Aqueous coating compositions and their use for the preparation of coatings that are permeable to water vapor

A coating composition used for the preparation of coatings having a water vapor permeability of at least 2500 g/m.sup.2 per day using the DS 2109 TM1 method comprising

• (A) a polyurethane containing (1) from 0.1 to 75 meq per 100 g of polyurethane (A) of ionic groups and (2) 11 to 50% by weight, based on polyurethane (A), of polyethylene oxide --(CH.sub.2 CH.sub.2 O).sub.n -- units having a sequence length n of from 2 to 25 incorporated into the main chain, wherein said polyurethane (A) is prepared from reactive components comprising
• (I) one or more polyisocyanates,
• (II) one or more polyols having a number average molecular weight of from 350 to 5000, with the proviso that if any such polyol is a sulfonated polyether diol having the formula ##STR6## wherein R denotes hydrogen or an organic group having 1 to 8 carbon atoms, m and n independently represent the numbers 1 to 10, p represents the numbers 0, 1, or 2, and M denotes ammonium or the cation of an alkali metal, then at least one additional polyether polyol containing ethoxy groups must also be present, and
• (III) one or more chain lengthening agents having a molecular weight of from 32 to 349;
• and
• (B) from 30 to 80% by weight, based on the sum of components (A) and (B), of an aqueous phase.