Thermoplastic polymer composition (P) comprising: (A) 90 to 99.9 wt.-%, based on the total weight of the thermoplastic polymer composition (P), of at least one styrene-based copolymer; (B) 0.1 to 10 wt.-%, based on the total weight of the thermoplastic polymer composition (P), of at least one copolymer composition comprising: (B-1) 75 to 98 wt.-%, preferably 77 to 92 wt.-%, based on the total weight of the copolymer composition (B), of at least one copolymer at least comprising repeating units derived from at least one α-olefin monomer and at least one vinyl-aromatic monomer; (B-2) 1 to 25 wt.-%, preferably 3 to 10 wt.-%, based on the total weight of the copolymer composition (B), of at least one inorganic phosphate compound; and (B-3) 1 to 22 wt.-%, preferably 5 to 20 wt.-%, based on the total weight of the copolymer composition (B), of at least one polyolefin wax; wherein (B-1), (B-2) and (B-3) sum up to 100 wt.-% of the copolymer composition (B) (C) 0 to 9.9 wt.-%, based on the total weight of the thermoplastic polymer composition (P), of at least one colorant, dye or pigment; and (D) 0 to 3 wt.-%, based on the total weight of the thermoplastic polymer composition (P), of at least one further additive, wherein (A), (B), (C) and (D) sum up to 100 wt.-% of the thermoplastic polymer composition (P). (A) 90 to 99.9 wt.-%, based on the total weight of the thermoplastic polymer composition (P), of at least one styrene-based copolymer; (B) 0.1 to 10 wt.-%, based on the total weight of the thermoplastic polymer composition (P), of at least one copolymer composition comprising: (B-1) 75 to 98 wt.-%, preferably 77 to 92 wt.-%, based on the total weight of the copolymer composition (B), of at least one copolymer at least comprising repeating units derived from at least one α-olefin monomer and at least one vinyl-aromatic monomer; (B-2) 1 to 25 wt.-%, preferably 3 to 10 wt.-%, based on the total weight of the copolymer composition (B), of at least one inorganic phosphate compound; and (B-3) 1 to 22 wt.-%, preferably 5 to 20 wt.-%, based on the total weight of the copolymer composition (B), of at least one polyolefin wax; wherein (B-1), (B-2) and (B-3) sum up to 100 wt.-% of the copolymer composition (B) (B-1) 75 to 98 wt.-%, preferably 77 to 92 wt.-%, based on the total weight of the copolymer composition (B), of at least one copolymer at least comprising repeating units derived from at least one α-olefin monomer and at least one vinyl-aromatic monomer; (B-2) 1 to 25 wt.-%, preferably 3 to 10 wt.-%, based on the total weight of the copolymer composition (B), of at least one inorganic phosphate compound; and (B-3) 1 to 22 wt.-%, preferably 5 to 20 wt.-%, based on the total weight of the copolymer composition (B), of at least one polyolefin wax; wherein (B-1), (B-2) and (B-3) sum up to 100 wt.-% of the copolymer composition (B) (C) 0 to 9.9 wt.-%, based on the total weight of the thermoplastic polymer composition (P), of at least one colorant, dye or pigment; and (D) 0 to 3 wt.-%, based on the total weight of the thermoplastic polymer composition (P), of at least one further additive, wherein (A), (B), (C) and (D) sum up to 100 wt.-% of the thermoplastic polymer composition (P). <EOS>