Method for the production of superabsorbers

Superabsorbent particles having a centrifuge retention capacity of at least 25 g/g, an absorption under a pressure of 49.2 g/cm2 of at least 15 g/g, a gel bed permeability of at least 60 darcies, and the superabsorbent particles, after storage at a temperature of 70° C. and a relative humidity of 80% for 14 days, have an L value of at least 67, an a value of less than 7.0 and a b value of less than 14.5, wherein the particles are prepared by polymerizing a monomer solution or suspension comprising

• a) at least one ethylenically unsaturated monomer which bears an acid group and optionally is at least partly neutralized,
• b) at least one crosslinker,
• c) at least one initiator,
• d) optionally one or more ethylenically unsaturated monomer copolymerizable with the monomer a) and
• e) optionally one or more water-soluble polymer, comprising
• i) polymerizing the monomer solution to give a polymer gel,
• ii) optionally comminuting the resulting polymer gel,
• iii) drying the polymer gel,
• iv) grinding and classifying the dried polymer gel to give polymer particles,
• v) thermally surface postcrosslinking the classified polymer particles,
• vi) optionally reclassifying the surface postcrosslinked polymer particles,
• vii) optionally recycling polymer particles removed in step iv) upstream of step iii) and
• viii) optionally recycling polymer particles removed in step vi) upstream of step iii),
• which comprises adding to the monomer solution prior to step i) at least 0.75% by weight of a hydroxyphosphonic acid or salts thereof, calculated on the basis of the total amount of monomer a) used, and adding to the polymer particles between step iv) and step vi) at least 0.09% by weight of aluminum cations, calculated on the basis of the total amount of polymer particles used.