Use of moldings whose length·width·height dimensions are always in the range from 1 mm to 5 cm, produced by treatment of (a) open-cell foam whose density is in the range from 5 to 500 kg/m3 and whose average pore diameter is in the range from 1 μm to 1 mm (b) with an aqueous formulation of at least one cationic polymer (c) and a shaping step, as dust binders in vacuum cleaners.