A copolymer comprising, as monomers, at least 40 to 60 mol%, based on the amount of all monomers, of at least one α-olefin of the general formula H 2 C=CH-R 1 where R 1 is at least one linear, cyclic or branched, aliphatic and/or aromatic hydrocarbyl radical having 14 to 50 carbon atoms, and 60 to 40 mol%, based on the amount of all monomers, of monoethylenically unsaturated dicarboxylic acids or derivatives thereof, wherein the monomers are at least one monomer (R 2 OOC)R 5 C=CR 6 (COOR 4), at least one monomer (R 3 OOC)R 5 C=CR 6 (COOR 4) and optionally at least one monomer selected from the group of (HOOC)R 5 C=CR 6 (COOH) (B3a) and where • R 2 is a linear alkyl radical having 16 to 36 carbon atoms, • R 3 is a radical selected from the group consisting of ▪ R 3a: linear 1-alkyl radicals having 1 to 10 carbon atoms, ▪ R 3b: branched and/or secondary alkyl radicals having 4 to 36 carbon atoms, ▪ R 3c: unsubstituted or alkyl-substituted, cyclic alkyl radicals having 5 to 18 carbon atoms, or ▪ R 3d: unsubstituted or alkyl-substituted, aromatic hydrocarbyl radicals having 6 to 36 carbon atoms, • R 4 in each case is a radical selected from the group of H, R 2 and R 3, with the proviso that at least 50 mol% of the R 4 radicals are H, • R 5 and R 6 are each H or methyl, • the proportion of the R 3 radicals based on the sum total of the R 2 and R 3 radicals is 1 mol% to 49 mol%, • the proportion of the monomers + based on the sum total of all monomers is at least 50 mol%, and • the weight-average molecular weight M w of the copolymers is 2000 g/mol to 25 000 g/mol. 40 to 60 mol%, based on the amount of all monomers, of at least one α-olefin of the general formula H 2 C=CH-R 1 where R 1 is at least one linear, cyclic or branched, aliphatic and/or aromatic hydrocarbyl radical having 14 to 50 carbon atoms, and 60 to 40 mol%, based on the amount of all monomers, of monoethylenically unsaturated dicarboxylic acids or derivatives thereof, at least one monomer (R 2 OOC)R 5 C=CR 6 (COOR 4), at least one monomer (R 3 OOC)R 5 C=CR 6 (COOR 4) and optionally at least one monomer selected from the group of (HOOC)R 5 C=CR 6 (COOH) (B3a) and where • R 2 is a linear alkyl radical having 16 to 36 carbon atoms, • R 3 is a radical selected from the group consisting of ▪ R 3a: linear 1-alkyl radicals having 1 to 10 carbon atoms, ▪ R 3b: branched and/or secondary alkyl radicals having 4 to 36 carbon atoms, ▪ R 3c: unsubstituted or alkyl-substituted, cyclic alkyl radicals having 5 to 18 carbon atoms, or ▪ R 3d: unsubstituted or alkyl-substituted, aromatic hydrocarbyl radicals having 6 to 36 carbon atoms, • R 4 in each case is a radical selected from the group of H, R 2 and R 3, with the proviso that at least 50 mol% of the R 4 radicals are H, • R 5 and R 6 are each H or methyl, • the proportion of the R 3 radicals based on the sum total of the R 2 and R 3 radicals is 1 mol% to 49 mol%, • the proportion of the monomers + based on the sum total of all monomers is at least 50 mol%, and • the weight-average molecular weight M w of the copolymers is 2000 g/mol to 25 000 g/mol. • R 2 is a linear alkyl radical having 16 to 36 carbon atoms, • R 3 is a radical selected from the group consisting of ▪ R 3a: linear 1-alkyl radicals having 1 to 10 carbon atoms, ▪ R 3b: branched and/or secondary alkyl radicals having 4 to 36 carbon atoms, ▪ R 3c: unsubstituted or alkyl-substituted, cyclic alkyl radicals having 5 to 18 carbon atoms, or ▪ R 3d: unsubstituted or alkyl-substituted, aromatic hydrocarbyl radicals having 6 to 36 carbon atoms, ▪ R 3a: linear 1-alkyl radicals having 1 to 10 carbon atoms, ▪ R 3b: branched and/or secondary alkyl radicals having 4 to 36 carbon atoms, ▪ R 3c: unsubstituted or alkyl-substituted, cyclic alkyl radicals having 5 to 18 carbon atoms, or ▪ R 3d: unsubstituted or alkyl-substituted, aromatic hydrocarbyl radicals having 6 to 36 carbon atoms, • R 4 in each case is a radical selected from the group of H, R 2 and R 3, with the proviso that at least 50 mol% of the R 4 radicals are H, • R 5 and R 6 are each H or methyl, • the proportion of the R 3 radicals based on the sum total of the R 2 and R 3 radicals is 1 mol% to 49 mol%, • the proportion of the monomers + based on the sum total of all monomers is at least 50 mol%, and • the weight-average molecular weight M w of the copolymers is 2000 g/mol to 25 000 g/mol.