Composition comprising a) a polymer modified with at least one silane group (R 1) a b Si- in which X is selected from the group of the R 2 O-, R 2 NH-, R 2 -COO- and (R 2) 2 C=N-O- radicals, R 1 and R 2 are each independently alkyl, cycloalkyl and/or aryl, a is 0, 1 or 2, b is 1, 2 or 3 and the sum total of a and b is 3, and b) a mixture of catenated siloxanes and/or cyclic siloxanes of the general formulae I and/or II 3 Si-O-[Si 2 -O] m -Si 3, in which the individual R radicals are each independently alkoxy, alkoxyalkoxy, alkyl, alkenyl, cycloalkyl and/or aryl and some of the R radicals are aminoalkyl-functional groups of the formula -C o H 2o -NH 2, -C o H 2o -NHR', -C o H 2o -NRR', -C o H 2o -NH-C p H 2p -NH 2 or -C o H 2o -NH-C p H 2p -NH-C q H 2q -NH 2, in which R' is alkyl, cycloalkyl or aryl and R takes one of the above definitions or in which R and R' bonded to a nitrogen atom, together with the common nitrogen atom, form a five- to seven-membered heterocyclic ring, in which R' and R take one of the above definitions, o is independently integers from 1 to 6, p and q are each independently integers from 2 to 6, m is an integer from 2 to 30, n is an integer from 3 to 30, where not more than one aminoalkyl-functional group is bonded to a silicon atom in a compound of the formula I and/or II, and where the quotient of the molar ratio of Si to alkoxy radicals is at least 0.3. a) a polymer modified with at least one silane group (R 1) a b Si- in which X is selected from the group of the R 2 O-, R 2 NH-, R 2 -COO- and (R 2) 2 C=N-O- radicals, R 1 and R 2 are each independently alkyl, cycloalkyl and/or aryl, a is 0, 1 or 2, b is 1, 2 or 3 and the sum total of a and b is 3, and b) a mixture of catenated siloxanes and/or cyclic siloxanes of the general formulae I and/or II 3 Si-O-[Si 2 -O] m -Si 3, in which the individual R radicals are each independently alkoxy, alkoxyalkoxy, alkyl, alkenyl, cycloalkyl and/or aryl and some of the R radicals are aminoalkyl-functional groups of the formula -C o H 2o -NH 2, -C o H 2o -NHR', -C o H 2o -NRR', -C o H 2o -NH-C p H 2p -NH 2 or -C o H 2o -NH-C p H 2p -NH-C q H 2q -NH 2, in which R' is alkyl, cycloalkyl or aryl and R takes one of the above definitions or in which R and R' bonded to a nitrogen atom, together with the common nitrogen atom, form a five- to seven-membered heterocyclic ring, in which R' and R take one of the above definitions, o is independently integers from 1 to 6, p and q are each independently integers from 2 to 6, m is an integer from 2 to 30, n is an integer from 3 to 30, where not more than one aminoalkyl-functional group is bonded to a silicon atom in a compound of the formula I and/or II, and where the quotient of the molar ratio of Si to alkoxy radicals is at least 0.3. in which the individual R radicals are each independently alkoxy, alkoxyalkoxy, alkyl, alkenyl, cycloalkyl and/or aryl and some of the R radicals are aminoalkyl-functional groups of the formula -C o H 2o -NH 2, -C o H 2o -NHR', -C o H 2o -NRR', -C o H 2o -NH-C p H 2p -NH 2 or -C o H 2o -NH-C p H 2p -NH-C q H 2q -NH 2, in which R' is alkyl, cycloalkyl or aryl and R takes one of the above definitions or in which R and R' bonded to a nitrogen atom, together with the common nitrogen atom, form a five- to seven-membered heterocyclic ring, in which R' and R take one of the above definitions, o is independently integers from 1 to 6, p and q are each independently integers from 2 to 6, m is an integer from 2 to 30, n is an integer from 3 to 30, where not more than one aminoalkyl-functional group is bonded to a silicon atom in a compound of the formula I and/or II, and where the quotient of the molar ratio of Si to alkoxy radicals is at least 0.3.