Abstract: A zwitterionic polyamine comprising a linear or branched hydrophobic polyamine backbone having 2 to 10 tertiary amino nitrogen atoms and a spacer between two tertiary nitrogen atoms wherein the spacer is, for example selected from C8-C16-alkylene, C5-C15-cyloalkylene, wherein in formula (IV) R═C1- to C22-alkyl or C7-C22-aralkyl and n=3 to 6, at least one tertiary amine end group of the polyamine backbone contains two groups having formula (V) or (VI), wherein A means an ethylene oxide unit, a propylene oxide unit, a unit of butylene oxides and a tetrahydrofuran unit, n is a number of from 1 to 50, X is an anionic group such as —SO3M, with the proviso that in formula (VI) one X may also be hydrogen and M is hydrogen, alkai metal or ammonium, or contains one group of formula (V) or (VI) and one group selected from radicals consisting of formula (VII), C1- to C22-alkyl and C7-C22-aralkyl the meaning of A and n is the same as in formula (V) or (VI), said zwitterionic polyetherpolyamine having a