Abstract: The present invention provides an unsaturated polyester resin composition including an unsaturated polyester, a crosslinking agent, an inorganic filling material, a hollow filler, and a fibrous reinforcing material, in which the hollow filler has a content ratio of a hollow filler having a particle diameter of 30 ?m or less of 80 vol % or more with respect to the total volume of the hollow filler, and in which the content of the hollow filler in the unsaturated polyester resin composition is from 15 to 24 mass %. The unsaturated polyester resin composition can provide a molded article having both reduced specific gravity and improved self-tapping strength while maintaining the conventional characteristics (surface smoothness, heat resistance, mechanical strength, dimensional accuracy, and moldability).

Abstract: The present invention provides an unsaturated polyester resin composition including an unsaturated polyester, a crosslinking agent, an inorganic filling material, a hollow filler, and a fibrous reinforcing material, in which the hollow filler has a content ratio of a hollow filler having a particle diameter of 30 ?m or less of 80 vol % or more with respect to the total volume of the hollow filler, and in which the content of the hollow filler in the unsaturated polyester resin composition is from 15 to 24 mass %. The unsaturated polyester resin composition can provide a molded article having both reduced specific gravity and improved self-tapping strength while maintaining the conventional characteristics (surface smoothness, heat resistance, mechanical strength, dimensional accuracy, and moldability).

Abstract: An object of the present invention is to obtain low specific gravity unsaturated polyester resin compositions for lamp reflectors and molded articles thereof, which have a low and invariant specific gravity, and excellent surface smoothness, heat resistance, rigidity, dimensional accuracy, moldability, etc. The compositions comprise from 40 to 210 parts by weight of an inorganic filler having an average particle size of at least 0.5 ?m and from 30 to 160 parts by weight of a hollow filler having a pressure resistance of at least 2,100×104 N/m2 of based on 100 parts by weight of an unsaturated polyester resin and a crosslinking agent wherein the addition ratio by weight of the inorganic filler to the hollow filler lies within a range of 2:8 to 8:2.