Copolycondensate obtainable by copolycondensation of • at least one 1,2-C 4 -C 8 cycloalkanedicarboxylic acid, 1,3-C 4 -C 8 cycloalkanedicarboxylic acid or 1,4-C 4 -C 8 cycloalkanedicarboxylic acid, or an ester, anhydride or acid chloride thereof; • from 0.3 to 0.8 mol based on 1 mol of C 4 -C 8 cycloalkanedicarboxylic acid, of at least one 1,2-C 6 -C 12 cycloalkanediamine, 1,3-C 6 -C 12 cycloalkanediamine or 1,4-C 6 -C 12 cycloalkanediamine, or of a latent form thereof; • from 0.2 to 0.6 mol based on 1 mol of C 4 -C 8 cycloalkanedicarboxylic acid, of at least one 1,2-C 2 -C 6 alkanediol, 1,3-C 2 -C 6 alkanediol or 1,4-C 2 -C 6 alkanediol, of which from 0 to 0.05 mol of one hydroxyl group may be esterified with a monocarboxylic acid, where the C 2 -C 6 alkanediol may be uninterrupted or interrupted by -O-, with the proviso that no carbon atom of the C 2 -C 6 alkanediol is bonded to more than one oxygen atom; • optionally from 0 to 0.1 mol based on 1 mol of C 4 -C 8 cycloalkanedicarboxylic acid, of one or more amino acids; • optionally from 0 to 0.1 mol based on 1 mol of C 4 -C 8 cycloalkanedicarboxylic acid, of one or more monofunctional components selected from the group consisting of monoalcohols, primary monoamines and monoacids each containing from 1 to 18 carbon atoms; and • from 0.001 to 0.15 mol based on 1 mol of C 4 -C 8 cycloalkanedicarboxylic acid, of at least one colourant which has at least two substituents selected from the group consisting of chlorosulphonyl, 4-chloro-3-oxo-2-azabutyl (chloroacetaminomethyl) and 3,5-dicarboxyphenyl (containing 2 reactive carboxyl groups), with the proviso that at least two of these substituents must be removed from one another to such an extent that they are not condensable with one another to form a fewer than 10-membered intramolecular ring; with the proviso that the molar ratio of the total amount of all hydroxyl and primary amino groups or latent forms thereof to the total amount of all carboxyl and sulpho groups is from 5:4 to 4:5. • at least one 1,2-C 4 -C 8 cycloalkanedicarboxylic acid, 1,3-C 4 -C 8 cycloalkanedicarboxylic acid or 1,4-C 4 -C 8 cycloalkanedicarboxylic acid, or an ester, anhydride or acid chloride thereof; • from 0.3 to 0.8 mol based on 1 mol of C 4 -C 8 cycloalkanedicarboxylic acid, of at least one 1,2-C 6 -C 12 cycloalkanediamine, 1,3-C 6 -C 12 cycloalkanediamine or 1,4-C 6 -C 12 cycloalkanediamine, or of a latent form thereof; • from 0.2 to 0.6 mol based on 1 mol of C 4 -C 8 cycloalkanedicarboxylic acid, of at least one 1,2-C 2 -C 6 alkanediol, 1,3-C 2 -C 6 alkanediol or 1,4-C 2 -C 6 alkanediol, of which from 0 to 0.05 mol of one hydroxyl group may be esterified with a monocarboxylic acid, where the C 2 -C 6 alkanediol may be uninterrupted or interrupted by -O-, with the proviso that no carbon atom of the C 2 -C 6 alkanediol is bonded to more than one oxygen atom; • optionally from 0 to 0.1 mol based on 1 mol of C 4 -C 8 cycloalkanedicarboxylic acid, of one or more amino acids; • optionally from 0 to 0.1 mol based on 1 mol of C 4 -C 8 cycloalkanedicarboxylic acid, of one or more monofunctional components selected from the group consisting of monoalcohols, primary monoamines and monoacids each containing from 1 to 18 carbon atoms; and • from 0.001 to 0.15 mol based on 1 mol of C 4 -C 8 cycloalkanedicarboxylic acid, of at least one colourant which has at least two substituents selected from the group consisting of chlorosulphonyl, 4-chloro-3-oxo-2-azabutyl (chloroacetaminomethyl) and 3,5-dicarboxyphenyl (containing 2 reactive carboxyl groups), with the proviso that at least two of these substituents must be removed from one another to such an extent that they are not condensable with one another to form a fewer than 10-membered intramolecular ring;