Prepolymers with alkoxysilane end groups

A prepolymer (A) having end groups of the formula [1]

• -A-CH2—SiR1a(OR2)3-a [1],
• where
• A is a divalent linking group selected from the group consisting of —O—, —S—, —(R3)—, —O—CO—N(R3)—, —N(R3)—CO—O—, —NH—CO—NH—, —N(R4)—CO—NH—, —NH—CO—N(R4)—, and —N(R4)—CO—N(R4)—,
• R1 is an optionally halogen-substituted alkyl, cycloalkyl, alkenyl or aryl radical having 1-10 carbon atoms,
• R2 is an alkyl radical having 1-6 carbon atoms or an ω-oxyalkyl-alkyl radical having in all 2-10 carbon atoms,
• R3 is hydrogen, an optionally halogen-substituted cyclic, linear or branched C1 to C18 alkyl radical or alkenyl radical or a C6 to C18 aryl radical,
• R4 is an optionally halogen-substituted cyclic, linear or branched C1 to C18 alkyl radical or alkenyl radical or a C6 to C18 aryl radical, and
• a has the value 0, 1 or 2,
• the prepolymer (A) prepared by reacting isocyanate-functional prepolymers (A1) with alkoxysilanes (A2) possessing at least one isocyanate-reactive group,
• and optionally further components,
• with the proviso that the alkoxysilanes (A2) are employed in excess, so that the mol ratio of isocyanate-reactive groups to isocyanate groups is at least 1.2:1.