the invention provides cross - linkable polymer powder compositions containing a ) at least one water - soluble polyhydroxy compound ; b ) at least one boric acid complex compound which is of limited solubility in water that is , it has a water solubility of less than 10 g per liter at normal conditions ; and optionally c ) a water - soluble film - forming polymer consisting of one or more free - radical polymerizable , ethylenically unsaturated monomers . the compositions are useful as a constituent in adhesives , plaster , jointing mortars , paints and binders for coating compositions , textiles , paper and the like .