Patent ID: 7179875

Claim:
A process for preparing water-absorbent resins, which comprises: a) obtaining crude acrylic acid by either a1) absorbing acrylic acid from the reaction gases obtained from the catalytic gas-phase oxidation of propane, propylene and/or acrolein in an absorption liquid and isolating crude acrylic acid from the absorption liquid laden with acrylic acid, or a2) separating a crude acrylic acid fraction from said reaction gases by fractional condensation and, optionally, purifying the condensed fraction of acrylic acid by crystallization, b) treating the crude acrylic acid obtained from a1) or a2) with an aldehyde scavenger, c) separating pure acrylic acid from the treated crude acrylic acid by distillation, and d) polymerizing the pure acrylic acid, optionally after partial neutralization, alone or in admixture with other ethylenically unsaturated monomers, under free-radical polymerization conditions, wherein the isolation of the pure acrylic acid by distillation is conducted without reflux of condensate by thermally separating the treated crude acrylic acid into vapor comprising acrylic acid and a residue and quantitatively condensing the vapor to obtain pure acrylic acid, no fraction boiling lower than the pure acrylic acid fraction being isolated.