PURPOSE: To improve the impact resistance and weatherability, by incorporating a copolymer of ethylene and glycidyl ester of an α,β-unsaturated carboxylic acid into polyglutarimide.

CONSTITUTION: 30W99pts.wt. polyglutarimide (A) containing a cyclic imide unit of the formula (where R1, R2, and R3 are each H, an alkyl of 1W20C or an aryl), and 70W1pts.wt. modified polyethylene (B) obtained by copolymerizing 0.1W30wt% glycidyl ester of an α,β-unsaturated carboxylic acid (e.g. glycidyl methacrylate) with ethylene, are compounded to give 100pts.wt. (A+B) in total, obtaining the objective thermoplastic resin composition. In addition, an organic sulfonate (e.g. sodium dodecylbenzenesulfonate) may be incorporated therein to improve the impact resistance and weatherability further.