A copolymer based on ethylenically unsaturated monomers containing monomer units of surface-active urethane derivatives with ethylenically unsaturated carboxyl or carbamido radicals and units of ethylenically unsaturated monomers capable of salt formation and having been prepared by free-radical-initiated copolymerization in solution, emulsion, suspension or by bead copolymerization or solutions or aqueous dispersions thereof or the salts thereof or solutions or dispersions of the salts, wherein the copolymer particles, relative to the total amount of monomer units in the copolymer in % by weight, have been synthesized from
- (a) 25 to 85% by weight of ethylenically unsaturated hydrophobic monomers from the group comprising vinyl esters of (C.sub.1 -C.sub.18)-monocarboxylic acids, acrylic esters or (meth)acrylic esters of (C.sub.1 -C.sub.22)-alcohols, vinyl aromatics having up to 18 carbon atoms, vinyl chloride, ethylene, acrylonitrile or (meth)acrylonitrile, diesters of maleic acid and/or fumaric acid with (C.sub.1 -C.sub.22)-alcohols, vinylpyrrolidone, and p1 (b) 1 to 50% by weight of ethylenically unsaturated monomers capable of salt formation and containing functional anionic radicals from the group comprising --COOH, sulfonic acids or sulfonic acid derivatives or phosphonic acids or phosphonic acid derivatives, carboxylic acids from the group comprising ethylenically unsaturated (C.sub.3 -C.sub.5)-mono- or dicarboxylic acids, and monoesters of dibasic carboxylic acids with straight-chain or branched (C.sub.1 -C.sub.8)-alcohols, furthermore monomers from the group comprising vinylsulfonic acid, (3-sulfopropyl)methacrylic esters, acrylamidomethylpropanesulfonic acid, vinylphosphonic acid, acrylamidomethylpropanephosphonic acid or salts thereof, or instead of anionic monomers, ethylenically unsaturated monomers capable of salt formation and containing functional cationic radicals from the group comprising --NR.sup.5 R.sup.6, where R.sup.5 and R.sup.6 can be identical or different and be H or (C.sub.1 -C.sub.18)-alkyl, or R.sup.5 and R.sup.6 together with N can form a five- to seven-membered heterocyclic ring, or ethylenically unsaturated (C.sub.3 -C.sub.18)-aliphatic primary amines or secondary amines containing a (C.sub.1 -C.sub.18)-alkyl radical or tertiary amines containing two (C.sub.1 -C.sub.18)-alkyl radicals, and
- (c) 0.1 to 30% by weight of ethylenically unsaturated surface-active urethane derivatives of the formula I, ##STR10## in which the radicals R.sup.1 to R.sup.4 and Z and the numbered indices x, y and k have the following meanings:
- R.sup.1, R.sup.2, R.sup.3, which can be identical or different, are H, --CH.sub.3, --COOH, --CH.sub.2 --COOH,
- Z is oxygen or NH,
- x, y, k, which can be identical or different, are 0 to 100, with the proviso that x+y+k.gtoreq.2,
- R.sup.4 is (C.sub.1 -C.sub.30)-alkyl which may be substituted, (C.sub.8 -C.sub.10)-aryl which may be substituted, (C.sub.7 -C.sub.30)-aralkyl which may be substituted, (C.sub.5 -C.sub.8)-cycloalkyl which may be substituted, a 5- to 7-membered heterocycle which may be substituted,
- and
- (d) 0 to 10% by weight of further ethylenically unsaturated monomers different from (a) to (c) and having functional radicals from the group comprising ##STR11## where R.sup.7 and r.sup.8 can be identical or different and are H, (C.sub.1 -C.sub.6 -alkyl, (C.sub.2 -C.sub.8)-alkoxyalkyl, (C.sub.5 -C.sub.7)-cycloalkyl or (C.sub.6 -C.sub.18)-aralkyl, or R.sup.7 and R.sup.8 together with N form a five- to seven-membered heterocyclic ring, or ethylenically unsaturated hydroxyalkyl esters or polyalkyleneoxide esters of acrylic acid or (meth)acrylic acid, in which the terminal OH groups of the ester or polyalkylene glycol ether radicals can also be etherified or esterified, ethylenically unsaturated amides, and
- (e) 0 to 5% by weight of ethylenically unsaturated carbonyl compounds, and
- (f) 0 to 5% by weight of ethylenically polyunsaturated or polyfunctional monomers capable of crosslinking, and
- (g) 0 to 5% by weight of molecular weight regulators from the group comprising dodecylmercaptan, carbon tetrachloride, .alpha.-methylstyrene, toluene, bromotrichloromethane, tetrakis(mercaptoacetyl)pentaerythritol, thioglycolic acid,
- and when aqueous dispersions or the copolymers isolated therefrom are present, they furthermore contain
- (h) 0.1 to 10% by weight, relative to the total amount of all monomer units in the copolymer, emulsifiers and/or protective colloids.