The present invention relates to fluorocarbon polymer-free preparations (Z) based on water and/or organic solvents and their use as a finish on flat materials, containing (1) 10-90% of a reaction product (S) prepared by reacting a component (A) with a partially blocked or non-blocked di-, tri- or polyisocyanate (IC) and (2) 10-90% of a C8-C28-alkyl groups containing organopolysiloxane, (3) 0-45% of a blocked or non-blocked di-, tri- or polyisocyanate, and (4) if appropriate customary emulsifiers. When used as a finish on flat materials, the preparations endow the treated flat materials with durable hydrophobic properties.