Thermoplastic resin composition and molded article thereby

A method of manufacturing an unpainted coated pipe, the method comprising:

• feeding 100 parts by weight of a base resin comprising from 10 to 50% by weight of an acrylate-aromatic vinyl compound-vinyl cyanide compound graft copolymer (A-1) containing acrylate rubber having an average particle diameter of from 0.3 to 0.5 μm, from 5 to 40% by weight of an acrylate-aromatic vinyl compound-vinyl cyanide compound graft copolymer (A-2) containing acrylate rubber having an average particle diameter of from 0.05 μm or more and less than 0.3 μm, and from 20 to 65% by weight of an aromatic vinyl polymer (B), and from 0.5 to 12 parts by weight of a polyamide (C) into an extruder to prepare pellets;
• and
• coextruding the prepared pellets and a steel pipe to manufacture the unpainted coated pipe,
• wherein the unpainted coated pipe has a solvent resistance of 15 days or more, wherein the solvent resistance is measured as time when a crack occurs in a presence of a solvent consisting of 98% by weight of water, 1% by weight of citric acid, and 1% by weight of malic acid.