Process for obtaining a cationic polymer with an at least bimodal molecular weight distribution

The present invention relates to a process for obtaining a cationic polymer by polymerization of at least one cationic monomer, at least one crosslinker and optionally further monomers, such as nonionic monomers, associative monomers and/or chain transfer agents. The cationic polymer has an at least bimodal molecular weight distribution with at least one first peak (P1) and at least one second peak (P2), wherein the first peak has a lower average sedimentation coefficient of ≤100 Sved and the second peak has a higher average sedimentation coefficient of ≥1000 Sved. The polymerization is carried out in two subsequent steps I) and II). In step II), the crosslinker is either completely absent or present in a very limited amount. Step II) is carried out after the polymerization of step I is finished or vice versa.