comprising polymerizing a monomer solution, comprising

• a) partly neutralized acrylic acid,
• b) at least one crosslinker, and
• c) at least one initiator,
• drying a resulting polymer gel, optionally grinding and optionally classifying a resulting dried polymer gel and optionally thermally post-crosslinking and cooling resulting polymer particles, wherein the partly neutralized acrylic acid is formed by continuous mixing of acrylic acid, an aqueous solution of a base, and optionally water, an apparatus for preparing the partly neutralized acrylic acid comprises a ring line (R), a vessel (B), a heat exchanger (W), and a pump (P), wherein the vessel (B) has a cylindrical shape having a diameter d and a torispherical bottom, and the torispherical bottom has a dish having a radius r1 of 0.8 to 1.2 d and a toroidal shaped knuckle having a radius r2 of 0.06 to 0.17 d.