Use of water-absorbent, predominantly open-celled crosslinked acid-functional addition polymer foams in hygiene articles

A method of preparing a water-absorbent open-celled crosslinked acid-functional hydrogel foam comprising:

• (a) preparing a polymerizable aqueous mixture containing
• (i) from 10 to 80%, by weight, of acid-functional monoethylenically unsaturated monomers which are partially neutralized,
• (ii) optionally up to 50%, by weight, of other monoethylenically unsaturated monomers,
• (iii) from 0.001 to 5%, by weight, of a crosslinker,
• (iv) at least one initiator, and
• (v) from 0.1 to 20%, by weight, of at least one surfactant;
• (b) foaming the polymerizable aqueous mixture of step (a);
• (c) polymerizing the foamed mixture of step (b) to form a hydrogel foam;
• then
• (d) applying to a surface of the hydrogel foam of step (c) at least one surfactant and optionally a finely divided silicon dioxide, wherein an amount of the surfactant on the surface of the hydrogel foam is in the range from 0.1 to 10% by weight, based on the weight of the foam.