Compositions and methods for metal pre-treatment

A polyurethane polymer which is obtained by

• (i) preparing at least one isocyanate-functional prepolymer (A) by reacting a mixture comprising at least one polyisocyanate (B) and at least one alkanolamine (C);
• and
• (ii) subsequently reacting the at least one isocyanate-functional prepolymer (A) with at least one compound of general formula (I),
• wherein,
• R1, R2, R3 and R4, independent of each other, are selected from the group consisting of hydrogen, —C(═O)—OH, —C(═O)—OM3, —SO3H, —SO3M3, —H, —OM3, —C(═O)—H, —C1-6-alkyl, —F, —Cl, —CN, —Br, —NH2, —NHR and —NRR′, wherein at least one of R1, R2, R3 and R4 is selected from the group consisting of —NH2 and —NHR
• M1 is selected from the group consisting of hydrogen and metal cations selected from the group consisting of lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), francium (Fr), beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and radium (Ra),
• M2 is selected from the group consisting of hydrogen and metal cations selected from the group consisting of lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), francium (Fr), beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and radium (Ra),
• M3 are, identical or different, a metal cation selected from the group consisting of lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), francium (Fr),
• beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and radium (Ra), and
• R and R′ are, identical or different, linear or branched, unsubstituted C1-C6 alkyl;
• wherein the at least one polyisocyanate (B) is selected from the group consisting of aliphatic polyisocyanates.