A process for preparing dyed polypropylene-based fibres, the process comprising: i) blending a polypropylene having a Melt Flow Index of 45 g/10 min. or less at 190°C, 2.16 kg with an additive blend to provide a polymer composition, wherein the additive blend consists essentially of: a terpolymer selected from: a first terpolymer of ethylene, acrylic or methacrylic ester and maleic anhydride having a maleic anhydride content of at least 2 % by weight, a second terpolymer of ethylene, acrylic or methacrylic ester and glycidyl methacrylate having a glycidyl methacrylate content of at least 7 % by weight, and mixtures thereof, wherein the terpolymer has a Melt Flow Index of 30 g/10 min. or less at 190°C, 2.16 kg, and an amine-terminated polyamide having a Melt Flow Index of 30 g/10 min. or less at 190°C, 2.16 kg, wherein the weight ratio of terpolymer to amine-terminated polyamide in the additive blend is from 3:1 to 1:1, and wherein the polymer composition comprises from 1 % to 10 % by weight of the additive blend and from 85 % to 99 % by weight of the polypropylene, ii) forming polypropylene-based fibres from the polymer composition, and iii) dyeing the polypropylene-based fibres by contacting the fibres with an aqueous dispersion of a disperse dye. i) blending a polypropylene having a Melt Flow Index of 45 g/10 min. or less at 190°C, 2.16 kg with an additive blend to provide a polymer composition, wherein the additive blend consists essentially of: a terpolymer selected from: a first terpolymer of ethylene, acrylic or methacrylic ester and maleic anhydride having a maleic anhydride content of at least 2 % by weight, a second terpolymer of ethylene, acrylic or methacrylic ester and glycidyl methacrylate having a glycidyl methacrylate content of at least 7 % by weight, and mixtures thereof, wherein the terpolymer has a Melt Flow Index of 30 g/10 min. or less at 190°C, 2.16 kg, and an amine-terminated polyamide having a Melt Flow Index of 30 g/10 min. or less at 190°C, 2.16 kg, wherein the weight ratio of terpolymer to amine-terminated polyamide in the additive blend is from 3:1 to 1:1, and wherein the polymer composition comprises from 1 % to 10 % by weight of the additive blend and from 85 % to 99 % by weight of the polypropylene, a terpolymer selected from: a first terpolymer of ethylene, acrylic or methacrylic ester and maleic anhydride having a maleic anhydride content of at least 2 % by weight, a second terpolymer of ethylene, acrylic or methacrylic ester and glycidyl methacrylate having a glycidyl methacrylate content of at least 7 % by weight, and mixtures thereof, wherein the terpolymer has a Melt Flow Index of 30 g/10 min. or less at 190°C, 2.16 kg, and an amine-terminated polyamide having a Melt Flow Index of 30 g/10 min. or less at 190°C, 2.16 kg, wherein the weight ratio of terpolymer to amine-terminated polyamide in the additive blend is from 3:1 to 1:1, and wherein the polymer composition comprises from 1 % to 10 % by weight of the additive blend and from 85 % to 99 % by weight of the polypropylene, ii) forming polypropylene-based fibres from the polymer composition, and iii) dyeing the polypropylene-based fibres by contacting the fibres with an aqueous dispersion of a disperse dye.