A self-crosslinking, branched polyurethane preparable by reacting

• (A) at least one hydroxyl-terminated polyester with a number-average molecular weight of from 500 to 4000 daltons, containing based on the polyester (A)
  • (a1) from 60 to 95% by weight of structural units derived from aliphatic starting products and
  • (a2) from 5 to 40% by weight of structural units derived from aromatic starting products

    with

• (B) at least one partially blocked polyisocyanate containing on average per molecule more than 1.5 and less than 3 free isocyanate groups,

  the equivalents ratio of free isocyanate groups in the polyisocyanate (B) to hydroxyl groups in the polyester (A) being 1, to give an isocyanato-terminated polyurethane prepolymer which is chain-extended and/or blocked with

• (C) at least one compound containing on average per molecule at least two isocyanate-reactive functional groups;

  process for its preparation, and its use as a binder in coating materials, adhesives, and sealing compounds.