Malonic acid dyes capable of forming polycondensation products have the formula ##STR1## where R.sup.1 and R.sup.2 are each independently of the other hydroxyl, C.sub.1 -C.sub.6 -alkoxy, chlorine or bromine,R.sup.3 is hydrogen or C.sub.1 -C.sub.6 -alkyl,A is C.sub.1 -C.sub.20 -alkylene which may be interrupted by oxygen atoms or by imino or C.sub.1 -C.sub.4 -alkylimino groups, andChr is the radical of a chromophore derived from an anthraquinone, perylene, disazo or trisazo dye or else, when R.sup.3 is C.sub.1 -C.sub.6 -alkyl, from a monoazo dye.